Two-spinor description of massive particles and relativistic spin projection operators

NASA Astrophysics Data System (ADS)

Isaev, A. P.; Podoinitsyn, M. A.

2018-04-01

On the basis of the Wigner unitary representations of the covering group ISL (2 , C) of the Poincaré group, we obtain spin-tensor wave functions of free massive particles with arbitrary spin. The wave functions automatically satisfy the Dirac-Pauli-Fierz equations. In the framework of the two-spinor formalism we construct spin-vectors of polarizations and obtain conditions that fix the corresponding relativistic spin projection operators (Behrends-Fronsdal projection operators). With the help of these conditions we find explicit expressions for relativistic spin projection operators for integer spins (Behrends-Fronsdal projection operators) and then find relativistic spin projection operators for half integer spins. These projection operators determine the numerators in the propagators of fields of relativistic particles. We deduce generalizations of the Behrends-Fronsdal projection operators for arbitrary space-time dimensions D > 2.

Parallel pumping of a ferromagnetic nanostripe: Confinement quantization and off-resonant driving

NASA Astrophysics Data System (ADS)

Yarbrough, P. M.; Livesey, K. L.

2018-01-01

The parametric excitation of spin waves in a rectangular, ferromagnetic nanowire in the parallel pump configuration and with an applied field along the long axis of the wire is studied theoretically, using a semi-classical and semi-analytic Hamiltonian approach. We find that as a function of static applied field strength, there are jumps in the pump power needed to excite thermal spin waves. At these jumps, there is the possibility to non-resonantly excite spin waves near kz = 0. Spin waves with negative or positive group velocity and with different standing wave structures across the wire width can be excited by tuning the applied field. By using a magnetostatic Green's function that depends on both the nanowire's width and thickness—rather than just its aspect ratio—we also find that the threshold field strength varies considerably for nanowires with the same aspect ratio but of different sizes. Comparisons between different methods of calculations are made and the advantages and disadvantages of each are discussed.

Entanglement entropy of critical spin liquids.

PubMed

Zhang, Yi; Grover, Tarun; Vishwanath, Ashvin

2011-08-05

Quantum spin liquids are phases of matter whose internal structure is not captured by a local order parameter. Particularly intriguing are critical spin liquids, where strongly interacting excitations control low energy properties. Here we calculate their bipartite entanglement entropy that characterizes their quantum structure. In particular we calculate the Renyi entropy S(2) on model wave functions obtained by Gutzwiller projection of a Fermi sea. Although the wave functions are not sign positive, S(2) can be calculated on relatively large systems (>324 spins) using the variational Monte Carlo technique. On the triangular lattice we find that entanglement entropy of the projected Fermi sea state violates the boundary law, with S(2) enhanced by a logarithmic factor. This is an unusual result for a bosonic wave function reflecting the presence of emergent fermions. These techniques can be extended to study a wide class of other phases.

Characterizing Bonding Patterns in Diradicals and Triradicals by Density-Based Wave Function Analysis: A Uniform Approach.

PubMed

Orms, Natalie; Rehn, Dirk R; Dreuw, Andreas; Krylov, Anna I

2018-02-13

Density-based wave function analysis enables unambiguous comparisons of the electronic structure computed by different methods and removes ambiguity of orbital choices. We use this tool to investigate the performance of different spin-flip methods for several prototypical diradicals and triradicals. In contrast to previous calibration studies that focused on energy gaps between high- and low spin-states, we focus on the properties of the underlying wave functions, such as the number of effectively unpaired electrons. Comparison of different density functional and wave function theory results provides insight into the performance of the different methods when applied to strongly correlated systems such as polyradicals. We show that canonical molecular orbitals for species like large copper-containing diradicals fail to correctly represent the underlying electronic structure due to highly non-Koopmans character, while density-based analysis of the same wave function delivers a clear picture of the bonding pattern.

Theoretical treatment of the spin-orbit coupling in the rare gas oxides NeO, ArO, KrO, and XeO

NASA Technical Reports Server (NTRS)

Langhoff, S. R.

1980-01-01

Off-diagonal spin-orbit matrix elements are calculated as a function of internuclear distance for the rare gas oxides NeO, ArO, KrO, and XeO using the full microscopic spin-orbit Hamiltonian, including all one- and two-electron integrals, and POL-CI wave functions comparable to those of Dunning and Hay (1977). A good agreement was found when comparing these results in detail with the calculations of Cohen, Wadt and Hay (1979) that utilize an effective one-electron one-center spin-orbit operator. For the rare gas oxide molecules, it is suggested that the numerical results are a more sensitive test of the wave functions (particularly to the extent of charge transfer) than the exact evaluation of all terms in the full spin-orbit operator.

Spin-Multiplet Components and Energy Splittings by Multistate Density Functional Theory.

PubMed

Grofe, Adam; Chen, Xin; Liu, Wenjian; Gao, Jiali

2017-10-05

Kohn-Sham density functional theory has been tremendously successful in chemistry and physics. Yet, it is unable to describe the energy degeneracy of spin-multiplet components with any approximate functional. This work features two contributions. (1) We present a multistate density functional theory (MSDFT) to represent spin-multiplet components and to determine multiplet energies. MSDFT is a hybrid approach, taking advantage of both wave function theory and density functional theory. Thus, the wave functions, electron densities and energy density-functionals for ground and excited states and for different components are treated on the same footing. The method is illustrated on valence excitations of atoms and molecules. (2) Importantly, a key result is that for cases in which the high-spin components can be determined separately by Kohn-Sham density functional theory, the transition density functional in MSDFT (which describes electronic coupling) can be defined rigorously. The numerical results may be explored to design and optimize transition density functionals for configuration coupling in multiconfigurational DFT.

Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Rodriguez, Raul D.; Sheremet, Evgeniya; Deckert-Gaudig, Tanja; Chaneac, Corinne; Hietschold, Michael; Deckert, Volker; Zahn, Dietrich R. T.

2015-05-01

Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm-1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01277e

Spin-Triplet Pairing Induced by Spin-Singlet Interactions in Noncentrosymmetric Superconductors

NASA Astrophysics Data System (ADS)

Matsuzaki, Tomoaki; Shimahara, Hiroshi

2017-02-01

In noncentrosymmetric superconductors, we examine the effect of the difference between the intraband and interband interactions, which becomes more important when the band splitting increases. We define the difference ΔVμ between their coupling constants, i.e., that between the intraband and interband hopping energies of intraband Cooper pairs. Here, the subscript μ of ΔVμ indicates that the interactions scatter the spin-singlet and spin-triplet pairs when μ = 0 and μ = 1,2,3, respectively. It is shown that the strong antisymmetric spin-orbit interaction reverses the target spin parity of the interaction: it converts the spin-singlet and spin-triplet interactions represented by ΔV0 and ΔVμ>0 into effective spin-triplet and spin-singlet pairing interactions, respectively. Hence, for example, triplet pairing can be induced solely by the singlet interaction ΔV0. We name the pairing symmetry of the system after that of the intraband Cooper pair wave function, but with an odd-parity phase factor excluded. The pairing symmetry must then be even, even for the triplet component, and the following results are obtained. When ΔVμ is small, the spin-triplet p-wave interactions induce spin-triplet s-wave and spin-triplet d-wave pairings in the regions where the repulsive singlet s-wave interaction is weak and strong, respectively. When ΔV0 is large, a repulsive interband spin-singlet interaction can stabilize spin-triplet pairing. When the Rashba interaction is adopted for the spin-orbit interaction, the spin-triplet pairing interactions mediated by transverse magnetic fluctuations do not contribute to triplet pairing.

Spin waves in rings of classical magnetic dipoles

NASA Astrophysics Data System (ADS)

Schmidt, Heinz-Jürgen; Schröder, Christian; Luban, Marshall

2017-03-01

We theoretically and numerically investigate spin waves that occur in systems of classical magnetic dipoles that are arranged at the vertices of a regular polygon and interact solely via their magnetic fields. There are certain limiting cases that can be analyzed in detail. One case is that of spin waves as infinitesimal excitations from the system’s ground state, where the dispersion relation can be determined analytically. The frequencies of these infinitesimal spin waves are compared with the peaks of the Fourier transform of the thermal expectation value of the autocorrelation function calculated by Monte Carlo simulations. In the special case of vanishing wave number an exact solution of the equations of motion is possible describing synchronized oscillations with finite amplitudes. Finally, the limiting case of a dipole chain with N\\longrightarrow ∞ is investigated and completely solved.

The "Fermi hole" and the correlation introduced by the symmetrization or the anti-symmetrization of the wave function.

PubMed

Giner, Emmanuel; Tenti, Lorenzo; Angeli, Celestino; Malrieu, Jean-Paul

2016-09-28

The impact of the antisymmetrization is often addressed as a local property of the many-electron wave function, namely that the wave function should vanish when two electrons with parallel spins are in the same position in space. In this paper, we emphasize that this presentation is unduly restrictive: we illustrate the strong non-local character of the antisymmetrization principle, together with the fact that it is a matter of spin symmetry rather than spin parallelism. To this aim, we focus our attention on the simplest representation of various states of two-electron systems, both in atomic (helium atom) and molecular (H 2 and the π system of the ethylene molecule) cases. We discuss the non-local property of the nodal structure of some two-electron wave functions, both using analytical derivations and graphical representations of cuttings of the nodal hypersurfaces. The attention is then focussed on the impact of the antisymmetrization on the maxima of the two-body density, and we show that it introduces strong correlation effects (radial and/or angular) with a non-local character. These correlation effects are analyzed in terms of inflation and depletion zones, which are easily identifiable, thanks to the nodes of the orbitals composing the wave function. Also, we show that the correlation effects induced by the antisymmetrization occur also for anti-parallel spins since all M s components of a given spin state have the same N-body densities. Finally, we illustrate that these correlation effects occur also for the singlet states, but they have strictly opposite impacts: the inflation zones in the triplet become depletion zones in the singlet and vice versa.

Spin-waves in thin films with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Diep, H. T.; El Hog, Sahbi; Puszkarski, Henryk

2018-05-01

Using the Green's function method, we calculate the spin-wave (SW) spectrum in a thin film with quantum Heisenberg spins interacting with each other via an exchange interaction J and a Dzyaloshinskii-Moriya interaction of magnitude D. Due to the competition between J and D, the ground state is non collinear. We show that for large D, the first mode in the SW spectrum is proportional to the in plane wave-vector k at the limit k tending to zero. For small D, it is proportional to k2. We show that the surface modes may occur depending on the surface exchange interaction. We calculate the layer magnetizations at temperature T and the transition temperature as a function of the film thickness.

Omnidirectional spin-wave nanograting coupler

PubMed Central

Yu, Haiming; Duerr, G.; Huber, R.; Bahr, M.; Schwarze, T.; Brandl, F.; Grundler, D.

2013-01-01

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics. PMID:24189978

Controlled rephasing of single spin-waves in a quantum memory based on cold atoms

NASA Astrophysics Data System (ADS)

Farrera, Pau; Albrecht, Boris; Heinze, Georg; Cristiani, Matteo; de Riedmatten, Hugues; Quantum Photonics With Solids; Atoms Team

2015-05-01

Quantum memories for light allow a reversible transfer of quantum information between photons and long lived matter quantum bits. In atomic ensembles, this information is commonly stored in the form of single collective spin excitations (spin-waves). In this work we demonstrate that we can actively control the dephasing of the spin-waves created in a quantum memory based on a cold Rb87 atomic ensemble. The control is provided by an external magnetic field gradient, which induces an inhomogeneous broadening of the atomic hyperfine levels. We show that acting on this gradient allows to control the dephasing of individual spin-waves and to induce later a rephasing. The spin-waves are then mapped into single photons, and we demonstrate experimentally that the active rephasing preserves the sub-Poissonian statistics of the retrieved photons. Finally we show that this rephasing control enables the creation and storage of multiple spin-waves in different temporal modes, which can be selectively readout. This is an important step towards the implementation of a functional temporally multiplexed quantum memory for quantum repeaters. We acknowledge support from the ERC starting grant, the Spanish Ministry of Economy and Competitiveness, the Fondo Europeo de Desarrollo Regional, and the International PhD- fellowship program ``la Caixa''-Severo Ochoa @ICFO.

The role of Snell's law for a magnonic majority gate.

PubMed

Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B; Ross, Caroline A; Takagi, Hiroyuki; Nakamura, Yuichi; Uchida, Hironaga; Inoue, Mitsuteru

2017-08-11

In the fifty years since the postulation of Moore's Law, the increasing energy consumption in silicon electronics has motivated research into emerging devices. An attractive research direction is processing information via the phase of spin waves within magnonic-logic circuits, which function without charge transport and the accompanying heat generation. The functional completeness of magnonic logic circuits based on the majority function was recently proved. However, the performance of such logic circuits was rather poor due to the difficulty of controlling spin waves in the input junction of the waveguides. Here, we show how Snell's law describes the propagation of spin waves in the junction of a Ψ-shaped magnonic majority gate composed of yttrium iron garnet with a partially metallized surface. Based on the analysis, we propose a magnonic counterpart of a core-cladding waveguide to control the wave propagation in the junction. This study has therefore experimentally demonstrated a fundamental building block of a magnonic logic circuit.

Characterizing bonding patterns in diradicals and triradicals by density-based wave function analysis: A uniform approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orms, Natalie; Rehn, Dirk; Dreuw, Andreas

Density-based wave function analysis enables unambiguous comparisons of electronic structure computed by different methods and removes ambiguity of orbital choices. Here, we use this tool to investigate the performance of different spin-flip methods for several prototypical diradicals and triradicals. In contrast to previous calibration studies that focused on energy gaps between high and low spin-states, we focus on the properties of the underlying wave functions, such as the number of effectively unpaired electrons. Comparison of different density functional and wave function theory results provides insight into the performance of the different methods when applied to strongly correlated systems such asmore » polyradicals. We also show that canonical molecular orbitals for species like large copper-containing diradicals fail to correctly represent the underlying electronic structure due to highly non-Koopmans character, while density-based analysis of the same wave function delivers a clear picture of bonding pattern.« less

Characterizing bonding patterns in diradicals and triradicals by density-based wave function analysis: A uniform approach

DOE PAGES

Orms, Natalie; Rehn, Dirk; Dreuw, Andreas; ...

2017-12-21

Density-based wave function analysis enables unambiguous comparisons of electronic structure computed by different methods and removes ambiguity of orbital choices. Here, we use this tool to investigate the performance of different spin-flip methods for several prototypical diradicals and triradicals. In contrast to previous calibration studies that focused on energy gaps between high and low spin-states, we focus on the properties of the underlying wave functions, such as the number of effectively unpaired electrons. Comparison of different density functional and wave function theory results provides insight into the performance of the different methods when applied to strongly correlated systems such asmore » polyradicals. We also show that canonical molecular orbitals for species like large copper-containing diradicals fail to correctly represent the underlying electronic structure due to highly non-Koopmans character, while density-based analysis of the same wave function delivers a clear picture of bonding pattern.« less

Breathers and rogue waves in a Heisenberg ferromagnetic spin chain or an alpha helical protein

NASA Astrophysics Data System (ADS)

Yang, Jin-Wei; Gao, Yi-Tian; Su, Chuan-Qi; Wang, Qi-Min; Lan, Zhong-Zhou

2017-07-01

In this paper, a fourth-order variable-coefficient nonlinear Schrödinger equation for a one-dimensional continuum anisotropic Heisenberg ferromagnetic spin chain or an alpha helical protein has been investigated. Breathers and rogue waves are constructed via the Darboux transformation and generalized Darboux transformation, respectively. Results of the breathers and rogue waves are presented: (1) The first- and second-order Akhmediev breathers and Kuznetsov-Ma solitons are presented with different values of variable coefficients which are related to the energy transfer or higher-order excitations and interactions in the helical protein, or related to the spin excitations resulting from the lowest order continuum approximation and octupole-dipole interaction in a Heisenberg ferromagnetic spin chain, and the nonlinear periodic breathers resulting from the Akhmediev breathers are studied as well; (2) For the first- and second-order rogue waves, we find that they can be split into many similar components when the variable coefficients are polynomial functions of time; (3) Rogue waves can also be split when the variable coefficients are hyperbolic secant functions of time, but the profile of each component in such a case is different.

Gravitational wave searches for aligned-spin binary neutron stars using nonspinning templates

NASA Astrophysics Data System (ADS)

Cho, Hee-Suk; Lee, Chang-Hwan

2018-01-01

We study gravitational wave searches for merging binary neutron stars (NSs). We use nonspinning template waveforms towards the signals emitted from aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the orbital angular momentum. We use the TaylorF2 waveform model, which can generate inspiral waveforms emitted from aligned-spin compact binaries. We employ the single effective spin parameter χeff to represent the effect of two component spins (χ1, χ2) on the wave function. For a target system, we choose a binary consisting of the same component masses of 1.4 M ⊙ and consider the spins up to χ i = 0.4. We investigate fitting factors of the nonspinning templates to evaluate their efficiency in gravitational wave searches for the aligned-spin NS-NS binaries. We find that the templates can achieve the fitting factors exceeding 0.97 only for the signals in the range of -0.2 ≲ χeff ≲ 0. Therefore, we demonstrate the necessity of using aligned-spin templates not to lose the signals outside that range. We also show how much the recovered total mass can be biased from the true value depending on the spin of the signal.

Kinetic analysis of spin current contribution to spectrum of electromagnetic waves in spin-1/2 plasma. I. Dielectric permeability tensor for magnetized plasmas

NASA Astrophysics Data System (ADS)

Andreev, Pavel A.

2017-02-01

The dielectric permeability tensor for spin polarized plasmas is derived in terms of the spin-1/2 quantum kinetic model in six-dimensional phase space. Expressions for the distribution function and spin distribution function are derived in linear approximations on the path of dielectric permeability tensor derivation. The dielectric permeability tensor is derived for the spin-polarized degenerate electron gas. It is also discussed at the finite temperature regime, where the equilibrium distribution function is presented by the spin-polarized Fermi-Dirac distribution. Consideration of the spin-polarized equilibrium states opens possibilities for the kinetic modeling of the thermal spin current contribution in the plasma dynamics.

Gluon amplitudes as 2 d conformal correlators

NASA Astrophysics Data System (ADS)

Pasterski, Sabrina; Shao, Shu-Heng; Strominger, Andrew

2017-10-01

Recently, spin-one wave functions in four dimensions that are conformal primaries of the Lorentz group S L (2 ,C ) were constructed. We compute low-point, tree-level gluon scattering amplitudes in the space of these conformal primary wave functions. The answers have the same conformal covariance as correlators of spin-one primaries in a 2 d CFT. The Britto-Cachazo-Feng-Witten (BCFW) recursion relation between three- and four-point gluon amplitudes is recast into this conformal basis.

Supersymmetric dS/CFT

NASA Astrophysics Data System (ADS)

Hertog, Thomas; Tartaglino-Mazzucchelli, Gabriele; Van Riet, Thomas; Venken, Gerben

2018-02-01

We put forward new explicit realisations of dS/CFT that relate N = 2 supersymmetric Euclidean vector models with reversed spin-statistics in three dimensions to specific supersymmetric Vasiliev theories in four-dimensional de Sitter space. The partition function of the free supersymmetric vector model deformed by a range of low spin deformations that preserve supersymmetry appears to specify a well-defined wave function with asymptotic de Sitter boundary conditions in the bulk. In particular we find the wave function is globally peaked at undeformed de Sitter space, with a low amplitude for strong deformations. This suggests that supersymmetric de Sitter space is stable in higher-spin gravity and in particular free from ghosts. We speculate this is a limiting case of the de Sitter realizations in exotic string theories.

Quantum Critical Point revisited by the Dynamical Mean Field Theory

NASA Astrophysics Data System (ADS)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.

Nuclear spin dependence of time reversal invariance violating effects in neutron scattering

NASA Astrophysics Data System (ADS)

Gudkov, Vladimir; Shimizu, Hirohiko M.

2018-06-01

The spin structure of parity violating and time reversal invariance violating effects in neutron scattering is discussed. The explicit relations between these effects are presented in terms of functions nuclear spins and neutron partial widths of p -wave resonances.

Dynamics of Proton Spin: Role of qqq Force

NASA Astrophysics Data System (ADS)

Mitra, A. N.

The analytic structure of the qqq wave function, obtained recently in the high momentum regime of QCD, is employed for the formulation of baryonic transition amplitudes via quark loops. A new aspect of this study is the role of a direct (Y -shaped, Mercedes-Benz type) qqq force in generating the qqq wave function The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. The dynamics of this 3-body force shows up through a characteristic singularity in the hypergeometric differential equation for the 3D wave function ϕ, corresponding to a negative eigenvalue of the spin operator iσ1·σ2 × σ3 which is an integral part of the qqq force. As a first application of this wave function to the problem of the proton spin anomaly, the two-gluon contribution to the anomaly yields an estimate of the right sign, although somewhat smaller in magnitude.

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions

NASA Astrophysics Data System (ADS)

John, Sajeev; Golubentsev, Andrey

1995-01-01

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector describing traditional spin-density-wave or spiral magnetic states. These one-electron spinor wave functions have the distinguishing property that they are antiperiodic along a closed path encircling any elementary plaquette of the lattice. This corresponds to a 2π rotation of the internal coordinate frame of the electron as it encircles the plaquette. The possibility of spinor wave functions with spatial antiperiodicity is a direct consequence of the two-valuedness of the internal electronic wave function defined on the space of Euler angles describing its spin. This internal space is the topologically, doubly-connected, group manifold of SO(3). Formally, these antiperiodic wave functions may be described by passing a flux which couples to spin (rather than charge) through each of the elementary plaquettes of the lattice. When applied to the two-dimensional Hubbard model with one electron per site, this new topological magnetic state exhibits a relativistic spectrum for charged, quasiparticle excitations with a suppressed one-electron density of states at the Fermi level. For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number μ associated with the vortex rotation of the background magnetic moment field by a phase angle 2πμ along a path encircling the soliton. Such solitons also carry a spin flux of μπ through the plaquette on which they are centered. The μ=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the μ=1 and 2 solitons. The spectrum of localized states is symmetric about E=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less

Wave function, spectrum and effective mass of holes in 2 D quantum antiferromagnet

NASA Astrophysics Data System (ADS)

Su, Zhao-bin; Ll, Yan-min; Lai, Wu-yan; Yu, Lu

1989-12-01

A new quantum Bogoliubov-de Gennes (BdeG) formalism is developed to study the self-consistent motion of holes on an quantum antiferromagnetic (QAFM) background within the generalized t- J model. The local distortion of spin configurations and the renormalization of the hole motion due to virtual excitations of the distorted spin background are treated on an equal footing. The hole wave function and its spectrum, as well as the effective mass for a propagating hole are calculated explicitly.

Breaking Symmetry in Time-Dependent Electronic Structure Theory to Describe Spectroscopic Properties of Non-Collinear and Chiral Molecules

NASA Astrophysics Data System (ADS)

Goings, Joshua James

Time-dependent electronic structure theory has the power to predict and probe the ways electron dynamics leads to useful phenomena and spectroscopic data. Here we report several advances and extensions of broken-symmetry time-dependent electronic structure theory in order to capture the flexibility required to describe non-equilibrium spin dynamics, as well as electron dynamics for chiroptical properties and vibrational effects. In the first half, we begin by discussing the generalization of self-consistent field methods to the so-called two-component structure in order to capture non-collinear spin states. This means that individual electrons are allowed to take a superposition of spin-1/2 projection states, instead of being constrained to either spin-up or spin-down. The system is no longer a spin eigenfunction, and is known a a spin-symmetry broken wave function. This flexibility to break spin symmetry may lead to variational instabilities in the approximate wave function, and we discuss how these may be overcome. With a stable non-collinear wave function in hand, we then discuss how to obtain electronic excited states from the non-collinear reference, along with associated challenges in their physical interpretation. Finally, we extend the two-component methods to relativistic Hamiltonians, which is the proper setting for describing spin-orbit driven phenomena. We describe the first implementation of the explicit time propagation of relativistic two-component methods and how this may be used to capture spin-forbidden states in electronic absorption spectra. In the second half, we describe the extension of explicitly time-propagated wave functions to the simulation of chiroptical properties, namely circular dichroism (CD) spectra of chiral molecules. Natural circular dichroism, that is, CD in the absence of magnetic fields, originates in the broken parity symmetry of chiral molecules. This proves to be an efficient method for computing circular dichroism spectra for high density-of-states chiral molecules. Next, we explore the impact of allowing nuclear motion on electronic absorption spectra within the context of mixed quantum-classical dynamics. We show that nuclear motion modulates the electronic response, and this gives rise to infrared absorption as well as Raman scattering phenomena in the computed dynamic polarizability. Finally, we explore the accuracy of several perturbative approximations to the equation-of-motion coupled-cluster methods for the efficient and accurate prediction of electronic absorption spectra.

Nuclear spin dependence of time reversal invariance violating effects in neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gudkov, Vladimir; Shimizu, Hirohiko M.

In this study, the spin structure of parity violating and time reversal invariance violating effects in neutron scattering is discussed. The explicit relations between these effects are presented in terms of functions nuclear spins and neutron partial widths of p-wave resonances.

Nuclear spin dependence of time reversal invariance violating effects in neutron scattering

DOE PAGES

Gudkov, Vladimir; Shimizu, Hirohiko M.

2018-06-11

In this study, the spin structure of parity violating and time reversal invariance violating effects in neutron scattering is discussed. The explicit relations between these effects are presented in terms of functions nuclear spins and neutron partial widths of p-wave resonances.

Quasiclassical Theory of Spin Dynamics in Superfluid ^3He: Kinetic Equations in the Bulk and Spin Response of Surface Majorana States

NASA Astrophysics Data System (ADS)

Silaev, M. A.

2018-06-01

We develop a theory based on the formalism of quasiclassical Green's functions to study the spin dynamics in superfluid ^3He. First, we derive kinetic equations for the spin-dependent distribution function in the bulk superfluid reproducing the results obtained earlier without quasiclassical approximation. Then, we consider spin dynamics near the surface of fully gapped ^3He-B-phase taking into account spin relaxation due to the transitions in the spectrum of localized fermionic states. The lifetimes of longitudinal and transverse spin waves are calculated taking into account the Fermi-liquid corrections which lead to a crucial modification of fermionic spectrum and spin responses.

Infinite-range Heisenberg model and high-temperature superconductivity

NASA Astrophysics Data System (ADS)

Tahir-Kheli, Jamil; Goddard, William A., III

1993-11-01

A strongly coupled variational wave function, the doublet spin-projected Néel state (DSPN), is proposed for oxygen holes in three-band models of high-temperature superconductors. This wave function has the three-spin system of the oxygen hole plus the two neighboring copper atoms coupled in a spin-1/2 doublet. The copper spins in the neighborhood of a hole are in an eigenstate of the infinite-range Heisenberg antiferromagnet (SPN state). The doublet three-spin magnetic polaron or hopping polaron (HP) is stabilized by the hopping terms tσ and tτ, rather than by the copper-oxygen antiferromagnetic coupling Jpd. Although, the HP has a large projection onto the Emery (Dg) polaron, a non-negligible amount of doublet-u (Du) character is required for optimal hopping stabilization. This is due to Jdd, the copper-copper antiferromagnetic coupling. For the copper spins near an oxygen hole, the copper-copper antiferromagnetic coupling can be considered to be almost infinite ranged, since the copper-spin-correlation length in the superconducting phase (0.06-0.25 holes per in-plane copper) is approximately equal to the mean separation of the holes (between 2 and 4 lattice spacings). The general DSPN wave function is constructed for the motion of a single quasiparticle in an antiferromagnetic background. The SPN state allows simple calculations of various couplings of the oxygen hole with the copper spins. The energy minimum is found at symmetry (π/2,π/2) and the bandwidth scales with Jdd. These results are in agreement with exact computations on a lattice. The coupling of the quasiparticles leads to an attraction of holes and its magnitude is estimated.

Quantum critical point revisited by dynamical mean-field theory

NASA Astrophysics Data System (ADS)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Quantum critical point revisited by dynamical mean-field theory

DOE PAGES

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-31

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less

Estimation of spin contamination error in dissociative adsorption of Au2 onto MgO(0 0 1) surface: First application of approximate spin projection (AP) method to plane wave basis

NASA Astrophysics Data System (ADS)

Tada, Kohei; Koga, Hiroaki; Okumura, Mitsutaka; Tanaka, Shingo

2018-06-01

Spin contamination error in the total energy of the Au2/MgO system was estimated using the density functional theory/plane-wave scheme and approximate spin projection methods. This is the first investigation in which the errors in chemical phenomena on a periodic surface are estimated. The spin contamination error of the system was 0.06 eV. This value is smaller than that of the dissociation of Au2 in the gas phase (0.10 eV). This is because of the destabilization of the singlet spin state due to the weakening of the Au-Au interaction caused by the Au-MgO interaction.

Analysis of Eigenvalue and Eigenfunction of Klein Gordon Equation Using Asymptotic Iteration Method for Separable Non-central Cylindrical Potential

NASA Astrophysics Data System (ADS)

Suparmi, A.; Cari, C.; Lilis Elviyanti, Isnaini

2018-04-01

Analysis of relativistic energy and wave function for zero spin particles using Klein Gordon equation was influenced by separable noncentral cylindrical potential was solved by asymptotic iteration method (AIM). By using cylindrical coordinates, the Klein Gordon equation for the case of symmetry spin was reduced to three one-dimensional Schrodinger like equations that were solvable using variable separation method. The relativistic energy was calculated numerically with Matlab software, and the general unnormalized wave function was expressed in hypergeometric terms.

Spin Bose-metal phase in a spin- (1)/(2) model with ring exchange on a two-leg triangular strip

NASA Astrophysics Data System (ADS)

Sheng, D. N.; Motrunich, Olexei I.; Fisher, Matthew P. A.

2009-05-01

Recent experiments on triangular lattice organic Mott insulators have found evidence for a two-dimensional (2D) spin liquid in close proximity to the metal-insulator transition. A Gutzwiller wave function study of the triangular lattice Heisenberg model with a four-spin ring exchange term appropriate in this regime has found that the projected spinon Fermi sea state has a low variational energy. This wave function, together with a slave particle-gauge theory analysis, suggests that this putative spin liquid possesses spin correlations that are singular along surfaces in momentum space, i.e., “Bose surfaces.” Signatures of this state, which we will refer to as a “spin Bose metal” (SBM), are expected to manifest in quasi-one-dimensional (quasi-1D) ladder systems: the discrete transverse momenta cut through the 2D Bose surface leading to a distinct pattern of 1D gapless modes. Here, we search for a quasi-1D descendant of the triangular lattice SBM state by exploring the Heisenberg plus ring model on a two-leg triangular strip (zigzag chain). Using density matrix renormalization group (DMRG) supplemented by variational wave functions and a bosonization analysis, we map out the full phase diagram. In the absence of ring exchange the model is equivalent to the J1-J2 Heisenberg chain, and we find the expected Bethe-chain and dimerized phases. Remarkably, moderate ring exchange reveals a new gapless phase over a large swath of the phase diagram. Spin and dimer correlations possess singular wave vectors at particular “Bose points” (remnants of the 2D Bose surface) and allow us to identify this phase as the hoped for quasi-1D descendant of the triangular lattice SBM state. We use bosonization to derive a low-energy effective theory for the zigzag spin Bose metal and find three gapless modes and one Luttinger parameter controlling all power law correlations. Potential instabilities out of the zigzag SBM give rise to other interesting phases such as a period-3 valence bond solid or a period-4 chirality order, which we discover in the DMRG. Another interesting instability is into a spin Bose-metal phase with partial ferromagnetism (spin polarization of one spinon band), which we also find numerically using the DMRG.

Excitations in a spin-polarized two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Kreil, Dominik; Hobbiger, Raphael; Drachta, Jürgen T.; Böhm, Helga M.

2015-11-01

A remarkably long-lived spin plasmon may exist in two-dimensional electron liquids with imbalanced spin-up and spin-down population. The predictions for this interesting mode by Agarwal et al. [Phys. Rev. B 90, 155409 (2014), 10.1103/PhysRevB.90.155409] are based on the random phase approximation. Here, we show how to account for spin-dependent correlations from known ground-state pair correlation functions and study the consequences on the various spin-dependent longitudinal response functions. The spin-plasmon dispersion relation and its critical wave vector for Landau damping by minority spins turn out to be significantly lower. We further demonstrate that spin-dependent effective interactions imply a rich structure in the excitation spectrum of the partially spin-polarized system. Most notably, we find a "magnetic antiresonance," where the imaginary part of both, the spin-spin as well as the density-spin response function vanish. The resulting minimum in the double-differential cross section is awaiting experimental confirmation.

Neutron Capture Measurements on 97Mo with the DANCE Array

NASA Astrophysics Data System (ADS)

Walker, Carrie L.

Neutron capture is a process that is crucial to understanding nucleosynthesis, reactors, and nuclear weapons. Precise knowledge of neutron capture cross-sections and level densities is necessary in order to model these high-flux environments. High-confidence spin and parity assignments for neutron resonances are of critical importance to this end. For nuclei in the A=100 mass region, the p-wave neutron strength function is at a maximum, and the s-wave strength function is at a minimum, producing up to six possible Jpi combinations. Parity determination becomes important to assigning spins in this mass region, and the large number of spin groups adds complexity to the problem. In this work, spins and parities for 97Mo resonances are assigned, and best fit models for photon strength function and level density are determined. The neutron capture-cross section for 97Mo is also determined, as are resonance parameters for neutron energies ranging from 16 eV to 2 keV.

Detection of Short-Waved Spin Waves in Individual Microscopic Spin-Wave Waveguides Using the Inverse Spin Hall Effect.

PubMed

Brächer, T; Fabre, M; Meyer, T; Fischer, T; Auffret, S; Boulle, O; Ebels, U; Pirro, P; Gaudin, G

2017-12-13

The miniaturization of complementary metal-oxide-semiconductor (CMOS) devices becomes increasingly difficult due to fundamental limitations and the increase of leakage currents. Large research efforts are devoted to find alternative concepts that allow for a larger data-density and lower power consumption than conventional semiconductor approaches. Spin waves have been identified as a potential technology that can complement and outperform CMOS in complex logic applications, profiting from the fact that these waves enable wave computing on the nanoscale. The practical application of spin waves, however, requires the demonstration of scalable, CMOS compatible spin-wave detection schemes in material systems compatible with standard spintronics as well as semiconductor circuitry. Here, we report on the wave-vector independent detection of short-waved spin waves with wavelengths down to 150 nm by the inverse spin Hall effect in spin-wave waveguides made from ultrathin Ta/Co 8 Fe 72 B 20 /MgO. These findings open up the path for miniaturized scalable interconnects between spin waves and CMOS and the use of ultrathin films made from standard spintronic materials in magnonics.

Temporal evolution of the spin-wave intensity and phase in a local parametric amplifier

NASA Astrophysics Data System (ADS)

Brächer, T.; Heussner, F.; Meyer, T.; Fischer, T.; Geilen, M.; Heinz, B.; Lägel, B.; Hillebrands, B.; Pirro, P.

2018-03-01

We present a time-resolved study of the evolution of the spin-wave intensity and phase in a local parametric spin-wave amplifier at pumping powers close to the threshold of parametric generation. We show that the phase of the amplified spin waves is determined by the phase of the incoming signal-carrying spin waves and that it can be preserved on long time scales as long as the energy input by the input spin waves is provided. In contrast, the phase-information is lost in such a local spin-wave amplifier as soon as the input spin-wave is switched off. These findings are an important benchmark for the use of parametric amplifiers in logic circuits relying on the spin-wave phase as information carrier.

Demonstration of a robust magnonic spin wave interferometer.

PubMed

Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B; Ross, Caroline A; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

2016-07-22

Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe.

Demonstration of a robust magnonic spin wave interferometer

PubMed Central

Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B.; Ross, Caroline A.; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

2016-01-01

Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe. PMID:27443989

Magnon detection using a ferroic collinear multilayer spin valve.

PubMed

Cramer, Joel; Fuhrmann, Felix; Ritzmann, Ulrike; Gall, Vanessa; Niizeki, Tomohiko; Ramos, Rafael; Qiu, Zhiyong; Hou, Dazhi; Kikkawa, Takashi; Sinova, Jairo; Nowak, Ulrich; Saitoh, Eiji; Kläui, Mathias

2018-03-14

Information transport and processing by pure magnonic spin currents in insulators is a promising alternative to conventional charge-current-driven spintronic devices. The absence of Joule heating and reduced spin wave damping in insulating ferromagnets have been suggested for implementing efficient logic devices. After the successful demonstration of a majority gate based on the superposition of spin waves, further components are required to perform complex logic operations. Here, we report on magnetization orientation-dependent spin current detection signals in collinear magnetic multilayers inspired by the functionality of a conventional spin valve. In Y 3 Fe 5 O 12 |CoO|Co, we find that the detection amplitude of spin currents emitted by ferromagnetic resonance spin pumping depends on the relative alignment of the Y 3 Fe 5 O 12 and Co magnetization. This yields a spin valve-like behavior with an amplitude change of 120% in our systems. We demonstrate the reliability of the effect and identify its origin by both temperature-dependent and power-dependent measurements.

Micromagnetic computer simulations of spin waves in nanometre-scale patterned magnetic elements

NASA Astrophysics Data System (ADS)

Kim, Sang-Koog

2010-07-01

Current needs for further advances in the nanotechnologies of information-storage and -processing devices have attracted a great deal of interest in spin (magnetization) dynamics in nanometre-scale patterned magnetic elements. For instance, the unique dynamic characteristics of non-uniform magnetic microstructures such as various types of domain walls, magnetic vortices and antivortices, as well as spin wave dynamics in laterally restricted thin-film geometries, have been at the centre of extensive and intensive researches. Understanding the fundamentals of their unique spin structure as well as their robust and novel dynamic properties allows us to implement new functionalities into existing or future devices. Although experimental tools and theoretical approaches are effective means of understanding the fundamentals of spin dynamics and of gaining new insights into them, the limitations of those same tools and approaches have left gaps of unresolved questions in the pertinent physics. As an alternative, however, micromagnetic modelling and numerical simulation has recently emerged as a powerful tool for the study of a variety of phenomena related to spin dynamics of nanometre-scale magnetic elements. In this review paper, I summarize the recent results of simulations of the excitation and propagation and other novel wave characteristics of spin waves, highlighting how the micromagnetic computer simulation approach contributes to an understanding of spin dynamics of nanomagnetism and considering some of the merits of numerical simulation studies. Many examples of micromagnetic modelling for numerical calculations, employing various dimensions and shapes of patterned magnetic elements, are given. The current limitations of continuum micromagnetic modelling and of simulations based on the Landau-Lifshitz-Gilbert equation of motion of magnetization are also discussed, along with further research directions for spin-wave studies.

Non-volatile Clocked Spin Wave Interconnect for Beyond-CMOS Nanomagnet Pipelines

PubMed Central

Dutta, Sourav; Chang, Sou-Chi; Kani, Nickvash; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.; Naeemi, Azad

2015-01-01

The possibility of using spin waves for information transmission and processing has been an area of active research due to the unique ability to manipulate the amplitude and phase of the spin waves for building complex logic circuits with less physical resources and low power consumption. Previous proposals on spin wave logic circuits have suggested the idea of utilizing the magneto-electric effect for spin wave amplification and amplitude- or phase-dependent switching of magneto-electric cells. Here, we propose a comprehensive scheme for building a clocked non-volatile spin wave device by introducing a charge-to-spin converter that translates information from electrical domain to spin domain, magneto-electric spin wave repeaters that operate in three different regimes - spin wave transmitter, non-volatile memory and spin wave detector, and a novel clocking scheme that ensures sequential transmission of information and non-reciprocity. The proposed device satisfies the five essential requirements for logic application: nonlinearity, amplification, concatenability, feedback prevention, and complete set of Boolean operations. PMID:25955353

Using magnons to probe spintronic materials properties

NASA Astrophysics Data System (ADS)

McMichael, Robert

2012-02-01

For many spin-based electronic devices, from the read sensors in modern hard disk drives to future spintronic logic concepts, the device physics originates in spin polarized currents in ferromagnetic metals. In this talk, I will describe a novel ``Spin Wave Doppler'' method that uses the interaction of spin waves with spin-polarized currents to determine the spin drift velocity and the spin current polarization [1]. Owing to differences between the band structures of majority-spin and minority-spin electrons, the electrical current also carries an angular momentum current and magnetic moment current. Passing these coupled currents though a magnetic wire changes the linear excitations of the magnetization, i.e spin waves. Interestingly, the excitations can be described as drifting ``downstream'' with the electron flow. We measure this drift velocity by monitoring the spin-wave-mediated transmission between pairs of periodically patterned antennas on magnetic wires as a function of current density in the wire. The transmission frequency resonance shifts by 2πδf = vk where the drift velocity v is proportional to both the current density and the current polarization P. I will discuss measurements of the spin polarization of the current in Ni80Fe20 [2], and novel alloys (CoFe)1-xGax [3] and (Ni80Fe20)1-xGdx [4]. [4pt] [1] V. Vlaminck and M. Bailleul, Science, 322, 410 (2008) [0pt] [2] M. Zhu, C. L. Dennis, and R. D. McMichael, Phys. Rev. B, 81, 140407 (2010). [0pt] [3] M. Zhu, B. D. Soe, R. D. McMichael, M. J. Carey, S. Maat, and J. R. Childress, Appl. Phys. Lett., 98, 072510 (2011). [0pt] [4] R. L. Thomas, M. Zhu, C. L. Dennis, V. Misra and R. D. McMichael, J. Appl. Phys., 110, 033902 (2011).

Spin dynamics of qqq wave function on light front in high momentum limit of QCD: Role of qqq force

NASA Astrophysics Data System (ADS)

Mitra, A. N.

2008-04-01

The contribution of a spin-rich qqq force (in conjunction with pairwise qq forces) to the analytical structure of the qqq wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is Coulombic. A distinctive feature of this study is that the spin-rich qqq force is generated by a ggg vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) Y-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function ϕ receives well-defined contributions from the qq and qqq forces. In particular a negative eigenvalue of the spin operator iσ1 · σ2 × σ3 which is an integral part of the qqq force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich qqq force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called 'spin anomaly' of the proton, is a subject of considerable physical interest.

Spin wave scattering and interference in ferromagnetic cross

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nanayakkara, Kasuni; Kozhanov, Alexander; Center for Nano Optics, Georgia State University, Atlanta, Georgia 30303

2015-10-28

Magnetostatic spin wave scattering and interference across a CoTaZr ferromagnetic spin wave waveguide cross junction were investigated experimentally and by micromagnetic simulations. It is observed that the phase of the scattered waves is dependent on the wavelength, geometry of the junction, and scattering direction. It is found that destructive and constructive interference of the spin waves generates switching characteristics modulated by the input phase of the spin waves. Micromagnetic simulations are used to analyze experimental data and simulate the spin wave scattering and interference.

Magnetic droplet soliton nucleation in oblique fields

NASA Astrophysics Data System (ADS)

Mohseni, Morteza; Hamdi, M.; Yazdi, H. F.; Banuazizi, S. A. H.; Chung, S.; Sani, S. R.; Åkerman, Johan; Mohseni, Majid

2018-05-01

We study the auto-oscillating magnetodynamics in orthogonal spin-torque nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic-field angle. In perpendicular fields and at OOP field angles down to approximately 50°, we observe the nucleation of a droplet. However, for field angles below 50°, experiments indicate that the droplet gives way to propagating spin waves, in agreement with our micromagnetic simulations. Theoretical calculations show that the physical mechanism behind these observations is the sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show that the presence of a strong perpendicular magnetic anisotropy free layer in the system reverses the angular dependence of the SWN and dynamics in STNOs with respect to the known behavior determined for the in-plane magnetic anisotropy free layer. Our results are of fundamental interest in understanding the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.

Theory of nonreciprocal spin-wave excitations in spin Hall oscillators with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Zivieri, R.; Giordano, A.; Verba, R.; Azzerboni, B.; Carpentieri, M.; Slavin, A. N.; Finocchio, G.

2018-04-01

A two-dimensional analytical model for the description of the excitation of nonreciprocal spin waves by spin current in spin Hall oscillators in the presence of the interfacial Dzyaloshinskii-Moriya interaction (i -DMI) is developed. The theory allows one to calculate the threshold current for the excitation of spin waves, as well as the frequencies and spatial profiles of the excited spin-wave modes. It is found that the frequency of the excited spin waves exhibits a quadratic redshift with the i -DMI strength. At the same time, in the range of small and moderate values of the i -DMI constant, the averaged wave number of the excited spin waves is almost independent of the i -DMI, which results in a rather weak dependence on the i -DMI of the threshold current of the spin-wave excitation. The obtained analytical results are confirmed by the results of micromagnetic simulations.

Spin wave nonreciprocity for logic device applications

NASA Astrophysics Data System (ADS)

Jamali, Mahdi; Kwon, Jae Hyun; Seo, Soo-Man; Lee, Kyung-Jin; Yang, Hyunsoo

2013-11-01

The utilization of spin waves as eigenmodes of the magnetization dynamics for information processing and communication has been widely explored recently due to its high operational speed with low power consumption and possible applications for quantum computations. Previous proposals of spin wave Mach-Zehnder devices were based on the spin wave phase, a delicate entity which can be easily disrupted. Here, we propose a complete logic system based on the spin wave amplitude utilizing the nonreciprocal spin wave behavior excited by microstrip antennas. The experimental data reveal that the nonreciprocity of magnetostatic surface spin wave can be tuned by the bias magnetic field. Furthermore, engineering of the device structure could result in a high nonreciprocity factor for spin wave logic applications.

Spin wave nonreciprocity for logic device applications

PubMed Central

Jamali, Mahdi; Kwon, Jae Hyun; Seo, Soo-Man; Lee, Kyung-Jin; Yang, Hyunsoo

2013-01-01

The utilization of spin waves as eigenmodes of the magnetization dynamics for information processing and communication has been widely explored recently due to its high operational speed with low power consumption and possible applications for quantum computations. Previous proposals of spin wave Mach-Zehnder devices were based on the spin wave phase, a delicate entity which can be easily disrupted. Here, we propose a complete logic system based on the spin wave amplitude utilizing the nonreciprocal spin wave behavior excited by microstrip antennas. The experimental data reveal that the nonreciprocity of magnetostatic surface spin wave can be tuned by the bias magnetic field. Furthermore, engineering of the device structure could result in a high nonreciprocity factor for spin wave logic applications. PMID:24196318

Electrically tunable g factors in quantum dot molecular spin states.

PubMed

Doty, M F; Scheibner, M; Ponomarev, I V; Stinaff, E A; Bracker, A S; Korenev, V L; Reinecke, T L; Gammon, D

2006-11-10

We present a magnetophotoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in g factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.

Electrically Tunable g Factors in Quantum Dot Molecular Spin States

NASA Astrophysics Data System (ADS)

Doty, M. F.; Scheibner, M.; Ponomarev, I. V.; Stinaff, E. A.; Bracker, A. S.; Korenev, V. L.; Reinecke, T. L.; Gammon, D.

2006-11-01

We present a magnetophotoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in g factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.

Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Luyi

2013-05-17

Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstrationmore » and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly suppressed by electron-electron interactions, leading to remarkable resistance to diffusive spreading of the drifting pulse of spin polarization. Finally, we show that spin helices continue propagate at the same speed as the Fermi sea even when the electron drift velocity exceeds the Fermi velocity of 107 cm s -1.« less

Comment on “Approximate solutions of the Dirac equation for the Rosen-Morse potential including the spin-orbit centrifugal term” [J. Math. Phys. 51, 023525 (2010)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghoumaid, A.; Benamira, F.; Guechi, L.

2016-02-15

It is shown that the application of the Nikiforov-Uvarov method by Ikhdair for solving the Dirac equation with the radial Rosen-Morse potential plus the spin-orbit centrifugal term is inadequate because the required conditions are not satisfied. The energy spectra given is incorrect and the wave functions are not physically acceptable. We clarify the problem and prove that the spinor wave functions are expressed in terms of the generalized hypergeometric functions {sub 2}F{sub 1}(a, b, c; z). The energy eigenvalues for the bound states are given by the solution of a transcendental equation involving the hypergeometric function.

Toward nonlinear magnonics: Intensity-dependent spin-wave switching in insulating side-coupled magnetic stripes

NASA Astrophysics Data System (ADS)

Sadovnikov, A. V.; Odintsov, S. A.; Beginin, E. N.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Nikitov, S. A.

2017-10-01

We demonstrate that the nonlinear spin-wave transport in two laterally parallel magnetic stripes exhibit the intensity-dependent power exchange between the adjacent spin-wave channels. By the means of Brillouin light scattering technique, we investigate collective nonlinear spin-wave dynamics in the presence of magnetodipolar coupling. The nonlinear intensity-dependent effect reveals itself in the spin-wave mode transformation and differential nonlinear spin-wave phase shift in each adjacent magnetic stripe. The proposed analytical theory, based on the coupled Ginzburg-Landau equations, predicts the geometry design involving the reduction of power requirement to the all-magnonic switching. A very good agreement between calculation and experiment was found. In addition, a micromagnetic and finite-element approach has been independently used to study the nonlinear behavior of spin waves in adjacent stripes and the nonlinear transformation of spatial profiles of spin-wave modes. Our results show that the proposed spin-wave coupling mechanism provides the basis for nonlinear magnonic circuits and opens the perspectives for all-magnonic computing architecture.

Spin-transfer torque induced spin waves in antiferromagnetic insulators

DOE PAGES

Daniels, Matthew W.; Guo, Wei; Stocks, George Malcolm; ...

2015-01-01

We explore the possibility of exciting spin waves in insulating antiferromagnetic films by injecting spin current at the surface. We analyze both magnetically compensated and uncompensated interfaces. We find that the spin current induced spin-transfer torque can excite spin waves in insulating antiferromagnetic materials and that the chirality of the excited spin wave is determined by the polarization of the injected spin current. Furthermore, the presence of magnetic surface anisotropy can greatly increase the accessibility of these excitations.

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes.

PubMed

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-08-21

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 10(4). When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 10(6).

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

PubMed Central

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-01-01

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

Spin eigen-states of Dirac equation for quasi-two-dimensional electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eremko, Alexander, E-mail: eremko@bitp.kiev.ua; Brizhik, Larissa, E-mail: brizhik@bitp.kiev.ua; Loktev, Vadim, E-mail: vloktev@bitp.kiev.ua

Dirac equation for electrons in a potential created by quantum well is solved and the three sets of the eigen-functions are obtained. In each set the wavefunction is at the same time the eigen-function of one of the three spin operators, which do not commute with each other, but do commute with the Dirac Hamiltonian. This means that the eigen-functions of Dirac equation describe three independent spin eigen-states. The energy spectrum of electrons confined by the rectangular quantum well is calculated for each of these spin states at the values of energies relevant for solid state physics. It is shownmore » that the standard Rashba spin splitting takes place in one of such states only. In another one, 2D electron subbands remain spin degenerate, and for the third one the spin splitting is anisotropic for different directions of 2D wave vector.« less

Homogeneous microwave field emitted propagating spin waves: Direct imaging and modeling

NASA Astrophysics Data System (ADS)

Lohman, Mathis; Mozooni, Babak; McCord, Jeffrey

2018-03-01

We explore the generation of propagating dipolar spin waves by homogeneous magnetic field excitation in the proximity of the boundaries of magnetic microstructures. Domain wall motion, precessional dynamics, and propagating spin waves are directly imaged by time-resolved wide-field magneto-optical Kerr effect microscopy. The aspects of spin wave generation are clarified by micromagnetic calculations matching the experimental results. The region of dipolar spin wave formation is confined to the local resonant excitation due to non-uniform internal demagnetization fields at the edges of the patterned sample. Magnetic domain walls act as a border for the propagation of plane and low damped spin waves, thus restraining the spin waves within the individual magnetic domains. The findings are of significance for the general understanding of structural and configurational magnetic boundaries for the creation, the propagation, and elimination of spin waves.

Fate of the open-shell singlet ground state in the experimentally accessible acenes: A quantum Monte Carlo study

NASA Astrophysics Data System (ADS)

Dupuy, Nicolas; Casula, Michele

2018-04-01

By means of the Jastrow correlated antisymmetrized geminal power (JAGP) wave function and quantum Monte Carlo (QMC) methods, we study the ground state properties of the oligoacene series, up to the nonacene. The JAGP is the accurate variational realization of the resonating-valence-bond (RVB) ansatz proposed by Pauling and Wheland to describe aromatic compounds. We show that the long-ranged RVB correlations built in the acenes' ground state are detrimental for the occurrence of open-shell diradical or polyradical instabilities, previously found by lower-level theories. We substantiate our outcome by a direct comparison with another wave function, tailored to be an open-shell singlet (OSS) for long-enough acenes. By comparing on the same footing the RVB and OSS wave functions, both optimized at a variational QMC level and further projected by the lattice regularized diffusion Monte Carlo method, we prove that the RVB wave function has always a lower variational energy and better nodes than the OSS, for all molecular species considered in this work. The entangled multi-reference RVB state acts against the electron edge localization implied by the OSS wave function and weakens the diradical tendency for higher oligoacenes. These properties are reflected by several descriptors, including wave function parameters, bond length alternation, aromatic indices, and spin-spin correlation functions. In this context, we propose a new aromatic index estimator suitable for geminal wave functions. For the largest acenes taken into account, the long-range decay of the charge-charge correlation functions is compatible with a quasi-metallic behavior.

Spin Josephson effect in topological superconductor-ferromagnet junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, C. D.; Wang, J., E-mail: jwang@seu.edu.cn

2014-03-21

The composite topological superconductor (TS), made of one-dimensional spin-orbit coupled nanowire with proximity-induced s-wave superconductivity, is not a pure p-wave superconductor but still has a suppressed s-wave pairing. We propose to probe the spin texture of the p-wave pairing in this composite TS by examining possible spin supercurrents in an unbiased TS/ferromagnet junction. It is found that both the exchange-coupling induced and spin-flip reflection induced spin currents exist in the setup and survive even in the topological phase. We showed that besides the nontrivial p-wave pairing state accounting for Majorana Fermions, there shall be a trivial p-wave pairing state thatmore » contributes to spin supercurrent. The trivial p-wave pairing state is diagnosed from the mixing effect between the suppressed s-wave pairing and the topologically nontrivial p-wave pairing. The d vector of the TS is proved not to be rigorously perpendicular to the spin projection of p-wave pairings. Our findings are also confirmed by the Kitaev's p-wave model with a nonzero s-wave pairing.« less

Directional multimode coupler for planar magnonics: Side-coupled magnetic stripes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A.; Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009

We experimentally demonstrate spin waves coupling in two laterally adjacent magnetic stripes. By the means of Brillouin light scattering spectroscopy, we show that the coupling efficiency depends both on the magnonic waveguides' geometry and the characteristics of spin-wave modes. In particular, the lateral confinement of coupled yttrium-iron-garnet stripes enables the possibility of control over the spin-wave propagation characteristics. Numerical simulations (in time domain and frequency domain) reveal the nature of intermodal coupling between two magnonic stripes. The proposed topology of multimode magnonic coupler can be utilized as a building block for fabrication of integrated parallel functional and logic devices suchmore » as the frequency selective directional coupler or tunable splitter, enabling a number of potential applications for planar magnonics.« less

Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

PubMed Central

Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

2016-01-01

Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

Topological Magnonics: A Paradigm for Spin-Wave Manipulation and Device Design

NASA Astrophysics Data System (ADS)

Wang, X. S.; Zhang, H. W.; Wang, X. R.

2018-02-01

Conventional magnonic devices use magnetostatic waves whose properties are sensitive to device geometry and the details of magnetization structure, so the design and the scalability of the device or circuitry are difficult. We propose topological magnonics, in which topological exchange spin waves are used as information carriers, that do not suffer from conventional problems of magnonic devices with additional nice features of nanoscale wavelength and high frequency. We show that a perpendicularly magnetized ferromagnet on a honeycomb lattice is generically a topological magnetic material in the sense that topologically protected chiral edge spin waves exist in the band gap as long as a spin-orbit-induced nearest-neighbor pseudodipolar interaction (and/or a next-nearest-neighbor Dzyaloshinskii-Moriya interaction) is present. The edge spin waves propagate unidirectionally along sample edges and domain walls regardless of the system geometry and defects. As a proof of concept, spin-wave diodes, spin-wave beam splitters, and spin-wave interferometers are designed by using sample edges and domain walls to manipulate the propagation of topologically protected chiral spin waves. Since magnetic domain walls can be controlled by magnetic fields or electric current or fields, one can essentially draw, erase, and redraw different spin-wave devices and circuitry on the same magnetic plate so that the proposed devices are reconfigurable and tunable. The topological magnonics opens up an alternative direction towards a robust, reconfigurable and scalable spin-wave circuitry.

Spin wave propagation in perpendicular magnetized 20 nm Yttrium Iron Garnet with different antenna design

NASA Astrophysics Data System (ADS)

Chen, Jilei; Stueckler, Tobias; Zhang, Youguang; Zhao, Weisheng; Yu, Haiming; Chang, Houchen; Liu, Tao; Wu, Mingzhong; Liu, Chuanpu; Liao, Zhimin; Yu, Dapeng; Fert Beijing research institute Team; Colorado State University Team; Peking University Collaboration

Magnonics offers a new way to transport information using spin waves free of charge current and could lead to a new paradigm in the area of computing. Forward volume (FV) mode spin wave with perpendicular magnetized configuration is suitable for spin wave logic device because it is free of non-reciprocity effect. Here, we study FV mode spin wave propagation in YIG thin film with an ultra-low damping. We integrated differently designed antenna i.e., coplanar waveguide and micro stripline with different dimensions. The k vectors of the spin waves defined by the design of the antenna are calculated using Fourier transform. We show FV mode spin wave propagation results by measuring S12 parameter from vector network analyzer and we extract the group velocity of the FV mode spin wave as well as its dispersion relations.

Magnetic Snell's law and spin-wave fiber with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Yu, Weichao; Lan, Jin; Wu, Ruqian; Xiao, Jiang

2016-10-01

Spin waves are collective excitations propagating in the magnetic medium with ordered magnetizations. Magnonics, utilizing the spin wave (magnon) as an information carrier, is a promising candidate for low-dissipation computation and communication technologies. We discover that, due to the Dzyaloshinskii-Moriya interaction, the scattering behavior of the spin wave at a magnetic domain wall follows a generalized Snell's law, where two magnetic domains work as two different mediums. Similar to optical total reflection that occurs at water-air interfaces, spin waves may experience total reflection at the magnetic domain walls when their incident angle is larger than a critical value. We design a spin-wave fiber using a magnetic domain structure with two domain walls, and demonstrate that such a spin-wave fiber can transmit spin waves over long distances by total internal reflections, in analogy to an optical fiber.

Growth and spin-wave properties of thin Y{sub 3}Fe{sub 5}O{sub 12} films on Si substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stognij, A. I.; Novitskii, N. N.; Lutsev, L. V., E-mail: l-lutsev@mail.ru

2015-07-14

We describe synthesis of submicron Y{sub 3}Fe{sub 5}O{sub 12} (YIG) films sputtered on Si substrates and present results of the investigation of ferromagnetic resonance (FMR) and spin waves in YIG/SiO{sub 2}/Si structures. It is found that decrease of the annealing time leads to essential reduction of the FMR linewidth ΔH and, consequently, to reduction of relaxation losses of spin waves. Spin-wave propagation in in-plane magnetized YIG/SiO{sub 2}/Si structures is studied. We observe the asymmetry of amplitude-frequency characteristics of the Damon-Eshbach spin waves caused by different localizations of spin waves at the free YIG surface and at the YIG/SiO{sub 2} interface.more » Growth of the generating microwave power leads to spin-wave instability and changes amplitude-frequency characteristics of spin waves.« less

High-efficiency control of spin-wave propagation in ultra-thin yttrium iron garnet by the spin-orbit torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evelt, M.; Demidov, V. E., E-mail: demidov@uni-muenster.de; Bessonov, V.

2016-04-25

We study experimentally with submicrometer spatial resolution the propagation of spin waves in microscopic waveguides based on the nanometer-thick yttrium iron garnet and Pt layers. We demonstrate that by using the spin-orbit torque, the propagation length of the spin waves in such systems can be increased by nearly a factor of 10, which corresponds to the increase in the spin-wave intensity at the output of a 10 μm long transmission line by three orders of magnitude. We also show that, in the regime, where the magnetic damping is completely compensated by the spin-orbit torque, the spin-wave amplification is suppressed by themore » nonlinear scattering of the coherent spin waves from current-induced excitations.« less

All-Electrical Measurement of Interfacial Dzyaloshinskii-Moriya Interaction Using Collective Spin-Wave Dynamics.

PubMed

Lee, Jong Min; Jang, Chaun; Min, Byoung-Chul; Lee, Seo-Won; Lee, Kyung-Jin; Chang, Joonyeon

2016-01-13

Dzyaloshinskii-Moriya interaction (DMI), which arises from the broken inversion symmetry and spin-orbit coupling, is of prime interest as it leads to a stabilization of chiral magnetic order and provides an efficient manipulation of magnetic nanostructures. Here, we report all-electrical measurement of DMI using propagating spin wave spectroscopy based on the collective spin wave with a well-defined wave vector. We observe a substantial frequency shift of spin waves depending on the spin chirality in Pt/Co/MgO structures. After subtracting the contribution from other sources to the frequency shift, it is possible to quantify the DMI energy in Pt/Co/MgO systems. The result reveals that the DMI in Pt/Co/MgO originates from the interfaces, and the sign of DMI corresponds to the inversion asymmetry of the film structures. The electrical excitation and detection of spin waves and the influence of interfacial DMI on the collective spin-wave dynamics will pave the way to the emerging field of spin-wave logic devices.

Orbitally excited spectra and decay of cc¯ meson

NASA Astrophysics Data System (ADS)

Chaturvedi, Raghav; Rai, A. K.

2018-05-01

We use the hydrogen like trial wave function for computation of the mass spectra and decay properties of charmonia within the framework of phenomenological quark anti-quark Coulomb plus power potential with varying potential index from 0.5 to 2.0. The spin-spin hyperfine interaction is considered to incorporate splitting of the ground and radially excited states energy levels, further spin-orbit and tensor interactions are employed to calculate the masses of orbitally excited states. We construct the Regge trajectories from the mass spectra in (J, M2) and (nr, M2) planes. We also compute γγ decay width of P wave states of cc¯.

Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gladii, O.; Henry, Y.; Bailleul, M.

2016-05-16

We investigate the effect of an electrical current on the attenuation length of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating spin-wave spectroscopy. The modification of the spin-wave relaxation rate is linear in current density, reaching up to 14% for a current density of 2.3 × 10{sup 11} A/m{sup 2} in Pt. This change is attributed to the spin transfer torque induced by the spin Hall effect and corresponds to an effective spin Hall angle of 0.13, which is among the highest values reported so far. The spin Hall effect thus appears as an efficient way of amplifying/attenuating propagating spin waves.

Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

NASA Astrophysics Data System (ADS)

Balinskiy, Michael; Kargar, Fariborz; Chiang, Howard; Balandin, Alexander A.; Khitun, Alexander G.

2018-05-01

This article reports results of experimental investigation of the spin wave interference over large distances in the Y3Fe2(FeO4)3 waveguide using Brillouin-Mandelstam spectroscopy. Two coherent spin waves are excited by the micro-antennas fabricated at the edges of the waveguide. The amplitudes of the input spin waves are adjusted to provide approximately the same intensity in the central region of the waveguide. The relative phase between the excited spin waves is controlled by the phase shifter. The change of the local intensity distribution in the standing spin wave is monitored using Brillouin-Mandelstam light scattering spectroscopy. Experimental data demonstrate the oscillation of the scattered light intensity depending on the relative phase of the interfering spin waves. The oscillations of the intensity, tunable via the relative phase shift, are observed as far as 7.5 mm away from the spin-wave generating antennas at room temperature. The obtained results are important for developing techniques for remote control of spin currents, with potential applications in spin-based memory and logic devices.

Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.; Institute of Nanomaterial and Nanostructure, Changsha University of Science and Technology, Changsha 410114; Hu, J.

2015-07-20

Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

All-optical observation and reconstruction of spin wave dispersion

PubMed Central

Hashimoto, Yusuke; Daimon, Shunsuke; Iguchi, Ryo; Oikawa, Yasuyuki; Shen, Ka; Sato, Koji; Bossini, Davide; Tabuchi, Yutaka; Satoh, Takuya; Hillebrands, Burkard; Bauer, Gerrit E. W.; Johansen, Tom H.; Kirilyuk, Andrei; Rasing, Theo; Saitoh, Eiji

2017-01-01

To know the properties of a particle or a wave, one should measure how its energy changes with its momentum. The relation between them is called the dispersion relation, which encodes essential information of the kinetics. In a magnet, the wave motion of atomic spins serves as an elementary excitation, called a spin wave, and behaves like a fictitious particle. Although the dispersion relation of spin waves governs many of the magnetic properties, observation of their entire dispersion is one of the challenges today. Spin waves whose dispersion is dominated by magnetostatic interaction are called pure-magnetostatic waves, which are still missing despite of their practical importance. Here, we report observation of the band dispersion relation of pure-magnetostatic waves by developing a table-top all-optical spectroscopy named spin-wave tomography. The result unmasks characteristics of pure-magnetostatic waves. We also demonstrate time-resolved measurements, which reveal coherent energy transfer between spin waves and lattice vibrations. PMID:28604690

Generation of spin waves by a train of fs-laser pulses: a novel approach for tuning magnon wavelength.

PubMed

Savochkin, I V; Jäckl, M; Belotelov, V I; Akimov, I A; Kozhaev, M A; Sylgacheva, D A; Chernov, A I; Shaposhnikov, A N; Prokopov, A R; Berzhansky, V N; Yakovlev, D R; Zvezdin, A K; Bayer, M

2017-07-18

Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with the spectrum of the optically generated spin waves. Here we tackle this problem by launching spin waves by a sequence of femtosecond laser pulses with pulse interval much shorter than the relaxation time of the magnetization oscillations. This leads to the cumulative phenomenon and allows us to generate magnons in a specific narrow range of wavenumbers. The wavelength of spin waves can be tuned from 15 μm to hundreds of microns by sweeping the external magnetic field by only 10 Oe or by slight variation of the pulse repetition rate. Our findings expand the capabilities of the optical spin pump-probe technique and provide a new method for the spin wave generation and control.

Resonant tunneling of spin-wave packets via quantized states in potential wells.

PubMed

Hansen, Ulf-Hendrik; Gatzen, Marius; Demidov, Vladislav E; Demokritov, Sergej O

2007-09-21

We have studied the tunneling of spin-wave pulses through a system of two closely situated potential barriers. The barriers represent two areas of inhomogeneity of the static magnetic field, where the existence of spin waves is forbidden. We show that for certain values of the spin-wave frequency corresponding to the quantized spin-wave states existing in the well formed between the barriers, the tunneling has a resonant character. As a result, transmission of spin-wave packets through the double-barrier structure is much more efficient than the sequent tunneling through two single barriers.

Antiferromagnetic domain wall as spin wave polarizer

NASA Astrophysics Data System (ADS)

Lan, Jin; Yu, Weichao; Xiao, Jiang

Spin waves are collective excitations of local magnetizations that can effectively propagate information even in magnetic insulators. In antiferromagnet, spin waves are endowed with additional polarization freedom. Here we propose that the antiferromagnetic domain wall can act as a spin wave polarizer, which perfectly passes one linearly polarized spin wave while substantially reflects the perpendicular one. We show that the polarizing effect lies in the suppression of one linear polarization inside domain wall, in close analogy to the wire-grid optical polarizer. Our finding opens up new possibilities in magnonic processing by harnessing spin wave polarization in antiferromagnet.

Current-induced modulation of backward spin-waves in metallic microstructures

NASA Astrophysics Data System (ADS)

Sato, Nana; Lee, Seo-Won; Lee, Kyung-Jin; Sekiguchi, Koji

2017-03-01

We performed a propagating spin-wave spectroscopy for backward spin-waves in ferromagnetic metallic microstructures in the presence of electric-current. Even with the smaller current injection of 5× {{10}10} A m-2 into ferromagnetic microwires, the backward spin-waves exhibit a gigantic 200 MHz frequency shift and a 15% amplitude change, showing 60 times larger modulation compared to previous reports. Systematic experiments by measuring dependences on a film thickness of mirowire, on the wave-vector of spin-wave, and on the magnitude of bias field, we revealed that for the backward spin-waves a distribution of internal magnetic field generated by electric-current efficiently modulates the frequency and amplitude of spin-waves. The gigantic frequency and amplitude changes were reproduced by a micromagnetics simulation, predicting that the current-injection of 5× {{10}11} A m-2 allows 3 GHz frequency shift. The effective coupling between electric-current and backward spin-waves has a potential to build up a logic control method which encodes signals into the phase and amplitude of spin-waves. The metallic magnonics cooperating with electronics could suggest highly integrated magnonic circuits both in Boolean and non-Boolean principles.

Spin flip statistics and spin wave interference patterns in Ising ferromagnetic films: A Monte Carlo study.

PubMed

Acharyya, Muktish

2017-07-01

The spin wave interference is studied in two dimensional Ising ferromagnet driven by two coherent spherical magnetic field waves by Monte Carlo simulation. The spin waves are found to propagate and interfere according to the classic rule of interference pattern generated by two point sources. The interference pattern of spin wave is observed in one boundary of the lattice. The interference pattern is detected and studied by spin flip statistics at high and low temperatures. The destructive interference is manifested as the large number of spin flips and vice versa.

Rigid rotators. [deriving the time-independent energy states associated with rotational motions of the molecule

NASA Technical Reports Server (NTRS)

1976-01-01

The two-particle, steady-state Schroedinger equation is transformed to center of mass and internuclear distance vector coordinates, leading to the free particle wave equation for the kinetic energy motion of the molecule and a decoupled wave equation for a single particle of reduced mass moving in a spherical potential field. The latter describes the vibrational and rotational energy modes of the diatomic molecule. For fixed internuclear distance, this becomes the equation of rigid rotator motion. The classical partition function for the rotator is derived and compared with the quantum expression. Molecular symmetry effects are developed from the generalized Pauli principle that the steady-state wave function of any system of fundamental particles must be antisymmetric. Nuclear spin and spin quantum functions are introduced and ortho- and para-states of rotators, along with their degeneracies, are defined. Effects of nuclear spin on entropy are deduced. Next, rigid polyatomic rotators are considered and the partition function for this case is derived. The patterns of rotational energy levels for nonlinear molecules are discussed for the spherical symmetric top, for the prolate symmetric top, for the oblate symmetric top, and for the asymmetric top. Finally, the equilibrium energy and specific heat of rigid rotators are derived.

Gravity dual of spin and charge density waves

NASA Astrophysics Data System (ADS)

Jokela, Niko; Järvinen, Matti; Lippert, Matthew

2014-12-01

At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.

On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhendong; Xiao, Yunlong; Liu, Wenjian, E-mail: liuwjbdf@gmail.com

2014-08-07

The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α{supmore » 2} in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α{sup 2}) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections.« less

On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties

NASA Astrophysics Data System (ADS)

Li, Zhendong; Xiao, Yunlong; Liu, Wenjian

2014-08-01

The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α2 in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α ^2) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections.

Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets

NASA Astrophysics Data System (ADS)

dos Santos, Flaviano José; dos Santos Dias, Manuel; Guimarães, Filipe Souza Mendes; Bouaziz, Juba; Lounis, Samir

2018-01-01

Topological noncollinear magnetic phases of matter are at the heart of many proposals for future information nanotechnology, with novel device concepts based on ultrathin films and nanowires. Their operation requires understanding and control of the underlying dynamics, including excitations such as spin waves. So far, no experimental technique has attempted to probe large wave-vector spin waves in noncollinear low-dimensional systems. In this paper, we explain how inelastic electron scattering, being suitable for investigations of surfaces and thin films, can detect the collective spin-excitation spectra of noncollinear magnets. To reveal the particularities of spin waves in such noncollinear samples, we propose the usage of spin-polarized electron-energy-loss spectroscopy augmented with a spin analyzer. With the spin analyzer detecting the polarization of the scattered electrons, four spin-dependent scattering channels are defined, which allow us to filter and select specific spin-wave modes. We take as examples a topological nontrivial skyrmion lattice, a spin-spiral phase, and the conventional ferromagnet. Then we demonstrate that, counterintuitively and in contrast to the ferromagnetic case, even non-spin-flip processes can generate spin waves in noncollinear substrates. The measured dispersion and lifetime of the excitation modes permit us to fingerprint the magnetic nature of the substrate.

Phase-to-intensity conversion of magnonic spin currents and application to the design of a majority gate

PubMed Central

Brächer, T.; Heussner, F.; Pirro, P.; Meyer, T.; Fischer, T.; Geilen, M.; Heinz, B.; Lägel, B.; Serga, A. A.; Hillebrands, B.

2016-01-01

Magnonic spin currents in the form of spin waves and their quanta, magnons, are a promising candidate for a new generation of wave-based logic devices beyond CMOS, where information is encoded in the phase of travelling spin-wave packets. The direct readout of this phase on a chip is of vital importance to couple magnonic circuits to conventional CMOS electronics. Here, we present the conversion of the spin-wave phase into a spin-wave intensity by local non-adiabatic parallel pumping in a microstructure. This conversion takes place within the spin-wave system itself and the resulting spin-wave intensity can be conveniently transformed into a DC voltage. We also demonstrate how the phase-to-intensity conversion can be used to extract the majority information from an all-magnonic majority gate. This conversion method promises a convenient readout of the magnon phase in future magnon-based devices. PMID:27905539

Spin-wave-driven high-speed domain-wall motions in soft magnetic nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jaehak; Yoo, Myoung-Woo; Kim, Sang-Koog, E-mail: sangkoog@snu.ac.kr

We report on a micromagnetic simulation study of interactions between propagating spin waves and a head-to-head domain wall in geometrically confined magnetic nanotubes. We found that incident spin waves of specific frequencies can lead to sufficiently high-speed (on the order of a few hundreds of m/s or higher) domain-wall motions in the same direction as that of the incident spin-waves. The domain-wall motions and their speed vary remarkably with the frequency and the amplitude of the incident spin-waves. High-speed domain-wall motions originate from the transfer torque of spin waves' linear momentum to the domain wall, through the partial or completemore » reflection of the incident spin waves from the domain wall. This work provides a fundamental understanding of the interaction of the spin waves with a domain wall in the magnetic nanotubes as well as a route to all-magnetic control of domain-wall motions in the magnetic nanoelements.« less

Spectrum Gaps of Spin Waves Generated by Interference in a Uniform Nanostripe Waveguide

PubMed Central

Wang, Qi; Zhang, Huaiwu; Ma, Guokun; Liao, Yulong; Tang, Xiaoli; Zhong, Zhiyong

2014-01-01

We studied spin waves excited by two or more excitation sources in a uniform nanostripe waveguide without periodic structures. Several distinct spectrum gaps formed by spin waves interference rather than by Bragg reflection were observed. We found the center frequency and the number of spectrum gaps of spin waves can be controlled by modulating the distance, number and width of the excitation sources. The results obtained by micromagnetic simulations agree well with that of analytical calculations. Our work therefore paves a new way to control the spectrum gaps of spin waves, which is promising for future spin wave-based devices. PMID:25082001

Antiferromagnetic domain wall as spin wave polarizer and retarder.

PubMed

Lan, Jin; Yu, Weichao; Xiao, Jiang

2017-08-02

As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials. Like the manipulation of its optical counterpart, the ability to manipulate spin wave polarization is not only important but also fundamental for magnonics. With only one type of magnetic lattice, ferromagnets can only accommodate the right-handed circularly polarized spin wave modes, which leaves no freedom for polarization manipulation. In contrast, antiferromagnets, with two opposite magnetic sublattices, have both left and right-circular polarizations, and all linear and elliptical polarizations. Here we demonstrate theoretically and confirm by micromagnetic simulations that, in the presence of Dzyaloshinskii-Moriya interaction, an antiferromagnetic domain wall acts naturally as a spin wave polarizer or a spin wave retarder (waveplate). Our findings provide extremely simple yet flexible routes toward magnonic information processing by harnessing the polarization degree of freedom of spin wave.Spin waves are promising candidates as carriers for energy-efficient information processing, but they have not yet been fully explored application wise. Here the authors theoretically demonstrate that antiferromagnetic domain walls are naturally spin wave polarizers and retarders, two key components of magnonic devices.

Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

NASA Astrophysics Data System (ADS)

Mohseni, S. Morteza; Yazdi, H. F.; Hamdi, M.; Brächer, T.; Mohseni, S. Majid

2018-03-01

Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.

SU (N ) spin-wave theory: Application to spin-orbital Mott insulators

NASA Astrophysics Data System (ADS)

Dong, Zhao-Yang; Wang, Wei; Li, Jian-Xin

2018-05-01

We present the application of the SU (N ) spin-wave theory to spin-orbital Mott insulators whose ground states exhibit magnetic orders. When taking both spin and orbital degrees of freedom into account rather than projecting Hilbert space onto the Kramers doublet, which is the lowest spin-orbital locked energy levels, the SU (N ) spin-wave theory should take the place of the SU (2 ) one due to the inevitable spin-orbital multipole exchange interactions. To implement the application, we introduce an efficient general local mean-field method, which involves all local fluctuations, and develop the SU (N ) linear spin-wave theory. Our approach is tested firstly by calculating the multipolar spin-wave spectra of the SU (4 ) antiferromagnetic model. Then, we apply it to spin-orbital Mott insulators. It is revealed that the Hund's coupling would influence the effectiveness of the isospin-1 /2 picture when the spin-orbital coupling is not large enough. We further carry out the SU (N ) spin-wave calculations of two materials, α -RuCl3 and Sr2IrO4 , and find that the magnonic and spin-orbital excitations are consistent with experiments.

Dependence of Tc on the q -ω structure of the spin-fluctuation spectrum

NASA Astrophysics Data System (ADS)

Dahm, Thomas; Scalapino, D. J.

2018-05-01

A phenomenological spin-fluctuation analysis [Dahm et al., Nat. Phys. 5, 217 (2009), 10.1038/nphys1180], based upon inelastic neutron scattering (INS) and angular resolved photoemission spectroscopy (ARPES) data for YBCO6.6(Tc=61 K) , is used to calculate the functional derivative of the d -wave eigenvalue λd of the linearized gap equation with respect to the imaginary part of the spin susceptibility χ''(q ,ω ) at 70 K. For temperatures near Tc, the variation of Tc with respect to χ''(q ,ω ) is proportional to this functional derivative. We find that above an energy ˜4 Tc the functional derivative becomes positive so that adding spin-fluctuation spectral weight at higher frequencies leads to an increase in Tc. The strongest pairing occurs for large momentum transfers, and small momentum spin-fluctuations suppress the pairing.

Quantum dust magnetosonic waves with spin and exchange correlation effects

NASA Astrophysics Data System (ADS)

Maroof, R.; Mushtaq, A.; Qamar, A.

2016-01-01

Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.).

Relationship between the transverse-field Ising model and the X Y model via the rotating-wave approximation

NASA Astrophysics Data System (ADS)

Kiely, Thomas G.; Freericks, J. K.

2018-02-01

In a large transverse field, there is an energy cost associated with flipping spins along the axis of the field. This penalty can be employed to relate the transverse-field Ising model in a large field to the X Y model in no field (when measurements are performed at the proper stroboscopic times). We describe the details for how this relationship works and, in particular, we also show under what circumstances it fails. We examine wave-function overlap between the two models and observables, such as spin-spin Green's functions. In general, the mapping is quite robust at short times, but will ultimately fail if the run time becomes too long. There is also a tradeoff between the length of time one can run a simulation out to and the time jitter of the stroboscopic measurements that must be balanced when planning to employ this mapping.

Influence of interfacial Dzyaloshinskii-Moriya interaction on the parametric amplification of spin waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verba, Roman, E-mail: verrv@ukr.net; Tiberkevich, Vasil; Slavin, Andrei

2015-09-14

The influence of the interfacial Dzyaloshinskii-Moriya interaction (IDMI) on the parametric amplification of spin waves propagating in ultrathin ferromagnetic film is considered theoretically. It is shown that the IDMI changes the relation between the group velocities of the signal and idler spin waves in a parametric amplifier, which may result in the complete vanishing of the reversed idler wave. In the optimized case, the idler spin wave does not propagate from the pumping region at all, which increases the efficiency of the amplification of the signal wave and suppresses the spurious impact of the idler waves on neighboring spin-wave processingmore » devices.« less

Control of the Spin Angular Momentum and Orbital Angular Momentum of a Reflected Wave by Multifunctional Graphene Metasurfaces.

PubMed

Zhang, Chen; Deng, Li; Zhu, Jianfeng; Hong, Weijun; Wang, Ling; Yang, Wenjie; Li, Shufang

2018-06-21

Three kinds of multifunctional graphene metasurfaces based on Pancharatnam⁻Berry (PB) phase cells are proposed and numerically demonstrated to control a reflected wave’s spin angular momentum (SAM) and orbital angular momentum (OAM) in the terahertz (THz) regime. Each proposed metasurface structure is composed of an array of graphene strips with different deviation angles and a back-grounded quartz substrate. In order to further help readers have a deeper insight into the graphene-based metasurfaces, a detailed design strategy is also provided. With the aid of the designed graphene elements, the proposed metasurfaces can achieve the full 360° range of phase coverage and provide manipulation of SAM and OAM of a circularly polarized (CP) wave at will. More importantly, simultaneous control of these two momentums can also be realized, and in order to demonstrate this function, a THz spin-controlled OAM beam generator with diverse topological charges is created, which can provide one more degree of freedom to improve the channel capability without increasing the bandwidth compared to a linearly polarized (LP) OAM beam. Numerical results verify the proposed graphene metasurfaces, which pave the way for generating spin OAM vortex waves for THz communication systems.

Ferromagnetic resonance in a topographically modulated permalloy film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sklenar, J.; Tucciarone, P.; Lee, R. J.

2015-04-01

A major focus within the field of magnonics involves the manipulation and control spin wave modes. This is usually done by patterning continuous soft magnetic films. Here, we report on work in which we use topographic modifications of a continuous magnetic thin film, rather than lithographic patterning techniques, to modify the magnon spectrum. To demonstrate this technique we have performed in-plane, broad-band, ferromagnetic res- onance studies on a 100 nm Permalloy film sputtered unto a colloidal crystal with individual sphere diameters of 200 nm. Effects resulting from the, ideally, six-fold symmetric underlying colloidal crystal were studied as a function ofmore » the in plane field angle through experiment and micromagnetic modeling. Experimentally, we find two primary spin wave modes; the ratio of the amplitude of these two modes exhibits a six-fold dependence. Modeling shows that both modes are fundamental modes that are nodeless in the unit cell but reside in different demagnetized regions of the unit cell. Additionally, modeling suggests the presence of new higher order topographically modified spin wave modes. Our results demonstrate that topographic modification of magnetic thin films opens new directions for manipulating spin wave modes.« less

Influence of the Verwey Transition on the Spin-Wave Dispersion of Magnetite

DOE Office of Scientific and Technical Information (OSTI.GOV)

McQueeny, R. J.; Yethiraj, Mohana; Montfrooij, W.

Inelastic neutron-scattering measurements of the spin-wave spectrum of magnetite (Fe{sub 3}O{sub 4}) that shed new light on the Verwey transition problem are presented. Above the Verwey transition, the spin waves can fit a simple Heisenberg model. Below TV, a large gap (8?meV) forms in the acoustic spin-wave branch at q = (0,0,1/2) and E = 43?meV. Heisenberg models with large unit cells were used to examine the spin waves when the superexchange is modified to reflect the crystallographic symmetry lowering due to either atomic distortions or charge ordering and find that neither of these models predicts the spin-wave gap.

Bound state solution of Dirac equation for 3D harmonics oscillator plus trigonometric scarf noncentral potential using SUSY QM approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cari, C., E-mail: carinln@yahoo.com; Suparmi, A., E-mail: carinln@yahoo.com

2014-09-30

Dirac equation of 3D harmonics oscillator plus trigonometric Scarf non-central potential for spin symmetric case is solved using supersymmetric quantum mechanics approach. The Dirac equation for exact spin symmetry reduces to Schrodinger like equation. The relativistic energy and wave function for spin symmetric case are simply obtained using SUSY quantum mechanics method and idea of shape invariance.

Transverse Momentum Distributions of Electron in Simulated QED Model

NASA Astrophysics Data System (ADS)

Kaur, Navdeep; Dahiya, Harleen

2018-05-01

In the present work, we have studied the transverse momentum distributions (TMDs) for the electron in simulated QED model. We have used the overlap representation of light-front wave functions where the spin-1/2 relativistic composite system consists of spin-1/2 fermion and spin-1 vector boson. The results have been obtained for T-even TMDs in transverse momentum plane for fixed value of longitudinal momentum fraction x.

Spin-component-scaled Møller-Plesset (SCS-MP) perturbation theory: a generalization of the MP approach with improved properties.

PubMed

Fink, Reinhold F

2010-11-07

A rigorous perturbation theory is proposed, which has the same second order energy as the spin-component-scaled Møller-Plesset second order (SCS-MP2) method of Grimme [J. Chem. Phys. 118, 9095 (2003)]. This upgrades SCS-MP2 to a systematically improvable, true wave-function-based method. The perturbation theory is defined by an unperturbed Hamiltonian, Ĥ(0), that contains the ordinary Fock operator and spin operators Ŝ(2) that act either on the occupied or the virtual orbital spaces. Two choices for Ĥ(0) are discussed and the importance of a spin-pure Ĥ((0)) is underlined. Like the SCS-MP2 approach, the theory contains two parameters (c(os) and c(ss)) that scale the opposite-spin and the same-spin contributions to the second order perturbation energy. It is shown that these parameters can be determined from theoretical considerations by a Feenberg scaling approach or a fit of the wave functions from the perturbation theory to the exact one from a full configuration interaction calculation. The parameters c(os)=1.15 and c(ss)=0.75 are found to be optimal for a reasonable test set of molecules. The meaning of these parameters and the consequences following from a well defined improved MP method are discussed.

Giant titanium electron wave function in gallium oxide: A potential electron-nuclear spin system for quantum information processing

NASA Astrophysics Data System (ADS)

Mentink-Vigier, Frédéric; Binet, Laurent; Vignoles, Gerard; Gourier, Didier; Vezin, Hervé

2010-11-01

The hyperfine interactions of the unpaired electron with eight surrounding G69a and G71a nuclei in Ti-doped β-Ga2O3 were analyzed by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies. They are dominated by strong isotropic hyperfine couplings due to a direct Fermi contact interaction with Ga nuclei in octahedral sites of rutile-type chains oriented along b axis, revealing a large anisotropic spatial extension of the electron wave function. Titanium in β-Ga2O3 is thus best described as a diffuse (Ti4+-e-) pair rather than as a localized Ti3+ . Both electron and G69a nuclear spin Rabi oscillations could be observed by pulsed EPR and pulsed ENDOR, respectively. The electron spin decoherence time is about 1μs (at 4 K) and an upper bound of 520μs (at 8 K) is estimated for the nuclear decoherence time. Thus, β-Ga2O3:Ti appears to be a potential spin-bus system for quantum information processing with a large nuclear spin quantum register.

Persistence of the gapless spin liquid in the breathing kagome Heisenberg antiferromagnet

NASA Astrophysics Data System (ADS)

Iqbal, Yasir; Poilblanc, Didier; Thomale, Ronny; Becca, Federico

2018-03-01

The nature of the ground state of the spin S =1 /2 Heisenberg antiferromagnet on the kagome lattice with breathing anisotropy (i.e., with different superexchange couplings J▵ and J▿ within elementary up- and down-pointing triangles) is investigated within the framework of Gutzwiller projected fermionic wave functions and Monte Carlo methods. We analyze the stability of the U(1 ) Dirac spin liquid with respect to the presence of fermionic pairing that leads to a gapped Z2 spin liquid. For several values of the ratio J▿/J▵ , the size scaling of the energy gain due to the pairing fields and the variational parameters are reported. Our results show that the energy gain of the gapped spin liquid with respect to the gapless state either vanishes for large enough system size or scales to zero in the thermodynamic limit. Similarly, the optimized pairing amplitudes (responsible for opening the spin gap) are shown to vanish in the thermodynamic limit. Our outcome is corroborated by the application of one and two Lanczos steps to the gapless and gapped wave functions, for which no energy gain of the gapped state is detected when improving the quality of the variational states. Finally, we discuss the competition with the "simplex" Z2 resonating-valence-bond spin liquid, valence-bond crystal, and nematic states in the strongly anisotropic regime, i.e., J▿≪J▵ .

Single Spin Superconductivity: Bulk and Junction Effects

NASA Astrophysics Data System (ADS)

Rudd, Robert E.; Pickett, Warren E.

1998-03-01

The Josephson Effect provides a primary signature of single spin superconductivity (SSS), the as yet unobserved superconducting state which was proposed recently(W.E. Pickett, Phys. Rev. Lett. 77), 3185 (1996). as a low temperature phase of half-metallic antiferromagnets.(W.E. Pickett, ``Spin Density Functional Based Search for Half-Metallic Antiferromagnets,'' cond-mat/9709100 (1997).) These materials are insulating in the spin-down channel but are metallic in the spin-up channel. The SSS state is characterized by a unique form of p-wave pairing within a single spin channel.(R.E. Rudd and W.E. Pickett, ``Single Spin Superconductivity:Formulation and Ginzburg-Landau Theory,'' Phys. Rev. B. in press) We develop the theory of a rich variety of Josephson effects that arise due to the form of the SSS order parameter. Tunneling is allowed at a SSS-SSS^' junction depending on the relative orientation of each of their order parameters (SSS and HM AFM). No current flows between an SSS and an s-wave BCS system, which provides a powerful method to distinguish SSS from other superconducting states.

"Magnon Spintronics"

NASA Astrophysics Data System (ADS)

Yu, Haiming; Xiao, Jiang; Pirro, Philipp

2018-03-01

We are proud to present a collection of 12 cutting-edge research articles on the emerging field "magnon spintronics" investigating the properties of spin waves or magnons towards their potential applications in low-power-consumption information technologies. Magnons (quasiparticles of spin waves) are collective excitations of magnetizations in a magnetic system. The concept for such excitations was first introduced 1930 by Felix Bloch [1] who described ferromagnetism in a lattice. The field of magnon spintronics [2] or magnonics [3] aims at utilizing magnons to realize information processing and storage. The propagation of spin waves is free of charge transport, hence a successful realization of magnonic devices can innately avoid Joule heating induced energy loss in nowadays micro- or nano-electronic devices. Magnonics has made many progresses in recent years, including the demonstration of magnonic logic devices [4]. Towards the aim to generate magnonic devices, it is an essential step to find materials suitable for conveying spin waves. One outstanding candidate is a ferromagnetic insulator yttrium iron garnet (YIG). It offers an out standing low damping which allows the propagation of spin waves over relatively long distances. Experiments on such a thin YIG film with an out-of-plane magnetization have been performed by Chen et al. [5]. They excited so called forward volume mode spin waves and determined the propagating spin wave properties, such as the group velocities. Lohman et al. [6] has successfully imaged the propagating spin waves using time-resolved MOKE microscopy and show agreement with micromagnetic modellings. For very long time, YIG is the most ideal material for spin waves thanks to its ultra-low damping. However, it remains a major challenge integrate YIG on to Silicon substrate. Magnetic Heusler alloys on the other hand, can be easily grown on Si substrate and also shows reasonably good damping properties, which allow spin waves to propagate over a distance as long as 100 μm demonstrated by Stueckler et al. [7]. This is so far a record of spin wave propagation distance in ferromagnetic Heusler alloy thin films. Jaroslaw et al. [8] studied spin waves in planar quasicrystal of Penrose tiling showing distinctive magnonic gaps. This proves the impact of quasiperiodic long-range order on the spectrum of spin waves.

Micro-focused Brillouin light scattering study of the magnetization dynamics driven by Spin Hall effect in a transversely magnetized NiFe nanowire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madami, M., E-mail: marco.madami@fisica.unipg.it; Carlotti, G.; Gubbiotti, G.

2015-05-07

We employed micro-focused Brillouin light scattering to study the amplification of the thermal spin wave eigenmodes by means of a pure spin current, generated by the spin-Hall effect, in a transversely magnetized Pt(4 nm)/NiFe(4 nm)/SiO{sub 2}(5 nm) layered nanowire with lateral dimensions 500 × 2750 nm{sup 2}. The frequency and the cross section of both the center (fundamental) and the edge spin wave modes have been measured as a function of the intensity of the injected dc electric current. The frequency of both modes exhibits a clear redshift while their cross section is greatly enhanced on increasing the intensity of the injected dc. A threshold-like behaviormore » is observed for a value of the injected dc of 2.8 mA. Interestingly, an additional mode, localized in the central part of the nanowire, appears at higher frequency on increasing the intensity of the injected dc above the threshold value. Micromagnetic simulations were used to quantitatively reproduce the experimental results and to investigate the complex non-linear dynamics induced by the spin-Hall effect, including the modification of the spatial profile of the spin wave modes and the appearance of the extra mode above the threshold.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru; Kuz’menkov, L.S., E-mail: lsk@phys.msu.ru

We consider quantum plasmas of electrons and motionless ions. We describe separate evolution of spin-up and spin-down electrons. We present corresponding set of quantum hydrodynamic equations. We assume that plasmas are placed in an uniform external magnetic field. We account different occupation of spin-up and spin-down quantum states in equilibrium degenerate plasmas. This effect is included via equations of state for pressure of each species of electrons. We study oblique propagation of longitudinal waves. We show that instead of two well-known waves (the Langmuir wave and the Trivelpiece–Gould wave), plasmas reveal four wave solutions. New solutions exist due to bothmore » the separate consideration of spin-up and spin-down electrons and different occupation of spin-up and spin-down quantum states in equilibrium state of degenerate plasmas.« less

Mass-number and excitation-energy dependence of the spin cutoff parameter

DOE PAGES

Grimes, S. M.; Voinov, A. V.; Massey, T. N.

2016-07-12

Here, the spin cutoff parameter determining the nuclear level density spin distribution ρ(J) is defined through the spin projection as < J 2 z > 1/2 or equivalently for spherical nuclei, (< J(J+1) >/3) 1/2. It is needed to divide the total level density into levels as a function of J. To obtain the total level density at the neutron binding energy from the s-wave resonance count, the spin cutoff parameter is also needed. The spin cutoff parameter has been calculated as a function of excitation energy and mass with a super-conducting Hamiltonian. Calculations have been compared with two commonlymore » used semiempirical formulas. A need for further measurements is also observed. Some complications for deformed nuclei are discussed. The quality of spin cut off parameter data derived from isomeric ratio measurement is examined.« less

Calculation of the exchange coupling constants of copper binuclear systems based on spin-flip constricted variational density functional theory.

PubMed

Zhekova, Hristina R; Seth, Michael; Ziegler, Tom

2011-11-14

We have recently developed a methodology for the calculation of exchange coupling constants J in weakly interacting polynuclear metal clusters. The method is based on unrestricted and restricted second order spin-flip constricted variational density functional theory (SF-CV(2)-DFT) and is here applied to eight binuclear copper systems. Comparison of the SF-CV(2)-DFT results with experiment and with results obtained from other DFT and wave function based methods has been made. Restricted SF-CV(2)-DFT with the BH&HLYP functional yields consistently J values in excellent agreement with experiment. The results acquired from this scheme are comparable in quality to those obtained by accurate multi-reference wave function methodologies such as difference dedicated configuration interaction and the complete active space with second-order perturbation theory. © 2011 American Institute of Physics

Surface spin-electron acoustic waves in magnetically ordered metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru; Kuz'menkov, L. S., E-mail: lsk@phys.msu.ru

2016-05-09

Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma, we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area, the dispersion branches are located close to each other. In this area, there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuirmore » waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the spin-electron acoustic waves.« less

Angstrom-Resolution Magnetic Resonance Imaging of Single Molecules via Wave-Function Fingerprints of Nuclear Spins

NASA Astrophysics Data System (ADS)

Ma, Wen-Long; Liu, Ren-Bao

2016-08-01

Single-molecule sensitivity of nuclear magnetic resonance (NMR) and angstrom resolution of magnetic resonance imaging (MRI) are the highest challenges in magnetic microscopy. Recent development in dynamical-decoupling- (DD) enhanced diamond quantum sensing has enabled single-nucleus NMR and nanoscale NMR. Similar to conventional NMR and MRI, current DD-based quantum sensing utilizes the "frequency fingerprints" of target nuclear spins. The frequency fingerprints by their nature cannot resolve different nuclear spins that have the same noise frequency or differentiate different types of correlations in nuclear-spin clusters, which limit the resolution of single-molecule MRI. Here we show that this limitation can be overcome by using "wave-function fingerprints" of target nuclear spins, which is much more sensitive than the frequency fingerprints to the weak hyperfine interaction between the targets and a sensor under resonant DD control. We demonstrate a scheme of angstrom-resolution MRI that is capable of counting and individually localizing single nuclear spins of the same frequency and characterizing the correlations in nuclear-spin clusters. A nitrogen-vacancy-center spin sensor near a diamond surface, provided that the coherence time is improved by surface engineering in the near future, may be employed to determine with angstrom resolution the positions and conformation of single molecules that are isotope labeled. The scheme in this work offers an approach to breaking the resolution limit set by the "frequency gradients" in conventional MRI and to reaching the angstrom-scale resolution.

Influence of the local-spin-density correlation functional on the stability of bcc ferromagnetic iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, D.; Clougherty, D.P.; MacLaren, J.M.

1991-10-01

The influence of local-spin-dependent correlation effects on the predicted stable ground-state phase of iron is reexamined with use of general-potential linearized augmented-plane-wave calculations. Differences in the form of the Vosko-Wilk-Nusair (VWN) local-spin-density functional used in previous studies are noted, since in previous studies significant additional approximations were made with respect to those of Vosko, Wilk, and Nusan (Can. J. Phys. 58, 1200 (1980)) and of MacLaren, Clougherty, and Albers (Phys. Rev. B 42, 3205 (1990)). While the results of previous linear muffin-tin orbital calculations using the VWN functional predict a bcc ferromagnetic ground state, the present calculations show that themore » VWN spin-correlation effects fail to stabilize a bcc ground state. Considerable sensitivity to the form of the spin interpolation is found.« less

Spin-Hall nano-oscillator with oblique magnetization and Dzyaloshinskii-Moriya interaction as generator of skyrmions and nonreciprocal spin-waves

PubMed Central

Giordano, A.; Verba, R.; Zivieri, R.; Laudani, A.; Puliafito, V.; Gubbiotti, G.; Tomasello, R.; Siracusano, G.; Azzerboni, B.; Carpentieri, M.; Slavin, A.; Finocchio, G.

2016-01-01

Spin-Hall oscillators (SHO) are promising sources of spin-wave signals for magnonics applications, and can serve as building blocks for magnonic logic in ultralow power computation devices. Thin magnetic layers used as “free” layers in SHO are in contact with heavy metals having large spin-orbital interaction, and, therefore, could be subject to the spin-Hall effect (SHE) and the interfacial Dzyaloshinskii-Moriya interaction (i-DMI), which may lead to the nonreciprocity of the excited spin waves and other unusual effects. Here, we analytically and micromagnetically study magnetization dynamics excited in an SHO with oblique magnetization when the SHE and i-DMI act simultaneously. Our key results are: (i) excitation of nonreciprocal spin-waves propagating perpendicularly to the in-plane projection of the static magnetization; (ii) skyrmions generation by pure spin-current; (iii) excitation of a new spin-wave mode with a spiral spatial profile originating from a gyrotropic rotation of a dynamical skyrmion. These results demonstrate that SHOs can be used as generators of magnetic skyrmions and different types of propagating spin-waves for magnetic data storage and signal processing applications. PMID:27786261

Spin-Wave Chirality and Its Manifestations in Antiferromagnets

NASA Astrophysics Data System (ADS)

Proskurin, Igor; Stamps, Robert L.; Ovchinnikov, Alexander S.; Kishine, Jun-ichiro

2017-10-01

As first demonstrated by Tang and Cohen in chiral optics, the asymmetry in the rate of electromagnetic energy absorption between left and right enantiomers is determined by an optical chirality density. Here, we demonstrate that this effect can exist in magnetic spin systems. By constructing a formal analogy with electrodynamics, we show that in antiferromagnets with broken chiral symmetry, the asymmetry in local spin-wave energy absorption is proportional to a spin-wave chirality density, which is a direct counterpart of optical zilch. We propose that injection of a pure spin current into an antiferromagnet may serve as a chiral symmetry breaking mechanism, since its effect in the spin-wave approximation can be expressed in terms of additional Lifshitz invariants. We use linear response theory to show that the spin current induces a nonequilibrium spin-wave chirality density.

Spin Wave Theory in Two-Dimensional Coupled Antiferromagnets

NASA Astrophysics Data System (ADS)

Shimahara, Hiroshi

2018-04-01

We apply spin wave theory to two-dimensional coupled antiferromagnets. In particular, we primarily examine a system that consists of small spins coupled by a strong exchange interaction J1, large spins coupled by a weak exchange interaction J2, and an anisotropic exchange interaction J12 between the small and large spins. This system is an effective model of the organic antiferromagnet λ-(BETS)2FeCl4 in its insulating phase, in which intriguing magnetic phenomena have been observed, where the small and large spins correspond to π electrons and 3d spins, respectively. BETS stands for bis(ethylenedithio)tetraselenafulvalene. We obtain the antiferromagnetic transition temperature TN and the sublattice magnetizations m(T) and M(T) of the small and large spins, respectively, as functions of the temperature T. When T increases, m(T) is constant with a slight decrease below TN, even where M(T) decreases significantly. When J1 ≫ J12 and J2 = 0, an analytical expression for TN is derived. The estimated value of TN and the behaviors of m(T) and M(T) agree with the observations of λ-(BETS)2FeCl4.

Spectrum of spin waves in cold polarized gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreeva, T. L., E-mail: phdocandreeva@yandex.ru

2017-02-15

The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.

Field dependence of nonreciprocal magnons in chiral MnSi

NASA Astrophysics Data System (ADS)

Weber, T.; Waizner, J.; Tucker, G. S.; Georgii, R.; Kugler, M.; Bauer, A.; Pfleiderer, C.; Garst, M.; Böni, P.

2018-06-01

Spin waves in chiral magnetic materials are strongly influenced by the Dzyaloshinskii-Moriya interaction, resulting in intriguing phenomena like nonreciprocal magnon propagation and magnetochiral dichroism. Here, we study the nonreciprocal magnon spectrum of the archetypical chiral magnet MnSi and its evolution as a function of magnetic field covering the field-polarized and conical helix phase. Using inelastic neutron scattering, the magnon energies and their spectral weights are determined quantitatively after deconvolution with the instrumental resolution. In the field-polarized phase the imaginary part of the dynamical susceptibility χ''(ɛ ,q ) is shown to be asymmetric with respect to wave vectors q longitudinal to the applied magnetic field H , which is a hallmark of chiral magnetism. In the helimagnetic phase, χ''(ɛ ,q ) becomes increasingly symmetric with decreasing H due to the formation of helimagnon bands and the activation of additional spin-flip and non-spin-flip scattering channels. The neutron spectra are in excellent quantitative agreement with the low-energy theory of cubic chiral magnets with a single fitting parameter being the damping rate of spin waves.

Spin wave interference in YIG cross junction

DOE PAGES

Balinskiy, M.; Gutierrez, D.; Chiang, H.; ...

2017-01-17

This work is aimed at studying the interference between backward volume magnetostatic spin waves and magnetostatic surface spin waves in a magnetic cross junction. These two types of magnetostatic waves possess different dispersion with zero frequency overlap in infinite magnetic films. However, the interference may be observed in finite structures due to the effect magnetic shape anisotropy. We report experimental data on spin wave interference in a micrometer size Y 3Fe 2(FeO 4) 3 cross junction. There are four micro antennas fabricated at the edges of the cross arms. Two of these antennas located on the orthogonal arms are usedmore » for spin wave generation, and the other two antennas are used for the inductive voltage detection. The phase difference between the input signals is controlled by the phase shifter. Prominent spin wave interference is observed at the selected combination of operational frequency and bias magnetic field. The maximum On/Off ratio exceeds 30dB at room temperature. The obtained results are important for a variety of magnetic devices based on spin wave interference.« less

Spin-orbital quantum liquid on the honeycomb lattice

NASA Astrophysics Data System (ADS)

Corboz, Philippe

2013-03-01

The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. This approach can be seen as a two-dimensional generalization of matrix product states - the underlying ansatz of the density matrix renormalization group method. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-Néel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a good starting point to understand the recently discovered spin-orbital liquid behavior of Ba3CuSb2O9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms. We acknowledge the financial support from the Swiss National Science Foundation.

Nonlinear spin waves in magnetic thin films - foldover, dispersive shock waves, and spin pumping

NASA Astrophysics Data System (ADS)

Janantha, Pasdunkorale Arachchige Praveen

Three nonlinear phenomena of spin waves and the spin Seebeck effect in yttrium iron garnet (YIG)/Pt bi-layer structures are studied in this thesis and are reported in detail in Chapters 4-7. In the fourth chapter, the first observation of foldover effect of nonlinear eigenmodes in feedback ring systems is reported. The experiments made use of a system that consisted of a YIG thin film strip, which supported the propagation of forward volume spin waves, and a microwave amplifier, which amplified the signal from the output of the YIG strip and then fed it back to the input of the strip. The signal amplitude vs. frequency response in this ring system showed resonant peaks which resulted from ring eigenmodes. With an increase in the resonance amplitude, those resonant peaks evolved from symmetric peaks to asymmetric ones and then folded over to higher frequencies. The experimental observations were reproduced by theoretical calculations that took into account the nonlinearity-produced frequency shift of the traveling spin waves. The fifth chapter presents the first experimental observation of the formation of envelope dispersive shock wave (DSW) excitations from repulsive nonlinear spin waves. The experiments used a microwave step pulse to excite a spin-wave step pulse in a YIG thin film strip, in which the spin-wave amplitude increases rapidly. Under certain conditions, the spin-wave pulse evolved into a DSW excitation that consisted of a train of dark soliton-like dips with both the dip width and depth increasing from the front to the back and was terminated by a black soliton that had an almost zero intensity and a nearly 180° phase jump at its center. The sixth chapter reports on the spin pumping due to traveling spin waves. The experiment used a micron-thick YIG strip capped by a nanometer-thick Pt layer. The YIG film was biased by an in-plane magnetic field. The spin waves pumped spin currents into the Pt layer, and the later produced electrical voltages across the length of the Pt strip through the inverse spin Hall effect (ISHE). Several distinct pumping regimes were observed and were interpreted in the frame work of the nonlinear three-wave splitting processes of the spin waves. The seventh chapter presents the first experimental work on the roles of damping in the spin Seebeck effect (SSE). The experiments used YIG/Pt bi-layered structures where the YIG films exhibited very similar structural and static magnetic properties but very different damping. The data indicate that a decrease in the damping of the YIG film gives rise to an increase in the SSE coefficient, and this response shows quasi-linear behavior. The data also indicate that the SSE coefficient shows no notable dependences on the enhanced damping due to spin pumping.

Spin waves in full-polarized state of Dzyaloshinskii-Moriya helimagnets: Small-angle neutron scattering study

NASA Astrophysics Data System (ADS)

Grigoriev, S. V.; Sukhanov, A. S.; Altynbaev, E. V.; Siegfried, S.-A.; Heinemann, A.; Kizhe, P.; Maleyev, S. V.

2015-12-01

We develop the technique to study the spin-wave dynamics of the full-polarized state of the Dzyaloshinskii-Moriya helimagnets by polarized small-angle neutron scattering. We have experimentally proven that the spin-waves dispersion in this state has the anisotropic form. We show that the neutron scattering image displays a circle with a certain radius which is centered at the momentum transfer corresponding to the helix wave vector in helimagnetic phase ks, which is oriented along the applied magnetic field H . The radius of this circle is directly related to the spin-wave stiffness of this system. This scattering depends on the neutron polarization showing the one-handed nature of the spin waves in Dzyaloshinskii-Moriya helimagnets in the full-polarized phase. We show that the spin-wave stiffness A for MnSi helimagnet decreased twice as the temperature increases from zero to the critical temperature Tc.

Spin excitations in optimally P-doped BaFe 2 ( As 0.7 P 0.3 ) 2 superconductor

DOE PAGES

Hu, Ding; Yin, Zhiping; Zhang, Wenliang; ...

2016-09-02

We use inelastic neutron scattering to study temperature and energy dependence of spin excitations in optimally P-doped BaFe 2(As 0:7P 0:3) 2 superconductor (T c = 30 K) throughout the Brillouin zone. In the undoped state, spin waves and paramagnetic spin excitations of BaFe 2As 2 stem from antiferromagnetic (AF) ordering wave vector QAF = ( 1; 0) and peaks near zone boundary at ( 1; 1) around 180 meV. Replacing 30% As by smaller P to induce superconductivity, low-energy spin excitations of BaFe 2(As 0:7P 0:3) 2 form a resonance in the superconducting state and high-energy spin excitations nowmore » peaks around 220 meV near ( 1; 1). These results are consistent with calculations from a combined density functional theory and dynamical mean field theory, and suggest that the decreased average pnictogen height in BaFe 2(As 0:7P 0:3) 2 reduces the strength of electron correlations and increases the effective bandwidth of magnetic excitations.« less

Six Impossible Things: Fractional Charge From Laughlin's Wave Function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrivastava, Keshav N.

2010-12-23

The Laughlin's wave function is found to be the zero-energy ground state of a {delta}-function Hamiltonian. The finite negative value of the ground state energy which is 91 per cent of Wigner value, can be obtained only when Coulomb correlations are introduced. The Laughlin's wave function is of short range and it overlaps with that of the exact wave functions of small (number of electrons 2 or 5) systems. (i) It is impossible to obtain fractional charge from Laughlin's wave function. (ii) It is impossible to prove that the Laughlin's wave function gives the ground state of the Coulomb Hamiltonian.more » (iii) It is impossible to have particle-hole symmetry in the Laughlin's wave function. (iv) It is impossible to derive the value of m in the Laughlin's wave function. The value of m in {psi}{sub m} can not be proved to be 3 or 5. (v) It is impossible to prove that the Laughlin's state is incompressible because the compressible states are also likely. (vi) It is impossible for the Laughlin's wave function to have spin. This effort is directed to explain the experimental data of quantum Hall effect in GaAs/AlGaAs.« less

Second sound experiments in superfluid 3He-A1 phase in high magnetic fields

NASA Astrophysics Data System (ADS)

Bastea, Marina

The Asb1 phase of sp3He is the first observed magnetic superfluid, stable only in the presence of an external magnetic field. Due to the broken relative gauge and spin rotational symmetry, the two associated collective modes, the second sound and the longitudinal spin waves are expected to appear as a single mode which we call the spin-entropy wave. Our work is focused on consistently mapping the behavior of the spin-entropy wave in the superfluid Asb{1} phase of sp3He, under a wide range of experimental conditions. Our results address fundamental questions such as the identification of the order parameter symmetry in the superfluid states, the nature of the pairing state in the Asb1 phase and the superfluid density anisotropy. We extensively investigated the propagation of the spin-entropy wave as a function of temperature, magnetic field between 1 and 8 Tesla and liquid pressure up to 30 bar. Our results show that the superfluid density is directly proportional to the magnitude of the external field in the specified range, as predicted by theory. We discovered that in the vicinity of the transition to the Asb2 phase, over a fairly large temperature range, the spin-entropy wave suffers a divergent attenuation. The observed effects were suggested as evidence for the presence of a minority condensate population, "down spin" pairs, specific for the Asb2 phase, as predicted by Monien and Tewordt. We measured the superfluid density dependence on the pressure between 10 and 30 bar and directly related it to the fourth order coefficients of the Ginzburg-Landau free energy expansion. The pressure dependence of three of these coefficients and their strong coupling corrections was found to be consistent with the theoretical predictions of Sauls and Serene. Our results support the identification of the A phase as the Anderson-Brinkman-Morel axial state and provide an important consistency check for the phase diagram carried out by groups at USC and Cornell. We performed experiments in two different geometries (cylindrical and rectangular) for two relative orientations of the external field and the wave propagation direction, to measure the anisotropy of the superfluid density. We found that the spin-entropy wave propagation exhibits a non-linear character when the external field is perpendicular to the wave-vector. We modeled the textural configuration and the expected response of the system based on the free energy minimization criterion. The results of our theoretical model are in very good agreement with the experimental data.

Overcoming thermal noise in non-volatile spin wave logic

NASA Astrophysics Data System (ADS)

Dutta, Sourav; Nikonov, Dmitri; Manipatruni, Sasikanth; Young, Ian; Naeemi, Azad

Spin waves are propagating disturbances in magnetically ordered materials. To compete as a promising candidate for beyond-CMOS application, the all-magnon based computing system must undergo the essential steps of careful selection of materials and demonstrate robustness with respect to thermal noise/variability. Here, we identify suitable materials and investigate two viable options for translating the theoretical idea of phase-dependent switching of the spin wave detector to a practical realization of a thermally reliable magnonic device by - (a) using the built-in strain in the ME cell, arising from the lattice mismatch and/or thermal expansion coefficient mismatch between the film and the substrate, for compensation of the demagnetization, and (b) using an exchange-spring structure that exhibits a strong exchange-coupling between the ME cell and PMA SWB and provides a modification of the energy landscape of the ME cell magnet. A high switching success and error-free logic functionality can be ensured if the amplitude of the detected spin wave (< θ >) remains higher than a threshold value of around 6°C and the detected phase falls within the window from 280°C through 0 to 20°C or from 100°C to 200°C with a maximum allowable ϕ range of around 100°C.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cirac, J. Ignacio; Sierra, German; Instituto de Fisica Teorica, UAM-CSIC, Madrid

We generalize the matrix product states method using the chiral vertex operators of conformal field theory and apply it to study the ground states of the XXZ spin chain, the J{sub 1}-J{sub 2} model and random Heisenberg models. We compute the overlap with the exact wave functions, spin-spin correlators, and the Renyi entropy, showing that critical systems can be described by this method. For rotational invariant ansatzs we construct an inhomogenous extension of the Haldane-Shastry model with long-range exchange interactions.

Spin structure of electron subbands in (110)-grown quantum wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nestoklon, M. O.; Tarasenko, S. A.; Jancu, J.-M.

We present the theory of fine structure of electron states in symmetric and asymmetric zinc-blende-type quantum wells with the (110) crystallographic orientation. By combining the symmetry analysis, sp{sup 3}d{sup 5}s* tight-binding method, and envelope-function approach we obtain quantitative description of in-plane wave vector, well width and applied electric field dependencies of the zero-magnetic-field spin splitting of electron subbands and extract spin-orbit-coupling parameters.

Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu

A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed formore » excitation fluences higher than 100 mJ/cm{sup 2}.« less

Spin torque oscillator neuroanalog of von Neumann's microwave computer.

PubMed

Hoppensteadt, Frank

2015-10-01

Frequency and phase of neural activity play important roles in the behaving brain. The emerging understanding of these roles has been informed by the design of analog devices that have been important to neuroscience, among them the neuroanalog computer developed by O. Schmitt and A. Hodgkin in the 1930s. Later J. von Neumann, in a search for high performance computing using microwaves, invented a logic machine based on crystal diodes that can perform logic functions including binary arithmetic. Described here is an embodiment of his machine using nano-magnetics. Electrical currents through point contacts on a ferromagnetic thin film can create oscillations in the magnetization of the film. Under natural conditions these properties of a ferromagnetic thin film may be described by a nonlinear Schrödinger equation for the film's magnetization. Radiating solutions of this system are referred to as spin waves, and communication within the film may be by spin waves or by directed graphs of electrical connections. It is shown here how to formulate a STO logic machine, and by computer simulation how this machine can perform several computations simultaneously using multiplexing of inputs, that this system can evaluate iterated logic functions, and that spin waves may communicate frequency, phase and binary information. Neural tissue and the Schmitt-Hodgkin, von Neumann and STO devices share a common bifurcation structure, although these systems operate on vastly different space and time scales; namely, all may exhibit Andronov-Hopf bifurcations. This suggests that neural circuits may be capable of the computational functionality as described by von Neumann. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Acoustic parametric pumping of spin waves

NASA Astrophysics Data System (ADS)

Keshtgar, Hedyeh; Zareyan, Malek; Bauer, Gerrit E. W.

2014-11-01

Recent experiments demonstrated generation of spin currents by ultrasound. We can understand this acoustically induced spin pumping in terms of the coupling between magnetization and lattice waves. Here we study the parametric excitation of magnetization by longitudinal acoustic waves and calculate the acoustic threshold power. The induced magnetization dynamics can be detected by the spin pumping into an adjacent normal metal that displays the inverse spin Hall effect.

Multiconfiguration Pair-Density Functional Theory: A New Way To Treat Strongly Correlated Systems.

PubMed

Gagliardi, Laura; Truhlar, Donald G; Li Manni, Giovanni; Carlson, Rebecca K; Hoyer, Chad E; Bao, Junwei Lucas

2017-01-17

The electronic energy of a system provides the Born-Oppenheimer potential energy for internuclear motion and thus determines molecular structure and spectra, bond energies, conformational energies, reaction barrier heights, and vibrational frequencies. The development of more efficient and more accurate ways to calculate the electronic energy of systems with inherently multiconfigurational electronic structure is essential for many applications, including transition metal and actinide chemistry, systems with partially broken bonds, many transition states, and most electronically excited states. Inherently multiconfigurational systems are called strongly correlated systems or multireference systems, where the latter name refers to the need for using more than one ("multiple") configuration state function to provide a good zero-order reference wave function. This Account describes multiconfiguration pair-density functional theory (MC-PDFT), which was developed as a way to combine the advantages of wave function theory (WFT) and density functional theory (DFT) to provide a better treatment of strongly correlated systems. First we review background material: the widely used Kohn-Sham DFT (which uses only a single Slater determinant as reference wave function), multiconfiguration WFT methods that treat inherently multiconfigurational systems based on an active space, and previous attempts to combine multiconfiguration WFT with DFT. Then we review the formulation of MC-PDFT. It is a generalization of Kohn-Sham DFT in that the electron kinetic energy and classical electrostatic energy are calculated from a reference wave function, while the rest of the energy is obtained from a density functional. However, there are two main differences with respent to Kohn-Sham DFT: (i) The reference wave function is multiconfigurational rather than being a single Slater determinant. (ii) The density functional is a function of the total density and the on-top pair density rather than being a function of the spin-up and spin-down densities. In work carried out so far, the multiconfigurational wave function is a multiconfiguration self-consistent-field wave function. The new formulation has the advantage that the reference wave function has the correct spatial and spin symmetry and can describe bond dissociation (of both single and multiple bonds) and electronic excitations in a formally and physically correct way. We then review the formulation of density functionals in terms of the on-top pair density. Finally we review successful applications of the theory to bond energies and bond dissociation potential energy curves of main-group and transition metal bonds, to barrier heights (including pericyclic reactions), to proton affinities, to the hydrogen bond energy of water dimer, to ground- and excited-state charge transfer, to valence and Rydberg excitations of molecules, and to singlet-triplet splittings of radicals. We find that that MC-PDFT can give accurate results not only with complete-active-space multiconfiguration wave functions but also with generalized-active-space multiconfiguration wave functions, which are practical for larger numbers of active electrons and active orbitals than are complete-active-space wave functions. The separated-pair approximation, which is a special case of generalized active space self-consistent-field theory, is especially promising. MC-PDFT, because it requires much less computer time and storage than pure WFT methods, has the potential to open larger and more complex strongly correlated systems to accurate simulation.

Localized Defect Modes in a Two-Dimensional Array of Magnetic Nanodots

DTIC Science & Technology

2013-06-22

number of defects it is possible to obtain the information about the entire spin-wave spectrum of the array. Index Terms—Spin waves, magnonic crystal...multistability opens a way for the development of a novel type of artificial materials with tunable microwave properties – reconfigurable magnonic ...information about the entire spin-wave spectrum of the array. 15. SUBJECT TERMS Spin waves, magnonic crystal, magnetic dot, ferromagnetic resonance

Relativistic symmetries in the Rosen—Morse potential and tensor interaction using the Nikiforov—Uvarov method

NASA Astrophysics Data System (ADS)

Sameer, M. Ikhdair; Majid, Hamzavi

2013-04-01

Approximate analytical bound-state solutions of the Dirac particle in the fields of attractive and repulsive Rosen—Morse (RM) potentials including the Coulomb-like tensor (CLT) potential are obtained for arbitrary spin-orbit quantum number κ. The Pekeris approximation is used to deal with the spin-orbit coupling terms κ (κ± 1)r-2. In the presence of exact spin and pseudospin (p-spin) symmetries, the energy eigenvalues and the corresponding normalized two-component wave functions are found by using the parametric generalization of the Nikiforov—Uvarov (NU) method. The numerical results show that the CLT interaction removes degeneracies between the spin and p-spin state doublets.

Spin-wave wavelength down-conversion at thickness steps

NASA Astrophysics Data System (ADS)

Stigloher, Johannes; Taniguchi, Takuya; Madami, Marco; Decker, Martin; Körner, Helmut S.; Moriyama, Takahiro; Gubbiotti, Gianluca; Ono, Teruo; Back, Christian H.

2018-05-01

We report a systematic experimental study on the refraction and reflection of magnetostatic spin-waves at a thickness step between two Permalloy films of different thickness. The transmitted spin-waves for the transition from a thick film to a thin film have a higher wave vector compared to the incoming waves. Consequently, such systems may find use as passive wavelength transformers in magnonic networks. We investigate the spin-wave transmission behavior by studying the influence of the external magnetic field, incident angle, and thickness ratio of the films using time-resolved scanning Kerr microscopy and micro-focused Brillouin light scattering.

Expanding the Bethe/Gauge dictionary

NASA Astrophysics Data System (ADS)

Bullimore, Mathew; Kim, Hee-Cheol; Lukowski, Tomasz

2017-11-01

We expand the Bethe/Gauge dictionary between the XXX Heisenberg spin chain and 2d N = (2, 2) supersymmetric gauge theories to include aspects of the algebraic Bethe ansatz. We construct the wave functions of off-shell Bethe states as orbifold defects in the A-twisted supersymmetric gauge theory and study their correlation functions. We also present an alternative description of off-shell Bethe states as boundary conditions in an effective N = 4 supersymmetric quantum mechanics. Finally, we interpret spin chain R-matrices as correlation functions of Janus interfaces for mass parameters in the supersymmetric quantum mechanics.

Magnetic domain walls as reconfigurable spin-wave nano-channels

NASA Astrophysics Data System (ADS)

Wagner, Kai

Research efforts to utilize spin waves as information carriers for wave based logic in micro- and nano-structured ferromagnetic materials have increased tremendously over the recent years. However, finding efficient means of tailoring and downscaling guided spin-wave propagation in two dimensions, while maintaining energy efficiency and reconfigurability, still remains a delicate challenge. Here we target these challenges by spin-wave transport inside nanometer-scaled potential wells formed along magnetic domain walls. For this, we investigate the magnetization dynamics of a rectangular-like element in a Landau state exhibiting a so called 180° Néel wall along its center. By microwave antennae the rf-excitation is constricted to one end of the domain wall and the spin-wave intensities are recorded by means of Brillouin-Light Scattering microscopy revealing channeled transport. Additional micromagnetic simulations with pulsed as well as cw-excitation are performed to yield further insight into this class of modes. We find several spin-wave modes quantized along the width of the domain wall yet with well defined wave vectors along the wall, exhibiting positive dispersion. In a final step, we demonstrate the flexibility of these spin-wave nano-channels based on domain walls. In contrast to wave guides realised by fixed geometries, domain walls can be easily manipulated. Here we utilize small external fields to control its position with nanometer precision over a micrometer range, while still enabling transport. Domain walls thus, open the perspective for reprogrammable and yet non-volatile spin-wave waveguides of nanometer width. Financial support by the Deutsche Forschungsgemeinschaft within project SCHU2922/1-1 is gratefully acknowledged.

Spin-wave diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Jin; Yu, Weichao; Wu, Ruqian

A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound statesmore » in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. As a result, these findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.« less

Spin-wave diode

DOE PAGES

Lan, Jin; Yu, Weichao; Wu, Ruqian; ...

2015-12-28

A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound statesmore » in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. As a result, these findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.« less

An Exact Separation of the Spin-Free and Spin-Dependent Terms of the Dirac-Coulomb-Breit Hamiltonian

NASA Technical Reports Server (NTRS)

Dyall, Kenneth G.

1994-01-01

The Dirac Hamiltonian is transformed by extracting the operator (sigma x p)/2mc from the small component of the wave function and applying it to the operators of the original Hamiltonian. The resultant operators contain products of Paull matrices that can be rearranged to give spin-free and spin-dependent operators. These operators are the ones encountered in the Breit-Pauli Hamiltonian, as well as some of higher order in alpha(sup 2). However, since the transformation of the original Dirac Hamiltonian is exact, the new Hamiltonian can be used in variational calculations, with or without the spin-dependent terms. The new small component functions have the same symmetry properties as the large component. Use of only the spin-free terms of the new Hamiltonian permits the same factorization over spin variables as in nonrelativistic theory, and therefore all the post-Self-Consistent Field (SCF) machinery of nonrelativistic calculations can be applied. However, the single-particle functions are two-component orbitals having a large and small component, and the SCF methods must be modified accordingly. Numerical examples are presented, and comparisons are made with the spin-free second-order Douglas-Kroll transformed Hamiltonian of Hess.

Multi-directional emission and detection of spin waves propagating in yttrium iron garnet with wavelengths down to about 100 nm

NASA Astrophysics Data System (ADS)

Maendl, Stefan; Grundler, Dirk

2018-05-01

We performed broadband spin-wave spectroscopy on 200 nm thick yttrium iron garnet containing arrays of partially embedded magnetic nanodisks. Using integrated coplanar waveguides (CPWs), we studied the excitation and transmission of spin waves depending on the presence of nanomagnet arrays of different lateral extensions. By means of the grating coupler effect, we excited spin waves propagating in multiple lateral directions with wavelengths down to 111 nm. They exhibited group velocities of up to 1 km/s. Detection of such short-wavelength spin waves was possible only in symmetrically designed emitter/detector configurations, not with a bare CPW. We report spin waves propagating between grating couplers under oblique angles exhibiting a wave vector component parallel to the CPW. The effective propagation distance amounted to about 80 μm. Such transmission signals were not addressed before and substantiate the versatility of the grating coupler effect for implementing nanomagnonic circuits.

Quark fragmentation into spin-triplet S -wave quarkonium

DOE PAGES

Bodwin, Geoffrey T.; Chung, Hee Sok; Kim, U-Rae; ...

2015-04-08

We compute fragmentation functions for a quark to fragment to a quarkonium through an S-wave spin-triplet heavy quark-antiquark pair. We consider both color-singlet and color-octet heavy quark-antiquark (Q (Q) over bar) pairs. We give results for the case in which the fragmenting quark and the quark that is a constituent of the quarkonium have different flavors and for the case in which these quarks have the same flavors. Our results for the sum over all spin polarizations of the Q (Q) over bar pairs confirm previous results. Our results for longitudinally polarized Q (Q) over bar pairs agree with previousmore » calculations for the same flavor cases and correct an error in a previous calculation for the different-flavor case.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

DOE PAGES

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; ...

2017-05-24

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born–Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersionmore » of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.« less

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

NASA Astrophysics Data System (ADS)

Lemke, Henrik T.; Kjær, Kasper S.; Hartsock, Robert; van Driel, Tim B.; Chollet, Matthieu; Glownia, James M.; Song, Sanghoon; Zhu, Diling; Pace, Elisabetta; Matar, Samir F.; Nielsen, Martin M.; Benfatto, Maurizio; Gaffney, Kelly J.; Collet, Eric; Cammarata, Marco

2017-05-01

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings illustrate how modern time-resolved X-ray absorption spectroscopy can provide key information to unravel dynamic details of photo-functional molecules.

Generation of dark and bright spin wave envelope soliton trains through self-modulational instability in magnetic films.

PubMed

Wu, Mingzhong; Kalinikos, Boris A; Patton, Carl E

2004-10-08

The generation of dark spin wave envelope soliton trains from a continuous wave input signal due to spontaneous modulational instability has been observed for the first time. The dark soliton trains were formed from high dispersion dipole-exchange spin waves propagated in a thin yttrium iron garnet film with pinned surface spins at frequencies situated near the dipole gaps in the dipole-exchange spin wave spectrum. Dark and bright soliton trains were generated for one and the same film through placement of the input carrier frequency in regions of negative and positive dispersion, respectively. Two unreported effects in soliton dynamics, hysteresis and period doubling, were also observed.

A transverse separate-spin-evolution streaming instability

NASA Astrophysics Data System (ADS)

Iqbal, Z.; Andreev, Pavel A.; Murtaza, G.

2018-05-01

By using the separate spin evolution quantum hydrodynamical model, the instability of transverse mode due to electron streaming in a partially spin polarized magnetized degenerate plasma is studied. The electron spin polarization gives birth to a new spin-dependent wave (i.e., separate spin evolution streaming driven ordinary wave) in the real wave spectrum. It is shown that the spin polarization and streaming speed significantly affect the frequency of this new mode. Analyzing growth rate, it is found that the electron spin effects reduce the growth rate and shift the threshold of instability as well as its termination point towards higher values. Additionally, how the other parameters like electron streaming and Fermi pressure influence the growth rate is also investigated. Current study can help towards better understanding of the existence of new waves and streaming instability in the astrophysical plasmas.

Vertex functions at finite momentum: Application to antiferromagnetic quantum criticality

NASA Astrophysics Data System (ADS)

Wölfle, Peter; Abrahams, Elihu

2016-02-01

We analyze the three-point vertex function that describes the coupling of fermionic particle-hole pairs in a metal to spin or charge fluctuations at nonzero momentum. We consider Ward identities, which connect two-particle vertex functions to the self-energy, in the framework of a Hubbard model. These are derived using conservation laws following from local symmetries. The generators considered are the spin density and particle density. It is shown that at certain antiferromagnetic critical points, where the quasiparticle effective mass is diverging, the vertex function describing the coupling of particle-hole pairs to the spin density Fourier component at the antiferromagnetic wave vector is also divergent. Then we give an explicit calculation of the irreducible vertex function for the case of three-dimensional antiferromagnetic fluctuations, and show that it is proportional to the diverging quasiparticle effective mass.

Spin-wave interference in microscopic permalloy tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balhorn, Felix; Nagrodzki, Lukas; Mendach, Stefan

2013-06-03

We present permalloy coated needles which act as spin-wave resonators. The permalloy coated needles were investigated using microwave absorption spectroscopy. Thereby, we found up to three resonant modes which correspond to constructively interfering azimuthal spin waves. The resonant modes are well reproduced in calculations based on an analytical model for the spin-wave dispersion employing periodic boundary conditions. The dependence of the resonance frequencies on the needles' radii and the external magnetic field is demonstrated experimentally.

Spin and charge thermopower effects in the ferromagnetic graphene junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahedi, Javad, E-mail: javahedi@gmail.com; Center for Theoretical Physics of Complex Systems, Institute for Basic Science; Barimani, Fattaneh

2016-08-28

Using wave function matching approach and employing the Landauer-Buttiker formula, a ferromagnetic graphene junction with temperature gradient across the system is studied. We calculate the thermally induced charge and spin current as well as the thermoelectric voltage (Seebeck effect) in the linear and nonlinear regimes. Our calculation revealed that due to the electron-hole symmetry, the charge Seebeck coefficient is, for an undoped magnetic graphene, an odd function of chemical potential while the spin Seebeck coefficient is an even function regardless of the temperature gradient and junction length. We have also found with an accurate tuning external parameter, namely, the exchangemore » filed and gate voltage, the temperature gradient across the junction drives a pure spin current without accompanying the charge current. Another important characteristic of thermoelectric transport, thermally induced current in the nonlinear regime, is examined. It would be our main finding that with increasing thermal gradient applied to the junction the spin and charge thermovoltages decrease and even become zero for non zero temperature bias.« less

Parallel pumping for magnon spintronics: Amplification and manipulation of magnon spin currents on the micron-scale

NASA Astrophysics Data System (ADS)

Brächer, T.; Pirro, P.; Hillebrands, B.

2017-06-01

Magnonics and magnon spintronics aim at the utilization of spin waves and magnons, their quanta, for the construction of wave-based logic networks via the generation of pure all-magnon spin currents and their interfacing with electric charge transport. The promise of efficient parallel data processing and low power consumption renders this field one of the most promising research areas in spintronics. In this context, the process of parallel parametric amplification, i.e., the conversion of microwave photons into magnons at one half of the microwave frequency, has proven to be a versatile tool to excite and to manipulate spin waves. Its beneficial and unique properties such as frequency and mode-selectivity, the possibility to excite spin waves in a wide wavevector range and the creation of phase-correlated wave pairs, have enabled the achievement of important milestones like the magnon Bose-Einstein condensation and the cloning and trapping of spin-wave packets. Parallel parametric amplification, which allows for the selective amplification of magnons while conserving their phase is, thus, one of the key methods of spin-wave generation and amplification. The application of parallel parametric amplification to CMOS-compatible micro- and nano-structures is an important step towards the realization of magnonic networks. This is motivated not only by the fact that amplifiers are an important tool for the construction of any extended logic network but also by the unique properties of parallel parametric amplification. In particular, the creation of phase-correlated wave pairs allows for rewarding alternative logic operations such as a phase-dependent amplification of the incident waves. Recently, the successful application of parallel parametric amplification to metallic microstructures has been reported which constitutes an important milestone for the application of magnonics in practical devices. It has been demonstrated that parametric amplification provides an excellent tool to generate and to amplify spin waves in these systems in a wide wavevector range. In particular, the amplification greatly benefits from the discreteness of the spin-wave spectra since the size of the microstructures is comparable to the spin-wave wavelength. This opens up new, interesting routes of spin-wave amplification and manipulation. In this review, we will give an overview over the recent developments and achievements in this field.

Generation of propagating backward volume spin waves by phase-sensitive mode conversion in two-dimensional microstructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braecher, T.; Sebastian, T.; Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, D-67663 Kaiserslautern

2013-04-01

We present the generation of propagating backward volume (BV) spin waves in a T shaped Ni{sub 81}Fe{sub 19} microstructure. These waves are created from counterpropagating Damon Eshbach spin waves, which are excited using microstrip antennas. By employing Brillouin light scattering microscopy, we show how the phase relation between the counterpropagating waves determines the mode generated in the center of the structure, and prove its propagation inside the longitudinally magnetized part of the T shaped microstructure. This gives access to the effective generation of backward volume spin waves with full control over the generated transverse mode.

Direct observation of isolated Damon-Eshbach and backward volume spin-wave packets in ferromagnetic microstripes

PubMed Central

Wessels, Philipp; Vogel, Andreas; Tödt, Jan-Niklas; Wieland, Marek; Meier, Guido; Drescher, Markus

2016-01-01

The analysis of isolated spin-wave packets is crucial for the understanding of magnetic transport phenomena and is particularly interesting for applications in spintronic and magnonic devices, where isolated spin-wave packets implement an information processing scheme with negligible residual heat loss. We have captured microscale magnetization dynamics of single spin-wave packets in metallic ferromagnets in space and time. Using an optically driven high-current picosecond pulse source in combination with time-resolved scanning Kerr microscopy probed by femtosecond laser pulses, we demonstrate phase-sensitive real-space observation of spin-wave packets in confined permalloy (Ni80Fe20) microstripes. Impulsive excitation permits extraction of the dynamical parameters, i.e. phase- and group velocities, frequencies and wave vectors. In addition to well-established Damon-Eshbach modes our study reveals waves with counterpropagating group- and phase-velocities. Such unusual spin-wave motion is expected for backward volume modes where the phase fronts approach the excitation volume rather than emerging out of it due to the negative slope of the dispersion relation. These modes are difficult to excite and observe directly but feature analogies to negative refractive index materials, thus enabling model studies of wave propagation inside metamaterials. PMID:26906113

Spin-wave energy dispersion of a frustrated spin-½ Heisenberg antiferromagnet on a stacked square lattice.

PubMed

Majumdar, Kingshuk

2011-03-23

The effects of interlayer coupling and spatial anisotropy on the spin-wave excitation spectra of a three-dimensional spatially anisotropic, frustrated spin-½ Heisenberg antiferromagnet (HAFM) are investigated for the two ordered phases using second-order spin-wave expansion. We show that the second-order corrections to the spin-wave energies are significant and find that the energy spectra of the three-dimensional HAFM have similar qualitative features to the energy spectra of the two-dimensional HAFM on a square lattice. We also discuss the features that can provide experimental measures for the strength of the interlayer coupling, spatial anisotropy parameter, and magnetic frustration.

Critical anisotropies of a geometrically frustrated triangular-lattice antiferromagnet

NASA Astrophysics Data System (ADS)

Swanson, M.; Haraldsen, J. T.; Fishman, R. S.

2009-05-01

This work examines the critical anisotropy required for the local stability of the collinear ground states of a geometrically frustrated triangular-lattice antiferromagnet (TLA). Using a Holstein-Primakoff expansion, we calculate the spin-wave frequencies for the one-, two-, three-, four-, and eight-sublattice (SL) ground states of a TLA with up to third neighbor interactions. Local stability requires that all spin-wave frequencies are real and positive. The two-, four-, and eight-SL phases break up into several regions where the critical anisotropy is a different function of the exchange parameters. We find that the critical anisotropy is a continuous function everywhere except across the two-SL/three-SL and three-SL/four-SL phase boundaries, where the three-SL phase has the higher critical anisotropy.

Critical Anisotropies of a Geometrically-Frustrated Triangular-Lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanson, Mason R; Haraldsen, Jason T; Fishman, Randy Scott

2009-01-01

This work examines the critical anisotropy required for the local stability of the collinear ground states of a geometrically-frustrated triangular-lattice antiferromagnet (TLA). Using a Holstein-Primakoff expansion, we calculate the spin-wave frequencies for the 1, 2, 3, 4, and 8-sublattice (SL) ground states of a TLA with up to third neighbor interactions. Local stability requires that all spin-wave frequencies are real and positive. The 2, 4, and 8-SL phases break up into several regions where the critical anisotropy is a different function of the exchange parameters. We find that the critical anisotropy is a continuous function everywhere except across the 2-SL/3-SLmore » and 3-SL/4-SL phase boundaries, where the 3-SL phase has the higher critical anisotropy.« less

Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet.

PubMed

Korkusinski, M; Hawrylak, P; Liu, H W; Hirayama, Y

2017-03-06

The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means.

Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet

PubMed Central

Korkusinski, M.; Hawrylak, P.; Liu, H. W.; Hirayama, Y.

2017-01-01

The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means. PMID:28262758

Strong excitation of surface and bulk spin waves in yttrium iron garnet placed in a split ring resonator

NASA Astrophysics Data System (ADS)

Tay, Z. J.; Soh, W. T.; Ong, C. K.

2018-02-01

This paper presents an experimental study of the inverse spin Hall effect (ISHE) in a bilayer consisting of a yttrium iron garnet (YIG) and platinum (Pt) loaded on a metamaterial split ring resonator (SRR). The system is excited by a microstrip feed line which generates both surface and bulk spin waves in the YIG. The spin waves subsequently undergo spin pumping from the YIG film to an adjacent Pt layer, and is converted into a charge current via the ISHE. It is found that the presence of the SRR causes a significant enhancement of the mangetic field near the resonance frequency of the SRR, resulting in a significant increase in the ISHE signal. Furthermore, the type of spin wave generated in the system can be controlled by changing the external applied magnetic field angle (θH ). When the external applied magnetic field is near parallel to the microstrip line (θH = 0 ), magnetostatic surface spin waves are predominantly excited. On the other hand, when the external applied magnetic field is perpendicular to the microstrip line (θH = π/2 ), backward volume magnetostatic spin waves are predominantly excited. Hence, it can be seen that the SRR structure is a promising method of achieving spin-charge conversion, which has many advantages over a coaxial probe.

Excitation of short-wavelength spin waves in magnonic waveguides

NASA Astrophysics Data System (ADS)

Demidov, V. E.; Kostylev, M. P.; Rott, K.; Münchenberger, J.; Reiss, G.; Demokritov, S. O.

2011-08-01

By using phase-resolved micro-focus Brillouin light scattering spectroscopy, we demonstrate experimentally a phenomenon of wavelength conversion of spin waves propagating in tapered Permalloy waveguides. We show that this phenomenon enables efficient excitation of spin waves with sub-micrometer wavelengths being much smaller than the width of the microstrip antenna used for the excitation. The proposed excitation mechanism removes restrictions on the spin-wave wavelength imposed by the size of the antenna and enables improvement of performances of integrated magnonic devices.

Theory of spin and lattice wave dynamics excited by focused laser pulses

NASA Astrophysics Data System (ADS)

Shen, Ka; Bauer, Gerrit E. W.

2018-06-01

We develop a theory of spin wave dynamics excited by ultrafast focused laser pulses in a magnetic film. We take into account both the volume and surface spin wave modes in the presence of applied, dipolar and magnetic anisotropy fields and include the dependence on laser spot exposure size and magnetic damping. We show that the sound waves generated by local heating by an ultrafast focused laser pulse can excite a wide spectrum of spin waves (on top of a dominant magnon–phonon contribution). Good agreement with recent experiments supports the validity of the model.

Dynamic generation of spin-wave currents in hybrid structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyapilin, I. I.; Okorokov, M. S., E-mail: Okorokovmike@gmail.com

2016-11-15

Spin transport through the interface in a semiconductor/ferromagnetic insulator hybrid structure is studied by the nonequilibrium statistical operator method under conditions of the spin Seebeck effect. The effective parameter approach in which each examined subsystem (conduction electrons, magnons, phonons) is characterized by its specific effective temperature is considered. The effect of the resonant (electric dipole) excitation of the spin electronic subsystem of conduction electrons on spin-wave current excitation in a ferromagnetic insulator is considered. The macroscopic equations describing the spin-wave current caused by both resonant excitation of the spin system of conduction electrons and the presence of a nonuniform temperaturemore » field in the ferromagnetic insulator are derived taking into account both the resonance-diffusion propagation of magnons and their relaxation processes. It is shown that spin-wave current excitation is also of resonant nature under the given conditions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yizhou, E-mail: yliu062@ucr.edu; Yin, Gen; Lake, Roger K., E-mail: rlake@ece.ucr.edu

Single skyrmion creation and annihilation by spin waves in a crossbar geometry are theoretically analyzed. A critical spin-wave frequency is required both for the creation and the annihilation of a skyrmion. The minimum frequencies for creation and annihilation are similar, but the optimum frequency for creation is below the critical frequency for skyrmion annihilation. If a skyrmion already exists in the cross bar region, a spin wave below the critical frequency causes the skyrmion to circulate within the central region. A heat assisted creation process reduces the spin-wave frequency and amplitude required for creating a skyrmion. The effective field resultingmore » from the Dzyaloshinskii-Moriya interaction and the emergent field of the skyrmion acting on the spin wave drive the creation and annihilation processes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papp, A., E-mail: apapp@nd.edu; Pázmány Péter Catholic University, Faculty of Information Technology, Budapest 1088; Porod, W., E-mail: porod@nd.edu

We study coupled ferromagnetic layers, which could facilitate low loss, sub 100 nm wavelength spin-wave propagation and manipulation. One of the layers is a low-loss garnet film (such as yttrium iron garnet (YIG)) that enables long-distance, coherent spin-wave propagation. The other layer is made of metal-based (Permalloy, Co, and CoFe) magnetoelectronic structures that can be used to generate, manipulate, and detect the spin waves. Using micromagnetic simulations, we analyze the interactions between the spin waves in the YIG and the metallic nanomagnet structures and demonstrate the components of a scalable spin-wave based signal processing device. We argue that such hybrid-metallic ferromagnetmore » structures can be the basis of potentially high-performance, ultra low-power computing devices.« less

Coriolis effect in optics: unified geometric phase and spin-Hall effect.

PubMed

Bliokh, Konstantin Y; Gorodetski, Yuri; Kleiner, Vladimir; Hasman, Erez

2008-07-18

We examine the spin-orbit coupling effects that appear when a wave carrying intrinsic angular momentum interacts with a medium. The Berry phase is shown to be a manifestation of the Coriolis effect in a noninertial reference frame attached to the wave. In the most general case, when both the direction of propagation and the state of the wave are varied, the phase is given by a simple expression that unifies the spin redirection Berry phase and the Pancharatnam-Berry phase. The theory is supported by the experiment demonstrating the spin-orbit coupling of electromagnetic waves via a surface plasmon nanostructure. The measurements verify the unified geometric phase, demonstrated by the observed polarization-dependent shift (spin-Hall effect) of the waves.

Antiferromagnetic Spin Wave Field-Effect Transistor

DOE PAGES

Cheng, Ran; Daniels, Matthew W.; Zhu, Jian-Gang; ...

2016-04-06

In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. In conclusion, our findings open up the exciting possibilitymore » of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale.« less

Phase control of spin waves based on a magnetic defect in a one-dimensional magnonic crystal

NASA Astrophysics Data System (ADS)

Baumgaertl, Korbinian; Watanabe, Sho; Grundler, Dirk

2018-04-01

Magnonic crystals are interesting for spin-wave based data processing. We investigate one-dimensional magnonic crystals (1D MCs) consisting of bistable Co 20 Fe 60 B 20 nanostripes separated by 75 nm wide air gaps. By adjusting the magnetic history, we program a single stripe of opposed magnetization in an otherwise saturated 1D MC. Its influence on propagating spin waves is studied via broadband microwave spectroscopy. Depending on an in-plane bias magnetic field, we observe spin wave phase shifts of up to almost π and field-controlled attenuation attributed to the reversed nanostripe. Our findings are of importance for magnetologics, where the control of spin wave phases is essential.

Low temperature nano-spin filtering using a diluted magnetic semiconductor core-shell quantum dot

NASA Astrophysics Data System (ADS)

Chattopadhyay, Saikat; Sen, Pratima; Andrews, Joshep Thomas; Sen, Pranay Kumar

2014-07-01

The spin polarized electron transport properties and spin polarized tunneling current have been investigated analytically in a diluted magnetic semiconductor core-shell quantum dot in the presence of applied electric and magnetic fields. Assuming the electron wave function to satisfy WKB approximation, the electron energy eigenvalues have been calculated. The spin polarized tunneling current and the spin dependent tunneling coefficient are obtained by taking into account the exchange interaction and Zeeman splitting. Numerical estimates made for a specific diluted magnetic semiconductor, viz., Zn1-xMnxSe/ZnS core-shell quantum dot establishes the possibility of a nano-spin filter for a particular biasing voltage and applied magnetic field. Influence of applied voltage on spin polarized electron transport has been investigated in a CSQD.

Collective Yu-Shiba-Rusinov states in magnetic clusters at superconducting surfaces

NASA Astrophysics Data System (ADS)

Körber, Simon; Trauzettel, Björn; Kashuba, Oleksiy

2018-05-01

We study the properties of collective Yu-Shiba-Rusinov (YSR) states generated by multiple magnetic adatoms (clusters) placed on the surface of a superconductor. For magnetic clusters with equal distances between their constituents, we demonstrate the formation of effectively spin-unpolarized YSR states with subgap energies independent of the spin configuration of the magnetic impurities. We solve the problem analytically for arbitrary spin structure and analyze both spin-polarized (dispersive energy levels) and spin-unpolarized (pinned energy levels) solutions. While the energies of the spin-polarized solutions can be characterized solely by the net magnetic moment of the cluster, the wave functions of the spin-unpolarized solutions effectively decouple from it. This decoupling makes them stable against thermal fluctuation and detectable in scanning tunneling microscopy experiments.

Classification of trivial spin-1 tensor network states on a square lattice

NASA Astrophysics Data System (ADS)

Lee, Hyunyong; Han, Jung Hoon

2016-09-01

Classification of possible quantum spin liquid (QSL) states of interacting spin-1/2's in two dimensions has been a fascinating topic of condensed matter for decades, resulting in enormous progress in our understanding of low-dimensional quantum matter. By contrast, relatively little work exists on the identification, let alone classification, of QSL phases for spin-1 systems in dimensions higher than one. Employing the powerful ideas of tensor network theory and its classification, we develop general methods for writing QSL wave functions of spin-1 respecting all the lattice symmetries, spin rotation, and time reversal with trivial gauge structure on the square lattice. We find 25 distinct classes characterized by five binary quantum numbers. Several explicit constructions of such wave functions are given for bond dimensions D ranging from two to four, along with thorough numerical analyses to identify their physical characters. Both gapless and gapped states are found. The topological entanglement entropy of the gapped states is close to zero, indicative of topologically trivial states. In D =4 , several different tensors can be linearly combined to produce a family of states within the same symmetry class. A rich "phase diagram" can be worked out among the phases of these tensors, as well as the phase transitions among them. Among the states we identified in this putative phase diagram is the plaquette-ordered phase, gapped resonating valence bond phase, and a critical phase. A continuous transition separates the plaquette-ordered phase from the resonating valence bond phase.

Metastable Bound States of Two-Dimensional Magnetoexcitons in the Lowest Landau Levels Approximation

NASA Astrophysics Data System (ADS)

Moskalenko, S. A.; Khadzhi, P. I.; Podlesny, I. V.; Dumanov, E. V.; Liberman, M. A.; Zubac, I. A.

2017-12-01

The possible existence of the two-dimensional bimagnetoexcitons and metastable bound states formed by two magnetoexcitons with opposite in-plane wave vectors k and -k has been studied. Magnetoexcitons taking part in the formation of molecules look as two electric dipoles with the arms oriented in-plane perpendicular to the respective wave vectors and with the length of the arms d=k(l_0)^2, where l_0 is the magnetic length. Two antiparallel dipoles moving with equal, yet antiparallel, wave vectors have the possibility of moving with equal probability in any direction of the plane, which is determined by the trial wave function of relative motion φ_n(|k|), depending on modulus k. The magnetoexcitons are composed of electrons and holes situated on the lowest Landau levels with the cyclotron energies greater than the binding energy of the 2D Wannier-Mott exciton. The description has been made in Landau gauge. The spin states of two electrons have been chosen in the form of antisymmetric or symmetric combinations with parameter η=+/-1. The effective spins of two heavy holes have been combined in the same resultant spinor states as the spin of the electrons. Because the projections of the both spinor states with η=+/-1 are equal to zero, the influence of the Zeeman splitting effect vanishes. In the case of trial wave function, the maximal density of the magnetoexcitons in the momentum space is concentrated on the in-plane ring. In the approximation of the lowest Landau levels, when the influence of the excited Landau levels is neglected, stable bound states of bimagnetoexcitons do not exist for both spin orientations. Instead, in the case of α=0.5 and η=1, a deep metastable bound state with the activation barrier comparable with two magnetoexciton ionization potentials 2I_l has been revealed. In the case of η=-1 and α=3.4, only a shallow metastable bound state can appear.

The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fertitta, Edoardo; Paulus, Beate; El Khatib, Muammar

2015-12-28

The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum ismore » associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection S{sub z} has been derived.« less

Quasiclassical description of a superconductor with a spin density wave

NASA Astrophysics Data System (ADS)

Moor, A.; Volkov, A. F.; Efetov, K. B.

2011-04-01

We derive equations for the quasiclassical Green’s functions ǧ within a simple model of a two-band superconductor with a spin density wave (SDW). The elements of the matrix ǧ are the retarded, advanced, and Keldysh functions, each of which is an 8×8 matrix in the Gor’kov-Nambu, the spin, and the band space. In equilibrium, these equations are a generalization of the Eilenberger equation. On the basis of the derived equations, we analyze the Knight shift, the proximity, and the dc Josephson effects in the superconductors under consideration. The Knight shift is shown to depend on the orientation of the external magnetic field with respect to the direction of the vector of the magnetization of the SDW. The proximity effect is analyzed for an interface between a superconductor with the SDW and a normal metal. The function describing both superconducting and magnetic correlations is shown to penetrate the normal metal or a metal with the SDW due to the proximity effect. The dc Josephson current in an SSDW/N/SSDW junction is also calculated as a function of the phase difference φ. It is shown that in our model, the Josephson current does not depend on the mutual orientation of the magnetic moments in the superconductors SSDW and is proportional to sinφ. The dissipationless spin current jsp depends on the angle α between the magnetization vectors in the same way (jsp~sinα) and is not zero above the superconducting transition temperature.

FAST TRACK COMMUNICATION: Spin waves in the (0, π) and (0, π, π) ordered SDW states of the t-t' Hubbard model: application to doped iron pnictides

NASA Astrophysics Data System (ADS)

Raghuvanshi, Nimisha; Singh, Avinash

2010-10-01

Spin waves in the (0, π) and (0, π, π) ordered spin-density-wave (SDW) states of the t-t' Hubbard model are investigated at finite doping. In the presence of small t', these composite ferro-antiferromagnetic (F-AF) states are found to be strongly stabilized at finite hole doping due to enhanced carrier-induced ferromagnetic spin couplings as in metallic ferromagnets. Anisotropic spin-wave velocities, a spin-wave energy scale of around 200 meV, reduced magnetic moment and rapid suppression of magnetic order with electron doping x (corresponding to F substitution of O atoms in LaO1 - xFxFeAs or Ni substitution of Fe atoms in BaFe2 - xNixAs2) obtained in this model are in agreement with observed magnetic properties of doped iron pnictides.

Spin wave spectra in perpendicularly magnetized permalloy rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, X.; Ding, J.; Adeyeye, A. O., E-mail: eleaao@nus.edu.sg

2015-03-16

The dynamic behavior of perpendicularly magnetized permalloy circular rings is systematically investigated as a function of film thickness using broadband field modulated ferromagnetic resonance spectroscopy. We observed the splitting of one spin wave mode into a family of dense resonance peaks for the rings, which is markedly different from the single mode observed for continuous films of the same thickness. As the excitation frequency is increased, the mode family observed for the rings gradually converges into one mode. With the increase in the film thickness, a sparser spectrum of modes is observed. Our experimental results are in qualitative agreement withmore » the dynamic micromagnetic simulations.« less

Variational model for one-dimensional quantum magnets

NASA Astrophysics Data System (ADS)

Kudasov, Yu. B.; Kozabaranov, R. V.

2018-04-01

A new variational technique for investigation of the ground state and correlation functions in 1D quantum magnets is proposed. A spin Hamiltonian is reduced to a fermionic representation by the Jordan-Wigner transformation. The ground state is described by a new non-local trial wave function, and the total energy is calculated in an analytic form as a function of two variational parameters. This approach is demonstrated with an example of the XXZ-chain of spin-1/2 under a staggered magnetic field. Generalizations and applications of the variational technique for low-dimensional magnetic systems are discussed.

Voltage-Controlled Reconfigurable Spin-Wave Nanochannels and Logic Devices

NASA Astrophysics Data System (ADS)

Rana, Bivas; Otani, YoshiChika

2018-01-01

Propagating spin waves (SWs) promise to be a potential information carrier in future spintronics devices with lower power consumption. Here, we propose reconfigurable nanochannels (NCs) generated by voltage-controlled magnetic anisotropy (VCMA) in an ultrathin ferromagnetic waveguide for SW propagation. Numerical micromagnetic simulations are performed to demonstrate the confinement of magnetostatic forward volumelike spin waves in NCs by VCMA. We demonstrate that the NCs, with a width down to a few tens of a nanometer, can be configured either into a straight or curved structure on an extended SW waveguide. The key advantage is that either a single NC or any combination of a number of NCs can be easily configured by VCMA for simultaneous propagation of SWs either with the same or different wave vectors according to our needs. Furthermore, we demonstrate the logic operation of a voltage-controlled magnonic xnor and universal nand gate and propose a voltage-controlled reconfigurable SW switch for the development of a multiplexer and demultiplexer. We find that the NCs and logic devices can even be functioning in the absence of the external-bias magnetic field. These results are a step towards the development of all-voltage-controlled magnonic devices with an ultralow power consumption.

Clean Os(0001) electronic surface states: A first-principle fully relativistic investigation

NASA Astrophysics Data System (ADS)

Urru, Andrea; Dal Corso, Andrea

2018-05-01

We analyze the electronic structure of the Os(0001) surface by means of first-principle calculations based on Fully Relativistic (FR) Density Functional Theory (DFT) and a Projector Augmented-Wave (PAW) approach. We investigate surface states and resonances analyzing their spin-orbit induced energy splitting and their spin polarization. The results are compared with previously studied surfaces Ir(111), Pt(111), and Au(111). We do not find any surface state in the gap similar to the L-gap of the (111) fcc surfaces, but find Rashba split resonances that cross the Fermi level and, as in the recently studied Ir(111) surface, have a characteristic downward dispersion. Moreover, for some selected surface states we study the spin polarization with respect to k∥, the wave-vector parallel to the surface. In some cases, such as the Rashba split resonances, the spin polarization shows a smooth behavior with slow rotations, in others the rotation is faster, due to mixing and anti-crossing of the states.

Two-magnon excitations in resonant inelastic x-ray scattering studied within spin density wave formalism

NASA Astrophysics Data System (ADS)

Nomura, Takuji

2017-10-01

We study two-magnon excitations in resonant inelastic x-ray scattering (RIXS) at the transition-metal K edge. Instead of working with effective Heisenberg spin models, we work with a Hubbard-type model (d -p model) for a typical insulating cuprate La2CuO4 . For the antiferromagnetic ground state within the spin density wave (SDW) mean-field formalism, we calculate the dynamical correlation function within the random-phase approximation (RPA), and then obtain two-magnon excitation spectra by calculating the convolution of it. Coupling between the K -shell hole and the magnons in the intermediate state is calculated by means of diagrammatic perturbation expansion in the Coulomb interaction. The calculated momentum dependence of RIXS spectra agrees well with that of experiments. A notable difference from previous calculations based on the Heisenberg spin models is that RIXS spectra have a large two-magnon weight near the zone center, which may be confirmed by further careful high-resolution experiments.

Persistent Spin Current in a Hard-Wall Confining Quantum Wire with Weak Dresselhaus Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Fu, Xi; Zhou, Guang-Hui

2009-02-01

We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density js,xiT and js,yiT (i = x, y, z). We find that the elements jTs,xx and jTs,yy have a antisymmetrical relation and the element jTs,yz has the same amount level as js,xxT and js,yyT. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.

USSR and Eastern Europe Scientific Abstracts- Physics - Number 45

DTIC Science & Technology

1978-10-02

compound, a function of the angle between the electrical vector of the ’ light wave and the optical c-axis of the crystal. Heterodiodes have first...of naturally radioactive U, Th and K in a 1-liter sample. USSR A VECTOR MESON IN A QUANTUM ELECTROMAGNETIC FIELD Moscow TEORETICHESKAYA I...arbitrary spin in a classical plane electromagnetic field are used to find the exact wave function of a vector meson in the quantum field of a linearly

Microwave excitation of spin wave beams in thin ferromagnetic films

PubMed Central

Gruszecki, P.; Kasprzak, M.; Serebryannikov, A. E.; Krawczyk, M.; Śmigaj, W.

2016-01-01

An inherent element of research and applications in photonics is a beam of light. In magnonics, which is the magnetic counterpart of photonics, where spin waves are used instead of electromagnetic waves to transmit and process information, the lack of a beam source limits exploration. Here, we present an approach enabling generation of narrow spin wave beams in thin homogeneous nanosized ferromagnetic films by microwave current. We show that the desired beam-type behavior can be achieved with the aid of a properly designed coplanar waveguide transducer generating a nonuniform microwave magnetic field. We test this idea using micromagnetic simulations, confirming numerically that the resulting spin wave beams propagate over distances of several micrometers. The proposed approach requires neither inhomogeneity of the ferromagnetic film nor nonuniformity of the biasing magnetic field. It can be generalized to different magnetization configurations and yield multiple spin wave beams of different width at the same frequency. PMID:26971711

Dynamics of magnetization in ferromagnet with spin-transfer torque

NASA Astrophysics Data System (ADS)

Li, Zai-Dong; He, Peng-Bin; Liu, Wu-Ming

2014-11-01

We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.

Generalized valence bond description of the ground states (X(1)Σg(+)) of homonuclear pnictogen diatomic molecules: N2, P2, and As2.

PubMed

Xu, Lu T; Dunning, Thom H

2015-06-09

The ground state, X1Σg+, of N2 is a textbook example of a molecule with a triple bond consisting of one σ and two π bonds. This assignment, which is usually rationalized using molecular orbital (MO) theory, implicitly assumes that the spins of the three pairs of electrons involved in the bonds are singlet-coupled (perfect pairing). However, for a six-electron singlet state, there are five distinct ways to couple the electron spins. The generalized valence bond (GVB) wave function lifts this restriction, including all of the five spin functions for the six electrons involved in the bond. For N2, we find that the perfect pairing spin function is indeed dominant at Re but that it becomes progressively less so from N2 to P2 and As2. Although the perfect pairing spin function is still the most important spin function in P2, the importance of a quasi-atomic spin function, which singlet couples the spins of the electrons in the σ orbitals while high spin coupling those of the electrons in the π orbitals on each center, has significantly increased relative to N2 and, in As2, the perfect pairing and quasi-atomic spin couplings are on essentially the same footing. This change in the spin coupling of the electrons in the bonding orbitals down the periodic table may contribute to the rather dramatic decrease in the strengths of the Pn2 bonds from N2 to As2 as well as in the increase in their chemical reactivity and should be taken into account in more detailed analyses of the bond energies in these species. We also compare the spin coupling in N2 with that in C2, where the quasi-atomic spin coupling dominants around Re.

Spin wave filtering and guiding in Permalloy/iron nanowires

NASA Astrophysics Data System (ADS)

Silvani, R.; Kostylev, M.; Adeyeye, A. O.; Gubbiotti, G.

2018-03-01

We have investigated the spin wave filtering and guiding properties of periodic array of single (Permalloy and Fe) and bi-layer (Py/Fe) nanowires (NWs) by means of Brillouin light scattering measurements and micromagnetic simulations. For all the nanowire arrays, the thickness of the layers is 10 nm while all NWs have the same width of 340 nm and edge-to-edge separation of 100 nm. Spin wave dispersion has been measured in the Damon-Eshbach configuration for wave vector either parallel or perpendicular to the nanowire length. This study reveals the filtering property of the spin waves when the wave vector is perpendicular to the NW length, with frequency ranges where the spin wave propagation is permitted separated by frequency band gaps, and the guiding property of NW when the wave vector is oriented parallel to the NW, with spin wave modes propagating in parallel channels in the central and edge regions of the NW. The measured dispersions were well reproduced by micromagnetic simulations, which also deliver the spatial profiles for the modes at zero wave vector. To reproduce the dispersion of the modes localized close to the NW edges, uniaxial anisotropy has been introduced. In the case of Permalloy/iron NWs, the obtained results have been compared with those for a 20 nm thick effective NW having average magnetic properties of the two materials.

Stability of standing spin wave in permalloy thin film studied by anisotropic magnetoresistance effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamanoi, K.; Yokotani, Y.; Cui, X.

2015-12-21

We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of themore » standing spin wave is an important advantage for the high power operation of the spin-wave device.« less

Exciton Polaritons in a Two-Dimensional Lieb Lattice with Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Whittaker, C. E.; Cancellieri, E.; Walker, P. M.; Gulevich, D. R.; Schomerus, H.; Vaitiekus, D.; Royall, B.; Whittaker, D. M.; Clarke, E.; Iorsh, I. V.; Shelykh, I. A.; Skolnick, M. S.; Krizhanovskii, D. N.

2018-03-01

We study exciton polaritons in a two-dimensional Lieb lattice of micropillars. The energy spectrum of the system features two flat bands formed from S and Px ,y photonic orbitals, into which we trigger bosonic condensation under high power excitation. The symmetry of the orbital wave functions combined with photonic spin-orbit coupling gives rise to emission patterns with pseudospin texture in the flat band condensates. Our Letter shows the potential of polariton lattices for emulating flat band Hamiltonians with spin-orbit coupling, orbital degrees of freedom, and interactions.

Exciton Polaritons in a Two-Dimensional Lieb Lattice with Spin-Orbit Coupling.

PubMed

Whittaker, C E; Cancellieri, E; Walker, P M; Gulevich, D R; Schomerus, H; Vaitiekus, D; Royall, B; Whittaker, D M; Clarke, E; Iorsh, I V; Shelykh, I A; Skolnick, M S; Krizhanovskii, D N

2018-03-02

We study exciton polaritons in a two-dimensional Lieb lattice of micropillars. The energy spectrum of the system features two flat bands formed from S and P_{x,y} photonic orbitals, into which we trigger bosonic condensation under high power excitation. The symmetry of the orbital wave functions combined with photonic spin-orbit coupling gives rise to emission patterns with pseudospin texture in the flat band condensates. Our Letter shows the potential of polariton lattices for emulating flat band Hamiltonians with spin-orbit coupling, orbital degrees of freedom, and interactions.

The tight binding model study of the role of anisotropic AFM spin ordering in the charge ordered CMR manganites

NASA Astrophysics Data System (ADS)

Kar, J. K.; Panda, Saswati; Rout, G. C.

2017-05-01

We propose here a tight binding model study of the interplay between charge and spin orderings in the CMR manganites taking anisotropic effect due to electron hoppings and spin exchanges. The Hamiltonian consists of the kinetic energies of eg and t2g electrons of manganese ion. It further includes double exchange and Heisenberg interactions. The charge density wave interaction (CDW) describes an extra mechanism for the insulating character of the system. The CDW gap and spin parameters are calculated using Zubarev's Green's function technique and computed self-consistently. The results are reported in this communication.

Ab Initio study on structural, electronic, magnetic and dielectric properties of LSNO within Density Functional Perturbation Theory

NASA Astrophysics Data System (ADS)

Petersen, John; Bechstedt, Friedhelm; Furthmüller, Jürgen; Scolfaro, Luisa

LSNO (La2-xSrxNiO4) is of great interest due to its colossal dielectric constant (CDC) and rich underlying physics. While being an antiferromagnetic insulator, localized holes are present in the form of stripes in the Ni-O planes which are commensurate with the inverse of the Sr concentration. The stripes are a manifestation of charge density waves with period approximately 1/x and spin density waves with period approximately 2/x. Here, the spin ground state is calculated via LSDA + U with the PAW method implemented in VASP. Crystal structure and the effective Hubbard U parameter are optimized before calculating ɛ∞ within the independent particle approximation. ɛ∞ and the full static dielectric constant (including the lattice polarizability) ɛ0 are calculated within Density Functional Perturbation Theory.

Influence of tantalum underlayer on magnetization dynamics in Ni{sub 81}Fe{sub 19} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Jae Hyun; Deorani, Praveen; Yoon, Jungbum

2015-07-13

The effect of tantalum (Ta) underlayer is investigated in Ni{sub 81}Fe{sub 19} thin films for magnetization dynamics. The damping parameters extracted from spin wave measurements increase systematically with increasing Ta thickness, whereas the damping parameters from ferromagnetic resonance measurements are found to be weakly dependent on the Ta thickness. The difference is attributed to propagating properties of spin wave and short spin diffusion length in Ta. The group velocity of spin waves is found to be constant for different Ta thicknesses, and nonreciprocity of spin waves is not affected by the Ta thickness. The experimental observations are supported by micromagneticmore » simulations.« less

Extending geometrical optics: A Lagrangian theory for vector waves

NASA Astrophysics Data System (ADS)

Ruiz, D. E.

2016-10-01

Even diffraction aside, the commonly known equations of geometrical optics (GO) are not entirely accurate. GO considers wave rays as classical particles, which are completely described by their coordinates and momenta, but rays have another degree of freedom, namely, polarization. As a result, wave rays can behave as particles with spin. A well-known example of polarization dynamics is wave-mode conversion, which can be interpreted as rotation of the (classical) ``wave spin.'' However, there are other less-known manifestations of the wave spin, such as polarization precession and polarization-driven bending of ray trajectories. This talk presents recent advances in extending and reformulating GO as a first-principle Lagrangian theory, whose effective-gauge Hamiltonian governs both mentioned polarization phenomena simultaneously. Examples and numerical results are presented. When applied to classical waves, the theory correctly predicts the polarization-driven divergence of left- and right- polarized electromagnetic waves in isotropic media, such as dielectrics and nonmagnetized plasmas. In the case of particles with spin, the formalism also yields a point-particle Lagrangian model for the Dirac electron, i.e. the relativistic spin-1/2 electron, which includes both the Stern-Gerlach spin potential and the Bargmann-Michel-Telegdi spin precession. Additionally, the same theory contributes, perhaps unexpectedly, to the understanding of ponderomotive effects in both wave and particle dynamics; e.g., the formalism allows to obtain the ponderomotive Hamiltonian for a Dirac electron interacting with an arbitrarily large electromagnetic laser field with spin effects included. Supported by the NNSA SSAA Program through DOE Research Grant No. DE-NA0002948, by the U.S. DOE through Contract No. DE-AC02-09CH11466, and by the U.S. DOD NDSEG Fellowship through Contract No. 32-CFR-168a.

Decoherence and Determinism in a One-Dimensional Cloud-Chamber Model

NASA Astrophysics Data System (ADS)

Sparenberg, Jean-Marc; Gaspard, David

2018-03-01

The hypothesis (Sparenberg et al. in EPJ Web Conf 58:01016, [1]. https://doi.org/10.1051/epjconf/20135801016) that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the (random) positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model (Carlone et al. Comm Comput Phys 18:247, [2]. https://doi.org/10.4208/cicp.270814.311214a). In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministically according to the Schrödinger equation. We first revisit these results using a time-dependent approach, where the wave packets impinge on a symmetric two-sided detector. We discuss the evolution of the wave function in the configuration space and stress the interest of a non-symmetric detector in a quantum-measurement perspective. Next we use a time-independent approach to study the scattering of a plane wave on a single-sided detector. Preliminary results are obtained, analytically for the single-spin case and numerically for up to 8 spins. They show that the spin-excitation probabilities are sometimes very sensitive to the parameters of the model, which corroborates the idea that the measurement result could be determined by the atom positions. The possible origin of decoherence and entropy increase in future models is finally discussed.

Microscopic theory of exchange and dipole-exchange spin waves in magnetic thin films

NASA Astrophysics Data System (ADS)

Pereira, Joao Milton, Jr.

The aim of this work is to develop a microscopic theory of bulk and surface spin wave modes (or magnons) in thin films of some specific ordered magnetic materials, particularly antiferromagnets. Both exchange and magnetic dipole-dipole interactions are taken into account, depending on the material and the wavevector regime. First we study the dispersion relations of spin waves for situations in which the dominant interaction is the short-range exchange coupling between the magnetic sites. We begin by investigating ferromagnetic films with a cubic body centered (b.c.c.) crystal structure a surfaces corresponding to (111) crystal planes. The spin wave frequencies are calculated by a method that generalizes previous techniques used for simpler systems, which allows us to find analytical solutions. The results are then compared with recent experimental data for Ni films grown epitaxially on a W substrate. Then we investigate spin waves in antiferromagnetic systems. Calculations are made for the dispersion relations of exchange-dominated spin waves in antiferromagnetic thin films with simple cubic (s.c.) crystal structures, for three different surface orientations, namely (001), (101) and (111). The results are obtained by using a method similar to the one developed for the ferromagnetic film in the previous chapter. We calculate the effect of finite film thickness in coupling the spin wave modes localized near the two surfaces, leading to a splitting of several of the mode branches that occur in the semi-infinite limit. Another aspect that we consider is the influence, for the (101) orientation, of the direction of propagation on the spin wave frequencies, as well as the effect of non-equivalent sublattices in the (111) case. Next, we investigate the spin waves in antiferromagnetic films made of materials in which the long-range dipole-dipole interaction between the magnetic sites is included, along with the exchange coupling. In this case, we employ a Hamiltonian formalism that uses a transformation of the spin operators to creation and annihilation operators. Initially, we calculate the linear dipole-exchange spin wave spectrum, by considering only the bilinear terms in the transformed Hamiltonian. The theory is applied to antiferromagnetic films with s.c. and b.c.c. structures. The higher-order terms are later included by means of a diagrammatic perturbation technique, which allows us to obtain expressions for the damping and energy shift of the spin wave modes in b.c.c. antiferromagnetic films. Numerical results are then shown for ultrathin films of the antiferromagnet MnF2.

Anisotropic optical absorption induced by Rashba spin-orbit coupling in monolayer phosphorene

NASA Astrophysics Data System (ADS)

Li, Yuan; Li, Xin; Wan, Qi; Bai, R.; Wen, Z. C.

2018-04-01

We obtain the effective Hamiltonian of the phosphorene including the effect of Rashba spin-orbit coupling in the frame work of the low-energy theory. The spin-splitting energy bands show an anisotropy feature for the wave vectors along kx and ky directions, where kx orients to ΓX direction in the k space. We numerically study the optical absorption of the electrons for different wave vectors with Rashba spin-orbit coupling. We find that the spin-flip transition from the valence band to the conduction band induced by the circular polarized light closes to zero with increasing the x-component wave vector when ky equals to zero, while it can be significantly increased to a large value when ky gets a small value. When the wave vector varies along the ky direction, the spin-flip transition can also increase to a large value, however, which shows an anisotropy feature for the optical absorption. Especially, the spin-conserved transitions keep unchanged and have similar varying trends for different wave vectors. This phenomenon provides a novel route for the manipulation of the spin-dependent property of the fermions in the monolayer phosphorene.

Spin polarization of graphene and h -BN on Co(0001) and Ni(111) observed by spin-polarized surface positronium spectroscopy

NASA Astrophysics Data System (ADS)

Miyashita, A.; Maekawa, M.; Wada, K.; Kawasuso, A.; Watanabe, T.; Entani, S.; Sakai, S.

2018-05-01

In spin-polarized surface positronium annihilation measurements, the spin polarizations of graphene and h -BN on Co(0001) were higher than those on Ni(111), while no significant differences were seen between graphene and h -BN on the same metal. The obtained spin polarizations agreed with those expected from first-principles calculations considering the positron wave function and the electron density of states from the first surface layer to the vacuum region. The higher spin polarizations of graphene and h -BN on Co(0001) as compared to Ni(111) simply reflect the spin polarizations of these metals. The comparable spin polarizations of graphene and h -BN on the same metal are attributed to the creation of similar electronic states due to the strong influence of the metals: the Dirac cone of graphene and the band gap of h -BN disappear as a consequence of d -π hybridization.

Langmuir instability in partially spin polarized bounded degenerate plasma

NASA Astrophysics Data System (ADS)

Iqbal, Z.; Jamil, M.; Murtaza, G.

2018-04-01

Some new features of waves inside the cylindrical waveguide on employing the separated spin evolution quantum hydrodynamic model are evoked. Primarily, the instability of Langmuir wave due to the electron beam in a partially spin polarized degenerate plasma considering a nano-cylindrical geometry is discussed. Besides, the evolution of a new spin-dependent wave (spin electron acoustic wave) due to electron spin polarization effects in the real wave spectrum is elaborated. Analyzing the growth rate, it is found that in the absence of Bohm potential, the electron spin effects or exchange interaction reduce the growth rate as well as k-domain but the inclusion of Bohm potential increases both the growth rate and k-domain. Further, we investigate the geometry effects expressed by R and pon and find that they have opposite effects on the growth rate and k-domain of the instability. Additionally, how the other parameters like electron beam density or streaming speed of beam electrons influence the growth rate is also investigated. This study may find its applications for the signal analysis in solid state devices at nanoscales.

Spin waves and magnetic exchange interactions in the spin-ladder compound RbFe 2 Se 3

DOE PAGES

Wang, Meng; Yi, Ming; Jin, Shangjian; ...

2016-07-20

In this paper, we report an inelastic neutron scattering study of the spin waves of the one-dimensional antiferromagnetic spin ladder compound RbFe 2Se 3. The results reveal that the products, SJ's, of the spin S and the magnetic exchange interaction J along the antiferromagnetic (leg) direction and the ferromagnetic (rung) direction are comparable with those for the stripe ordered phase of the parent compounds of the iron-based superconductors. Also, the universality of the SJ's implies nearly universal spin wave dynamics and the irrelevance of the fermiology for the existence of the stripe antiferromagnetic order among various Fe-based materials.

Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbiotti, G.; Tacchi, S.; Montoncello, F.

2015-06-29

The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained bymore » dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.« less

Dynamics of a magnetic skyrmionium driven by spin waves

NASA Astrophysics Data System (ADS)

Li, Sai; Xia, Jing; Zhang, Xichao; Ezawa, Motohiko; Kang, Wang; Liu, Xiaoxi; Zhou, Yan; Zhao, Weisheng

2018-04-01

A magnetic skyrmionium is a skyrmion-like structure, but carries a zero net skyrmion number which can be used as a building block for non-volatile information processing devices. Here, we study the dynamics of a magnetic skyrmionium driven by propagating spin waves. It is found that the skyrmionium can be effectively driven into motion by spin waves showing a tiny skyrmion Hall effect, whose mobility is much better than that of the skyrmion at the same condition. We also show that the skyrmionium mobility depends on the nanotrack width and the damping coefficient and can be controlled by an external out-of-plane magnetic field. In addition, we demonstrate that the skyrmionium motion driven by spin waves is inertial. Our results indicate that the skyrmionium is a promising building block for building spin-wave spintronic devices.

Spin wave propagation detected over 100 μm in half-metallic Heusler alloy Co2MnSi

NASA Astrophysics Data System (ADS)

Stückler, Tobias; Liu, Chuanpu; Yu, Haiming; Heimbach, Florian; Chen, Jilei; Hu, Junfeng; Tu, Sa; Alam, Md. Shah; Zhang, Jianyu; Zhang, Youguang; Farrell, Ian L.; Emeny, Chrissy; Granville, Simon; Liao, Zhi-Min; Yu, Dapeng; Zhao, Weisheng

2018-03-01

The field of magnon spintronics offers a charge current free way of information transportation by using spin waves (SWs). Compared to forward volume spin waves for example, Damon-Eshbach (DE) SWs need a relatively weak external magnetic field which is suitable for small spintronic devices. In this work we study DE SWs in Co2MnSi, a half-metallic Heusler alloy with significant potential for magnonics. Thin films have been produced by pulsed laser deposition. Integrated coplanar waveguide (CPW) antennas with different distances between emitter and detection antenna have been prepared on a Co2MnSi film. We used a vector network analyzer to measure spin wave reflection and transmission. We observe spin wave propagation up to 100 μm, a new record for half-metallic Heusler thin films.

Manipulation of propagating spin waves in straight and curved magnetic microstrips

NASA Astrophysics Data System (ADS)

Haldar, Arabinda; Liu, Hau-Jian; Schultheiss, Helmut; Vogt, Katrin; Hoffmann, Axel; Buchanan, Kristen

2012-02-01

The main challenges in realizing magnonics devices are the generation, manipulation and detection of spin waves, especially in metallic magnetic materials where the length scales are of interest for applications. We have studied the propagation of spin waves in transversely magnetized Permalloy (Py) microstrips of different shapes using micro-Brillouin light scattering. The Py stripe was 30-nm thick, several micrometers wide and >50 μm long. Spin waves were excited in the Py strip using a 2-μm wide antenna. We compare the spin wave propagation along a straight wire to the propagation along a magnetic microstrip with a smooth bend. We will also discuss the use of a current through a gold wire under the Permalloy to provide a local magnetic field to maintain a transverse magnetization around the bend.

Spin-wave resonance frequency in ferromagnetic thin film with interlayer exchange coupling and surface anisotropy

NASA Astrophysics Data System (ADS)

Zhang, Shuhui; Rong, Jianhong; Wang, Huan; Wang, Dong; Zhang, Lei

2018-01-01

We have investigated the dependence of spin-wave resonance(SWR) frequency on the surface anisotropy, the interlayer exchange coupling, the ferromagnetic layer thickness, the mode number and the external magnetic field in a ferromagnetic superlattice film by means of the linear spin-wave approximation and Green's function technique. The SWR frequency of the ferromagnetic thin film is shifted to higher values corresponding to those of above factors, respectively. It is found that the linear behavior of SWR frequency curves of all modes in the system is observed as the external magnetic field is increasing, however, SWR frequency curves are nonlinear with the lower and the higher modes for different surface anisotropy and interlayer exchange coupling in the system. In addition, the SWR frequency of the lowest (highest) mode is shifted to higher (lower) values when the film thickness is thinner. The interlayer exchange coupling is more important for the energetically higher modes than for the energetically lower modes. The surface anisotropy has a little effect on the SWR frequency of the highest mode, when the surface anisotropy field is further increased.

Detecting binary neutron star systems with spin in advanced gravitational-wave detectors

NASA Astrophysics Data System (ADS)

Brown, Duncan A.; Harry, Ian; Lundgren, Andrew; Nitz, Alexander H.

2012-10-01

The detection of gravitational waves from binary neutron stars is a major goal of the gravitational-wave observatories Advanced LIGO and Advanced Virgo. Previous searches for binary neutron stars with LIGO and Virgo neglected the component stars’ angular momentum (spin). We demonstrate that neglecting spin in matched-filter searches causes advanced detectors to lose more than 3% of the possible signal-to-noise ratio for 59% (6%) of sources, assuming that neutron star dimensionless spins, cJ/GM2, are uniformly distributed with magnitudes between 0 and 0.4 (0.05) and that the neutron stars have isotropically distributed spin orientations. We present a new method for constructing template banks for gravitational-wave searches for systems with spin. We present a new metric in a parameter space in which the template placement metric is globally flat. This new method can create template banks of signals with nonzero spins that are (anti-)aligned with the orbital angular momentum. We show that this search loses more than 3% of the maximum signal-to-noise for only 9% (0.2%) of binary neutron star sources with dimensionless spins between 0 and 0.4 (0.05) and isotropic spin orientations. Use of this template bank will prevent selection bias in gravitational-wave searches and allow a more accurate exploration of the distribution of spins in binary neutron stars.

On the motion of a quantum particle in the spinning cosmic string space–time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassanabadi, H., E-mail: h.hasanabadi@shahroodut.ac.ir; Afshardoost, A.; Zarrinkamar, S.

2015-05-15

We analyze the energy spectrum and the wave function of a particle subjected to magnetic field in the spinning cosmic string space–time and investigate the influence of the spinning reference frame and topological defect on the system. To do this we solve Schrödinger equation in the spinning cosmic string background. In our work, instead of using an approximation in the calculations, we use the quasi-exact ansatz approach which gives the exact solutions for some primary levels. - Highlights: • Solving the Schrödinger equation in the spinning cosmic string space time. • Proposing a quasi-exact analytical solution to the general formmore » of the corresponding equation. • Generalizing the previous works.« less

Current-induced instability of domain walls in cylindrical nanowires

NASA Astrophysics Data System (ADS)

Wang, Weiwei; Zhang, Zhaoyang; Pepper, Ryan A.; Mu, Congpu; Zhou, Yan; Fangohr, Hans

2018-01-01

We study the current-driven domain wall (DW) motion in cylindrical nanowires using micromagnetic simulations by implementing the Landau-Lifshitz-Gilbert equation with nonlocal spin-transfer torque in a finite difference micromagnetic package. We find that in the presence of DW, Gaussian wave packets (spin waves) will be generated when the charge current is suddenly applied to the system. This effect is excluded when using the local spin-transfer torque. The existence of spin waves emission indicates that transverse domain walls can not move arbitrarily fast in cylindrical nanowires although they are free from the Walker limit. We establish an upper velocity limit for DW motion by analyzing the stability of Gaussian wave packets using the local spin-transfer torque. Micromagnetic simulations show that the stable region obtained by using nonlocal spin-transfer torque is smaller than that by using its local counterpart. This limitation is essential for multiple DWs since the instability of Gaussian wave packets will break the structure of multiple DWs.

Magnonic waveguide based on exchange-spring magnetic structure

NASA Astrophysics Data System (ADS)

Wang, Lixiang; Gao, Leisen; Jin, Lichuan; Liao, Yulong; Wen, Tianlong; Tang, Xiaoli; Zhang, Huaiwu; Zhong, Zhiyong

2018-05-01

A soft/hard exchange-spring coupled bilayer magnetic structure is proposed to obtain a narrow channel for spin-wave propagation. Micromagnetic simulations show that broad-band Damon-Eshbach geometry spin waves are strongly constrained within the channel and propagate effectively with a high group velocity. The beam width of the bound spin waves is almost independent from the frequency and is smaller than 24nm. Two side spin beams appearing at the low-frequency excitation are demonstrated to be coupled with the channel spins by dipole-dipole interaction. In contrast to a domain wall, the channel formed by exchange-spring coupling is easier to be realized in experimental scenarios and holds stronger immunity to surroundings. This work is expected to open new possibilities for energy-efficient spin-wave guiding as well as to help shape the field of beam magnonics.

Design and development of the spinning mode synthesizer

NASA Technical Reports Server (NTRS)

Seiner, J. M.; Reethof, G.

1973-01-01

Design and development of a flexible source of spinning modes which is capable of generating independent spinning waves of controlled complexity and spin speed without the introduction of broad band elements is reported. These features were accomplished through the use of eight commercial loudspeakers located in an equally spaced circular array with diameter of 11 inches and properly phased so that the system could generate a spinning wave. The constructed apparatus was tested in an anechoic environment and found capable of generating a plane, one and two lobed spinning wave of high quality with a sound pressure level of 120 db and at frequencies ranging from 1500 to 2500 Hz at a distance of 4 ft in the far field. The wave speeds investigated varied from 8000 to 18000 rad/sec which represent supersonic peripheral speeds.

Chemical Bonding: The Orthogonal Valence-Bond View

PubMed Central

Sax, Alexander F.

2015-01-01

Chemical bonding is the stabilization of a molecular system by charge- and spin-reorganization processes in chemical reactions. These processes are said to be local, because the number of atoms involved is very small. With multi-configurational self-consistent field (MCSCF) wave functions, these processes can be calculated, but the local information is hidden by the delocalized molecular orbitals (MO) used to construct the wave functions. The transformation of such wave functions into valence bond (VB) wave functions, which are based on localized orbitals, reveals the hidden information; this transformation is called a VB reading of MCSCF wave functions. The two-electron VB wave functions describing the Lewis electron pair that connects two atoms are frequently called covalent or neutral, suggesting that these wave functions describe an electronic situation where two electrons are never located at the same atom; such electronic situations and the wave functions describing them are called ionic. When the distance between two atoms decreases, however, every covalent VB wave function composed of non-orthogonal atomic orbitals changes its character from neutral to ionic. However, this change in the character of conventional VB wave functions is hidden by its mathematical form. Orthogonal VB wave functions composed of orthonormalized orbitals never change their character. When localized fragment orbitals are used instead of atomic orbitals, one can decide which local information is revealed and which remains hidden. In this paper, we analyze four chemical reactions by transforming the MCSCF wave functions into orthogonal VB wave functions; we show how the reactions are influenced by changing the atoms involved or by changing their local symmetry. Using orthogonal instead of non-orthogonal orbitals is not just a technical issue; it also changes the interpretation, revealing the properties of wave functions that remain otherwise undetected. PMID:25906476

Search for gravitational waves from binary black hole inspiral, merger, and ringdown

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Arain, M. A.; Araya, M. C.; Aronsson, M.; Aso, Y.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballinger, T.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Beker, M. G.; Belletoile, A.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Boccara, C.; Bock, O.; Bodiya, T. P.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chaibi, O.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coulon, J.-P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Das, K.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Davis, A.; Daw, E. J.; Day, R.; Dayanga, T.; Derosa, R.; Debra, D.; Debreczeni, G.; Degallaix, J.; Del Prete, M.; Dergachev, V.; de Rosa, R.; Desalvo, R.; Devanka, P.; Dhurandhar, S.; di Fiore, L.; di Lieto, A.; di Palma, I.; di Paolo Emilio, M.; di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dueck, J.; Dumas, J.-C.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Ely, G.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Flasch, K.; Foley, S.; Forrest, C.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Gholami, I.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hall, P.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A. W.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hoyland, D.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J. B.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, H.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Krause, T.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kullman, J.; Kumar, R.; Kwee, P.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lin, H.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubiński, M.; Lucianetti, A.; Lück, H.; Lundgren, A. D.; Machenschalk, B.; Macinnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Mak, C.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIvor, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Morioka, T.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Pardi, S.; Pareja, M.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radke, T.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Sammut, L.; Sancho de La Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stein, A. J.; Stein, L. C.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Tseng, K.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2011-06-01

We present the first modeled search for gravitational waves using the complete binary black-hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data, taken between November 2005 and September 2007, for systems with component masses of 1-99M⊙ and total masses of 25-100M⊙. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for 19M⊙≤m1, m2≤28M⊙ binary black-hole systems with negligible spin to be no more than 2.0Mpc-3Myr-1 at 90% confidence.

Spin-isospin excitation of 3He with three-proton final state

NASA Astrophysics Data System (ADS)

Ishikawa, Souichi

2018-01-01

Spin-isospin excitation of the {}^3He nucleus by a proton-induced charge exchange reaction, {}^3He(p,n)ppp, at forward neutron scattering angle is studied in a plane wave impulse approximation (PWIA). In PWIA, cross sections of the reaction are written in terms of proton-neutron scattering amplitudes and response functions of the transition from {}3He to the three-proton state by spin-isospin transition operators. The response functions are calculated with realistic nucleon-nucleon potential models using a Faddeev three-body method. Calculated cross sections agree with available experimental data in substance. Possible effects arising from the uncertainty of proton-neutron amplitudes and three-nucleon interactions in the three-proton system are examined.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostylev, M.

In this work, we derive the interface exchange boundary conditions for the classical linear dynamics of magnetization in ferromagnetic layers with the interface Dzyaloshinskii-Moriya interaction (IDMI). We show that IDMI leads to pinning of dynamic magnetization at the interface. An unusual peculiarity of the IDMI-based pinning is that its scales as the spin-wave wave number. We incorporate these boundary conditions into an existing numerical model for the dynamics of the Damon-Eshbach spin wave in ferromagnetic films. IDMI affects the dispersion and the frequency non-reciprocity of the travelling Damon-Eshbach spin wave. For a broad range of film thicknesses L and wavemore » numbers, the results of the numerical simulations of the spin wave dispersion are in a good agreement with a simple analytical expression, which shows that the contribution of IDMI to the dispersion scales as 1/L, similarly to the effect of other types of interfacial anisotropy. Suggestions to experimentalists how to detect the presence of IDMI in a spin wave experiment are given.« less

Lagrangian geometrical optics of nonadiabatic vector waves and spin particles

DOE PAGES

Ruiz, D. E.; Dodin, I. Y.

2015-07-29

Linear vector waves, both quantum and classical, experience polarization-driven bending of ray trajectories and polarization dynamics that can be interpreted as the precession of the "wave spin". Here, both phenomena are governed by an effective gauge Hamiltonian vanishing in leading-order geometrical optics. This gauge Hamiltonian can be recognized as a generalization of the Stern-Gerlach Hamiltonian that is commonly known for spin-1/2 quantum particles. The corresponding reduced Lagrangians for continuous nondissipative waves and their geometrical-optics rays are derived from the fundamental wave Lagrangian. The resulting Euler-Lagrange equations can describe simultaneous interactions of N resonant modes, where N is arbitrary, and leadmore » to equations for the wave spin, which happens to be an (N 2 - 1)-dimensional spin vector. As a special case, classical equations for a Dirac particle (N = 2) are deduced formally, without introducing additional postulates or interpretations, from the Dirac quantum Lagrangian with the Pauli term. The model reproduces the Bargmann-Michel-Telegdi equations with added Stern-Gerlach force.« less

Distribution of Localized States from Fine Analysis of Electron Spin Resonance Spectra in Organic Transistors

NASA Astrophysics Data System (ADS)

Matsui, Hiroyuki; Mishchenko, Andrei S.; Hasegawa, Tatsuo

2010-02-01

We developed a novel method for obtaining the distribution of trapped carriers over their degree of localization in organic transistors, based on the fine analysis of electron spin resonance spectra at low enough temperatures where all carriers are localized. To apply the method to pentacene thin-film transistors, we proved through continuous wave saturation experiments that all carriers are localized at below 50 K. We analyzed the spectra at 20 K and found that the major groups of traps comprise localized states having wave functions spanning around 1.5 and 5 molecules and a continuous distribution of states with spatial extent in the range between 6 and 20 molecules.

Distribution of localized states from fine analysis of electron spin resonance spectra in organic transistors.

PubMed

Matsui, Hiroyuki; Mishchenko, Andrei S; Hasegawa, Tatsuo

2010-02-05

We developed a novel method for obtaining the distribution of trapped carriers over their degree of localization in organic transistors, based on the fine analysis of electron spin resonance spectra at low enough temperatures where all carriers are localized. To apply the method to pentacene thin-film transistors, we proved through continuous wave saturation experiments that all carriers are localized at below 50 K. We analyzed the spectra at 20 K and found that the major groups of traps comprise localized states having wave functions spanning around 1.5 and 5 molecules and a continuous distribution of states with spatial extent in the range between 6 and 20 molecules.

Spin pumping and inverse spin Hall effects in heavy metal/antiferromagnet/Permalloy trilayers

NASA Astrophysics Data System (ADS)

Saglam, Hilal; Zhang, Wei; Jungfleisch, M. Benjamin; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

Recent work shows efficient spin transfer via spin waves in insulating antiferromagnets (AFMs), suggesting that AFMs can play a more active role in the manipulation of ferromagnets. We use spin pumping and inverse spin Hall effect experiments on heavy metal (Pt and W)/AFMs/Py (Ni80Fe20) trilayer structures, to examine the possible spin transfer phenomenon in metallic AFMs, i . e . , FeMn and PdMn. Previous work has studied electronic effects of the spin transport in these materials, yielding short spin diffusion length on the order of 1 nm. However, the work did not examine whether besides diffusive spin transport by the conduction electrons, there are additional spin transport contributions from spin wave excitations. We clearly observe spin transport from the Py spin reservoir to the heavy metal layer through the sandwiched AFMs with thicknesses well above the previously measured spin diffusion lengths, indicating that spin transport by spin waves may lead to non-negligible contributions This work was supported by US DOE, OS, Materials Sciences and Engineering Division. Lithographic patterning was carried out at the CNM, which is supported by DOE, OS under Contract No. DE-AC02-06CH11357.

Theory of unidirectional spin heat conveyer

NASA Astrophysics Data System (ADS)

Adachi, Hiroto; Maekawa, Sadamichi

2015-05-01

We theoretically investigate the unidirectional spin heat conveyer effect recently reported in the literature that emerges from the Damon-Eshbach spin wave on the surface of a magnetic material. We develop a simple phenomenological theory for heat transfer dynamics in a coupled system of phonons and the Damon-Eshbach spin wave, and demonstrate that there arises a direction-selective heat flow as a result of the competition between an isotropic heat diffusion by phonons and a unidirectional heat drift by the spin wave. The phenomenological approach can account for the asymmetric local temperature distribution observed in the experiment.

Theory of unidirectional spin heat conveyer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adachi, Hiroto, E-mail: adachi.hiroto@jaea.go.jp; Maekawa, Sadamichi

2015-05-07

We theoretically investigate the unidirectional spin heat conveyer effect recently reported in the literature that emerges from the Damon-Eshbach spin wave on the surface of a magnetic material. We develop a simple phenomenological theory for heat transfer dynamics in a coupled system of phonons and the Damon-Eshbach spin wave, and demonstrate that there arises a direction-selective heat flow as a result of the competition between an isotropic heat diffusion by phonons and a unidirectional heat drift by the spin wave. The phenomenological approach can account for the asymmetric local temperature distribution observed in the experiment.

Overcoming thermal noise in non-volatile spin wave logic.

PubMed

Dutta, Sourav; Nikonov, Dmitri E; Manipatruni, Sasikanth; Young, Ian A; Naeemi, Azad

2017-05-15

Spin waves are propagating disturbances in magnetically ordered materials, analogous to lattice waves in solid systems and are often described from a quasiparticle point of view as magnons. The attractive advantages of Joule-heat-free transmission of information, utilization of the phase of the wave as an additional degree of freedom and lower footprint area compared to conventional charge-based devices have made spin waves or magnon spintronics a promising candidate for beyond-CMOS wave-based computation. However, any practical realization of an all-magnon based computing system must undergo the essential steps of a careful selection of materials and demonstrate robustness with respect to thermal noise or variability. Here, we aim at identifying suitable materials and theoretically demonstrate the possibility of achieving error-free clocked non-volatile spin wave logic device, even in the presence of thermal noise and clock jitter or clock skew.

Generation of propagating spin waves from regions of increased dynamic demagnetising field near magnetic antidots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, C. S., E-mail: csd203@exeter.ac.uk; Kruglyak, V. V.; Sadovnikov, A. V.

We have used Brillouin Light Scattering and micromagnetic simulations to demonstrate a point-like source of spin waves created by the inherently nonuniform internal magnetic field in the vicinity of an isolated antidot formed in a continuous film of yttrium-iron-garnet. The field nonuniformity ensures that only well-defined regions near the antidot respond in resonance to a continuous excitation of the entire sample with a harmonic microwave field. The resonantly excited parts of the sample then served as reconfigurable sources of spin waves propagating (across the considered sample) in the form of caustic beams. Our findings are relevant to further development ofmore » magnonic circuits, in which point-like spin wave stimuli could be required, and as a building block for interpretation of spin wave behavior in magnonic crystals formed by antidot arrays.« less

Spin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Siegfried, S.-A.; Sukhanov, A. S.; Altynbaev, E. V.; Honecker, D.; Heinemann, A.; Tsvyashchenko, A. V.; Grigoriev, S. V.

2017-04-01

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to TC≈278.7 K by small-angle neutron scattering. The method we have used is based on [Grigoriev et al., Phys. Rev. B 92, 220415(R) (2015), 10.1103/PhysRevB.92.220415] and was extended here for the application in polycrystalline samples. We confirm the validity of the anisotropic spin-wave dispersion for FeGe caused by the Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness A for the FeGe helimagnet decreases with a temperature as A (T ) =194 [1 -0.7 (T/TC) 4.2] meVÅ 2 . The finite value of the spin-wave stiffness A =58 meVÅ 2 at TC classifies the order-disorder phase transition in FeGe as being the first-order one.

Long-range mutual synchronization of spin Hall nano-oscillators

NASA Astrophysics Data System (ADS)

Awad, A. A.; Dürrenfeld, P.; Houshang, A.; Dvornik, M.; Iacocca, E.; Dumas, R. K.; Åkerman, J.

2017-03-01

The spin Hall effect in a non-magnetic metal with spin-orbit coupling injects transverse spin currents into adjacent magnetic layers, where the resulting spin transfer torque can drive spin wave auto-oscillations. Such spin Hall nano-oscillators (SHNOs) hold great promise as extremely compact and broadband microwave signal generators and magnonic spin wave injectors. Here we show that SHNOs can also be mutually synchronized with unprecedented efficiency. We demonstrate mutual synchronization of up to nine individual SHNOs, each separated by 300 nm. Through further tailoring of the connection regions we can extend the synchronization range to 4 μm. The mutual synchronization is observed electrically as an increase in the power and coherence of the microwave signal, and confirmed optically using micro-Brillouin light scattering microscopy as two spin wave regions sharing the same spectral content, in agreement with our micromagnetic simulations.

OPTICS. Quantum spin Hall effect of light.

PubMed

Bliokh, Konstantin Y; Smirnova, Daria; Nori, Franco

2015-06-26

Maxwell's equations, formulated 150 years ago, ultimately describe properties of light, from classical electromagnetism to quantum and relativistic aspects. The latter ones result in remarkable geometric and topological phenomena related to the spin-1 massless nature of photons. By analyzing fundamental spin properties of Maxwell waves, we show that free-space light exhibits an intrinsic quantum spin Hall effect—surface modes with strong spin-momentum locking. These modes are evanescent waves that form, for example, surface plasmon-polaritons at vacuum-metal interfaces. Our findings illuminate the unusual transverse spin in evanescent waves and explain recent experiments that have demonstrated the transverse spin-direction locking in the excitation of surface optical modes. This deepens our understanding of Maxwell's theory, reveals analogies with topological insulators for electrons, and offers applications for robust spin-directional optical interfaces. Copyright © 2015, American Association for the Advancement of Science.

Approaching soft X-ray wavelengths in nanomagnet-based microwave technology

PubMed Central

Yu, Haiming; d' Allivy Kelly, O.; Cros, V.; Bernard, R.; Bortolotti, P.; Anane, A.; Brandl, F.; Heimbach, F.; Grundler, D.

2016-01-01

Seven decades after the discovery of collective spin excitations in microwave-irradiated ferromagnets, there has been a rebirth of magnonics. However, magnetic nanodevices will enable smart GHz-to-THz devices at low power consumption only, if such spin waves (magnons) are generated and manipulated on the sub-100 nm scale. Here we show how magnons with a wavelength of a few 10 nm are exploited by combining the functionality of insulating yttrium iron garnet and nanodisks from different ferromagnets. We demonstrate magnonic devices at wavelengths of 88 nm written/read by conventional coplanar waveguides. Our microwave-to-magnon transducers are reconfigurable and thereby provide additional functionalities. The results pave the way for a multi-functional GHz technology with unprecedented miniaturization exploiting nanoscale wavelengths that are otherwise relevant for soft X-rays. Nanomagnonics integrated with broadband microwave circuitry offer applications that are wide ranging, from nanoscale microwave components to nonlinear data processing, image reconstruction and wave-based logic. PMID:27063401

Isotropic transmission of magnon spin information without a magnetic field.

PubMed

Haldar, Arabinda; Tian, Chang; Adeyeye, Adekunle Olusola

2017-07-01

Spin-wave devices (SWD), which use collective excitations of electronic spins as a carrier of information, are rapidly emerging as potential candidates for post-semiconductor non-charge-based technology. Isotropic in-plane propagating coherent spin waves (magnons), which require magnetization to be out of plane, is desirable in an SWD. However, because of lack of availability of low-damping perpendicular magnetic material, a usually well-known in-plane ferrimagnet yttrium iron garnet (YIG) is used with a large out-of-plane bias magnetic field, which tends to hinder the benefits of isotropic spin waves. We experimentally demonstrate an SWD that eliminates the requirement of external magnetic field to obtain perpendicular magnetization in an otherwise in-plane ferromagnet, Ni 80 Fe 20 or permalloy (Py), a typical choice for spin-wave microconduits. Perpendicular anisotropy in Py, as established by magnetic hysteresis measurements, was induced by the exchange-coupled Co/Pd multilayer. Isotropic propagation of magnon spin information has been experimentally shown in microconduits with three channels patterned at arbitrary angles.

Anisotropic itinerant magnetism and spin fluctuations in BaFe2As2 : A neutron scattering study

NASA Astrophysics Data System (ADS)

Matan, K.; Morinaga, R.; Iida, K.; Sato, T. J.

2009-02-01

Neutron scattering measurements were performed to investigate magnetic excitations in a single-crystal sample of the ternary iron arsenide BaFe2As2 , a parent compound of a recently discovered family of Fe-based superconductors. In the ordered state, we observe low energy spin-wave excitations with a gap energy Δ=9.8(4)meV . The in-plane spin-wave velocity vab and out-of-plane spin-wave velocity vc measured at 12 meV are 280(150) and 57(7)meVÅ , respectively. At high energy, we observe anisotropic scattering centered at the antiferromagnetic wave vectors. This scattering indicates two-dimensional spin dynamics, which possibly exist inside the Stoner continuum. At TN=136(1)K , the gap closes and quasielastic scattering is observed above TN , indicative of short-range spin fluctuations. In the paramagnetic state, the scattering intensity along the L direction becomes “rodlike,” characteristic of uncorrelated out-of-plane spins, attesting to the two-dimensionality of the system.

Isotropic transmission of magnon spin information without a magnetic field

PubMed Central

Haldar, Arabinda; Tian, Chang; Adeyeye, Adekunle Olusola

2017-01-01

Spin-wave devices (SWD), which use collective excitations of electronic spins as a carrier of information, are rapidly emerging as potential candidates for post-semiconductor non-charge-based technology. Isotropic in-plane propagating coherent spin waves (magnons), which require magnetization to be out of plane, is desirable in an SWD. However, because of lack of availability of low-damping perpendicular magnetic material, a usually well-known in-plane ferrimagnet yttrium iron garnet (YIG) is used with a large out-of-plane bias magnetic field, which tends to hinder the benefits of isotropic spin waves. We experimentally demonstrate an SWD that eliminates the requirement of external magnetic field to obtain perpendicular magnetization in an otherwise in-plane ferromagnet, Ni80Fe20 or permalloy (Py), a typical choice for spin-wave microconduits. Perpendicular anisotropy in Py, as established by magnetic hysteresis measurements, was induced by the exchange-coupled Co/Pd multilayer. Isotropic propagation of magnon spin information has been experimentally shown in microconduits with three channels patterned at arbitrary angles. PMID:28776033

Oblique propagation of E.M. wave in magnetized quantum plasma with two different spin states

NASA Astrophysics Data System (ADS)

Kumar, Punit; Ahmad, Nafees; Singh, Shiv

2018-05-01

The dispersion relation for the oblique propagation of electromagnetic wave in high density homogeneous quantum plasma is established. The growth rate has been evaluated. The difference in the concentration of spin-up and spin-down electrons have taken in to account and effects of spin polarization is analyzed.

Electrically controllable spin filtering based on superconducting helical states

NASA Astrophysics Data System (ADS)

Bobkova, I. V.; Bobkov, A. M.

2017-12-01

The magnetoelectric effects in the surface states of the three-dimensional (3D) topological insulator (TI) are extremely strong due to the full spin-momentum locking. Here the microscopic theory of S/3D TI bilayer structures in terms of quasiclassical Green's functions is developed. On the basis of the developed formalism it is shown that the DOS in the S/TI bilayer manifests giant magnetoelectric behavior and, as a result, S/3D TI heterostructures can work as nonmagnetic fully electrically controllable spin filters. It is shown that due to the full spin-momentum locking the amplitudes of the odd-frequency singlet and triplet components of the condensate wave function are equal. The same is valid for the even frequency singlet and triplet components. We unveil the connection between the odd-frequency pairing in S/3D TI heterostructures and magnetoelectric effects in the DOS.

Confined states in photonic-magnonic crystals with complex unit cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dadoenkova, Yu. S.; Novgorod State University, 173003 Veliky Novgorod; Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 83114 Donetsk

2016-08-21

We have investigated multifunctional periodic structures in which electromagnetic waves and spin waves can be confined in the same areas. Such simultaneous localization of both sorts of excitations can potentially enhance the interaction between electromagnetic waves and spin waves. The system we considered has a form of one dimensional photonic-magnonic crystal with two types of magnetic layers (thicker and thinner ones) separated by sections of the dielectric photonic crystals. We focused on the electromagnetic defect modes localized in the magnetic layers (areas where spin waves can be excited) and decaying in the sections of conventional (nonmagnetic) photonic crystals. We showedmore » how the change of relative thickness of two types of the magnetic layers can influence on the spectrum of spin waves and electromagnetic defect modes, both localized in magnetic parts of the system.« less

Design of a CMOS integrated on-chip oscilloscope for spin wave characterization

NASA Astrophysics Data System (ADS)

Egel, Eugen; Meier, Christian; Csaba, György; Breitkreutz-von Gamm, Stephan

2017-05-01

Spin waves can perform some optically-inspired computing algorithms, e.g. the Fourier transform, directly than it is done with the CMOS logic. This article describes a new approach for on-chip characterization of spin wave based devices. The readout circuitry for the spin waves is simulated with 65-nm CMOS technology models. Commonly used circuits for Radio Frequency (RF) receivers are implemented to detect a sinusoidal ultra-wideband (5-50 GHz) signal with an amplitude of at least 15 μV picked up by a loop antenna. First, the RF signal is amplified by a Low Noise Amplifier (LNA). Then, it is down-converted by a mixer to Intermediate Frequency (IF). Finally, an Operational Amplifier (OpAmp) brings the IF signal to higher voltages (50-300 mV). The estimated power consumption and the required area of the readout circuit is approximately 55.5 mW and 0.168 mm2, respectively. The proposed On-Chip Oscilloscope (OCO) is highly suitable for on-chip spin wave characterization regarding the frequency, amplitude change and phase information. It offers an integrated low power alternative to current spin wave detecting systems.

Theory of superconductivity in a three-orbital model of Sr2RuO4

NASA Astrophysics Data System (ADS)

Wang, Q. H.; Platt, C.; Yang, Y.; Honerkamp, C.; Zhang, F. C.; Hanke, W.; Rice, T. M.; Thomale, R.

2013-10-01

In conventional and high transition temperature copper oxide and iron pnictide superconductors, the Cooper pairs all have even parity. As a rare exception, Sr2RuO4 is the first prime candidate for topological chiral p-wave superconductivity, which has time-reversal breaking odd-parity Cooper pairs known to exist before only in the neutral superfluid 3He. However, there are several key unresolved issues hampering the microscopic description of the unconventional superconductivity. Spin fluctuations at both large and small wave vectors are present in experiments, but how they arise and drive superconductivity is not yet clear. Spontaneous edge current is expected but not observed conclusively. Specific experiments point to highly band- and/or momentum-dependent energy gaps for quasiparticle excitations in the superconducting state. Here, by comprehensive functional renormalization group calculations with all relevant bands, we disentangle the various competing possibilities. In particular, we show the small wave vector spin fluctuations, driven by a single two-dimensional band, trigger p-wave superconductivity with quasi-nodal energy gaps.

Nonreciprocity of spin waves in magnonic crystals created by surface acoustic waves in structures with yttrium iron garnet

NASA Astrophysics Data System (ADS)

Kryshtal, R. G.; Medved, A. V.

2015-12-01

Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW - magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW - magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW - magnonic crystals are promising for signal processing in the GHz range.

Spin-polarized density-matrix functional theory of the single-impurity Anderson model

NASA Astrophysics Data System (ADS)

Töws, W.; Pastor, G. M.

2012-12-01

Lattice density functional theory (LDFT) is used to investigate spin excitations in the single-impurity Anderson model. In this method, the single-particle density matrix γijσ with respect to the lattice sites replaces the wave function as the basic variable of the many-body problem. A recently developed two-level approximation (TLA) to the interaction-energy functional W[γ] is extended to systems having spin-polarized density distributions and bond orders. This allows us to investigate the effect of external magnetic fields and, in particular, the important singlet-triplet gap ΔE, which determines the Kondo temperature. Applications to finite Anderson rings and square lattices show that the gap ΔE as well as other ground-state and excited-state properties are very accurately reproduced. One concludes that the spin-polarized TLA is reliable in all interaction regimes, from weak to strong correlations, for different hybridization strengths and for all considered impurity valence states. In this way the efficiency of LDFT to account for challenging electron-correlation effects is demonstrated.

Detecting the phonon spin in magnon-phonon conversion experiments

NASA Astrophysics Data System (ADS)

Holanda, J.; Maior, D. S.; Azevedo, A.; Rezende, S. M.

2018-05-01

Recent advances in the emerging field of magnon spintronics have stimulated renewed interest in phenomena involving the interaction between spin waves, the collective excitations of spins in magnetic materials that quantize as magnons, and the elastic waves that arise from excitations in the crystal lattice, which quantize as phonons. In magnetic insulators, owing to the magnetostrictive properties of materials, spin waves can become strongly coupled to elastic waves, forming magnetoelastic waves—a hybridized magnon-phonon excitation. While several aspects of this interaction have been subject to recent scrutiny, it remains unclear whether or not phonons can carry spin. Here we report experiments on a film of the ferrimagnetic insulator yttrium iron garnet under a non-uniform magnetic field demonstrating the conversion of coherent magnons generated by a microwave field into phonons that have spin. While it is well established that photons in circularly polarized light carry a spin, the spin of phonons has had little attention in the literature. By means of wavevector-resolved Brillouin light-scattering measurements, we show that the magnon-phonon conversion occurs with constant energy and varying linear momentum, and that the light scattered by the phonons is circularly polarized, thus demonstrating that the phonons have spin.

Assessment of Orbital-Optimized Third-Order Møller-Plesset Perturbation Theory and Its Spin-Component and Spin-Opposite Scaled Variants for Thermochemistry and Kinetics.

PubMed

Soydaş, Emine; Bozkaya, Uğur

2013-03-12

An assessment of the OMP3 method and its spin-component and spin-scaled variants for thermochemistry and kinetics is presented. For reaction energies of closed-shell systems, the CCSD, SCS-MP3, and SCS-OMP3 methods show better performances than other considered methods, and no significant improvement is observed due to orbital optimization. For barrier heights, OMP3 and SCS-OMP3 provide the lowest mean absolute deviations. The MP3 method yields considerably higher errors, and the spin scaling approaches do not help to improve upon MP3, but worsen it. For radical stabilization energies, the CCSD, OMP3, and SCS-OMP3 methods exhibit noticeably better performances than MP3 and its variants. Our results demonstrate that if the reference wave function suffers from a spin-contamination, then the MP3 methods dramatically fail. On the other hand, the OMP3 method and its variants can tolerate the spin-contamination in the reference wave function. For overall evaluation, we conclude that OMP3 is quite helpful, especially in electronically challenged systems, such as free radicals or transition states where spin contamination dramatically deteriorates the quality of the canonical MP3 and SCS-MP3 methods. Both OMP3 and CCSD methods scale as n(6), where n is the number of basis functions. However, the OMP3 method generally converges in much fewer iterations than CCSD. In practice, OMP3 is several times faster than CCSD in energy computations. Further, the stationary properties of OMP3 make it much more favorable than CCSD in the evaluation of analytic derivatives. For OMP3, the analytic gradient computations are much less expensive than CCSD. For the frequency computation, both methods require the evaluation of the perturbed amplitudes and orbitals. However, in the OMP3 case there is still a significant computational time savings due to simplifications in the analytic Hessian expression owing to the stationary property of OMP3. Hence, the OMP3 method emerges as a very useful tool for computational quantum chemistry.

Comparative analysis of local spin definitions.

PubMed

Herrmann, Carmen; Reiher, Markus; Hess, Bernd A

2005-01-15

This work provides a survey of the definition of electron spin as a local property and its dependence on several parameters in actual calculations. We analyze one-determinant wave functions constructed from Hartree-Fock and, in particular, from Kohn-Sham orbitals within the collinear approach to electron spin. The scalar total spin operators S2 and Sz are partitioned by projection operators, as introduced by Clark and Davidson, in order to obtain local spin operators SASB and SzA, respectively. To complement the work of Davidson and co-workers, we analyze some features of local spins which have not yet been discussed in sufficient depth. The dependence of local spin on the choice of basis set, density functional, and projector is studied. We also discuss the results of Sz partitioning and show that SzA values depend less on these parameters than SASB values. Furthermore, we demonstrate that for small organic test molecules, a partitioning of Sz with preorthogonalized Lowdin projectors yields nearly the same results as one obtains using atoms-in-molecules projectors. In addition, the physical significance of nonzero SASB values for closed-shell molecules is investigated. It is shown that due to this problem, SASB values are useful for calculations of relative spin values, but not for absolute local spins, where SzA values appear to be better suited.

Probing the antiferromagnetic long-range order with Glauber spin states

NASA Technical Reports Server (NTRS)

Cabrera, Guillermo G.

1994-01-01

It is well known that the ground state of low-dimensional antiferromagnets deviates from Neel states due to strong quantum fluctuations. Even in the presence of long-range order, those fluctuations produce a substantial reduction of the magnetic moment from its saturation value. Numerical simulations in anisotropic antiferromagnetic chains suggest that quantum fluctuations over Neel order appear in the form of localized reversal of pairs of neighboring spins. In this paper, we propose a coherent state representation for the ground state to describe the above situation. In the one-dimensional case, our wave function corresponds to a two-mode Glauber state, when the Neel state is used as a reference, while the boson fields are associated to coherent flip of spin pairs. The coherence manifests itself through the antiferromagnetic long-range order that survives the action of quantum fluctuations. The present representation is different from the standard zero-point spin wave state, and is asymptotically exact in the limit of strong anisotropy. The fermionic version of the theory, obtained through the Jordan-Wigner transformation, is also investigated.

Beating the Spin-down Limit on Gravitational Wave Emission from the Vela Pulsar

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Belletoile, A.; Belopolski, I.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chaibi, O.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Clara, F.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Das, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; del Prete, M.; Dent, T.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garofoli, J. A.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J. B.; Katsavounidis, E.; Katzman, W.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Kelner, M.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, H.; Kim, N.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, R.; Kwee, P.; Landry, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marandi, A.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Moesta, P.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishida, E.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parameswaran, A.; Pardi, S.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Podkaminer, J.; Poggiani, R.; Pöld, J.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C. R.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Redwine, K.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Salit, M.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schlamminger, S.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shihan Weerathunga, T.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Smith, R.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Stein, A. J.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Tseng, K.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration; Buchner, S.; Hotan, A.; Palfreyman, J.

2011-08-01

We present direct upper limits on continuous gravitational wave emission from the Vela pulsar using data from the Virgo detector's second science run. These upper limits have been obtained using three independent methods that assume the gravitational wave emission follows the radio timing. Two of the methods produce frequentist upper limits for an assumed known orientation of the star's spin axis and value of the wave polarization angle of, respectively, 1.9 × 10-24 and 2.2 × 10-24, with 95% confidence. The third method, under the same hypothesis, produces a Bayesian upper limit of 2.1 × 10-24, with 95% degree of belief. These limits are below the indirect spin-down limit of 3.3 × 10-24 for the Vela pulsar, defined by the energy loss rate inferred from observed decrease in Vela's spin frequency, and correspond to a limit on the star ellipticity of ~10-3. Slightly less stringent results, but still well below the spin-down limit, are obtained assuming the star's spin axis inclination and the wave polarization angles are unknown.

Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

PubMed Central

De, Anulekha; Mondal, Sucheta; Sahoo, Sourav; Barman, Saswati; Otani, Yoshichika; Mitra, Rajib Kumar

2018-01-01

Ferromagnetic antidot arrays have emerged as a system of tremendous interest due to their interesting spin configuration and dynamics as well as their potential applications in magnetic storage, memory, logic, communications and sensing devices. Here, we report experimental and numerical investigation of ultrafast magnetization dynamics in a new type of antidot lattice in the form of triangular-shaped Ni80Fe20 antidots arranged in a hexagonal array. Time-resolved magneto-optical Kerr effect and micromagnetic simulations have been exploited to study the magnetization precession and spin-wave modes of the antidot lattice with varying lattice constant and in-plane orientation of the bias-magnetic field. A remarkable variation in the spin-wave modes with the orientation of in-plane bias magnetic field is found to be associated with the conversion of extended spin-wave modes to quantized ones and vice versa. The lattice constant also influences this variation in spin-wave spectra and spin-wave mode profiles. These observations are important for potential applications of the antidot lattices with triangular holes in future magnonic and spintronic devices. PMID:29719763

Separated spin-up and spin-down quantum hydrodynamics of degenerated electrons: Spin-electron acoustic wave appearance.

PubMed

Andreev, Pavel A

2015-03-01

The quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different populations of states with different spin directions are included in the spin density (the magnetization). In this paper I derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence electrons with different projections of spins on the preferable direction are considered as two different species of particles. It is shown that the numbers of particles with different spin directions do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of the spins with the magnetic field. Terms of similar nature arise in the Euler equation. The z projection of the spin density is no longer an independent variable. It is proportional to the difference between the concentrations of the electrons with spin-up and the electrons with spin-down. The propagation of waves in the magnetized plasmas of degenerate electrons is considered. Two regimes for the ion dynamics, the motionless ions and the motion of the degenerate ions as the single species with no account of the spin dynamics, are considered. It is shown that this form of the QHD equations gives all solutions obtained from the traditional form of QHD equations with no distinction of spin-up and spin-down states. But it also reveals a soundlike solution called the spin-electron acoustic wave. Coincidence of most solutions is expected since this derivation was started with the same basic equation: the Pauli equation. Solutions arise due to the different Fermi pressures for the spin-up electrons and the spin-down electrons in the magnetic field. The results are applied to degenerate electron gas of paramagnetic and ferromagnetic metals in the external magnetic field. The dispersion of the spin-electron acoustic waves in the partially spin-polarized degenerate neutron matter are also considered.

Spin correlations and spin-wave excitations in Dirac-Weyl semimetals

NASA Astrophysics Data System (ADS)

Araki, Yasufumi; Nomura, Kentaro

We study correlations among magnetic dopants in three-dimensional Dirac and Weyl semimetals. Effective field theory for localized magnetic moments is derived by integrating out the itinerant electron degrees of freedom. We find that spin correlation in the spatial direction parallel to local magnetization is more rigid than that in the perpendicular direction, reflecting spin-momentum locking nature of the Dirac Hamiltonian. Such an anisotropy becomes stronger for Fermi level close to the Dirac points, due to Van Vleck paramagnetism triggered by spin-orbit coupling. One can expect topologically nontrivial spin textures under this anisotropy, such as a hedgehog around a single point, or a radial vortex around an axis, as well as a uniform ferromagnetic order. We further investigate the characteristics of spin waves in the ferromagnetic state. Spin-wave dispersion also shows a spatial anisotropy, which is less dispersed in the direction transverse to the magnetization than that in the longitudinal direction. The spin-wave dispersion anisotropy can be traced back to the rigidity and flexibility of spin correlations discussed above. This work was supported by Grant-in-Aid for Scientific Research (Grants No.15H05854, No.26107505, and No.26400308) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Experimental demonstration of the vertical spin existence in evanescent waves

NASA Astrophysics Data System (ADS)

Maksimyak, P. P.; Maksimyak, A. P.; Ivanskyi, D. I.

2018-01-01

Physical existence of the recently discovered vertical spin arising in an evanescent light wave due to the total internal reflection of a linearly polarized probing beam with azimuthal angle 45° is experimentally verified. Mechanical action, caused by optical force, associated with the extraordinary transverse component of the spin in evanescent wave is demonstrated. The motion of a birefringent plate in a direction controlled by simultaneous action of the canonical momentum and the transversal spin momentum is observed. The contribution of the canonical and spin momenta in determination of the trajectory of the resulting motion occur commensurable under exceptionally delicately determined experimental conditions.

Bound Magnon Dominance of the Magnetic Susceptibility of the One-Dimensional Heisenberg Spin One-Half Ferromagnet Cyclohexylammonium Trichlorocuprate

NASA Astrophysics Data System (ADS)

Haines, Donald Noble

1987-09-01

This study is an experimental investigation of the differential magnetic susceptibility of the spin one -half, one-dimensional, Ising-Heisenberg ferromagnet (S = 1over 2,1d,HIF). Recent theoretical work predicts the existence of magnon bound states in this model system, and that these bound spin wave states dominate its thermodynamic properties. Further, the theories indicate that classical linearized spin wave theory fails completely in such systems, and may also be intrinsically incorrect in certain higher dimensional systems. The purpose of this research is to confirm the existence of bound magnons in the S = 1over 2,1d,HIF for the nearly Heisenberg case, and demonstrate the dominance of the bound states over the spin wave states in determining thermodynamic behavior. A preliminary numerical study was performed to determine the ranges of magnetic field and temperature at which bound magnons might be expected to make a significant contribution to the magnetic susceptibility and specific heat of the S = 1over 2,1d,HIF. It was found that bound magnons dominate at low and high fields, and spin waves dominate at intermediate fields. For anisotropies less than 2% bound magnons dominate the low temperature regime for all fields. To test the theoretical predictions cyclohexylammonium trichlorocuprate(II) (CHAC) was chosen as a model S = 1over 2,1d,HIF compound for experimental study. The differential susceptibility of a powder sample of CHAC was measured as a function of temperature in fields of 0, 1, 2, and 3T. The temperature range for these studies was 4.2K to 40K. Susceptibility measurements were performed using an ac mutual inductance bridge which employs a SQUID (Superconducting Quantum Interference Device) as a null detector. The design, calibration, and operation of this instrument are described. Data from the experiments compare favorably with the theoretical predictions, confirming the existence of bound magnons in the nearly Heisenberg S = 1over 2,1d,HIF. Further, the experimental results clearly show that bound magnons are the dominant excitation determining the susceptibility for all fields and temperatures studied. Spin wave theory cannot describe the data for any values of the adjustable parameters.

Excitation of propagating magnetization waves by microstrip antennas

NASA Astrophysics Data System (ADS)

Dmitriev, V. F.; Kalinikos, B. A.

1988-11-01

We discuss the self-consistent theory of excitation of dipole-exchange magnetization waves by microstrip antennas in a metal-dielectric-ferrite-dielectric-metal stratified structure, magnetized under an arbitrary angle to the surface. Spin-wave Green's functions are derived, describing the response of the spin-system to a spatially inhomogeneous varying magnetic field. The radiative resistance of microstrip antenna is calculated. In this case the distribution of surface current density in the antenna is found on the basis of the analytic solution of a singular integral equation. The nature of the effect of metallic screens and redistributed surface current densities in the antenna on the frequency dependence of the resistive radiation is investigated. Approximate relations are obtained, convenient for practical calculations of radiative resistance of microstrip antennas both in a free and in a screened ferromagnetic film. The theoretical calculations are verified by data of experiments carried out on monocrystalline films of iron-yttrium garnet.

Nonreciprocal dispersion of spin waves in ferromagnetic thin films covered with a finite-conductivity metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mruczkiewicz, M.; Krawczyk, M.

2014-03-21

We study the effect of one-side metallization of a uniform ferromagnetic thin film on its spin-wave dispersion relation in the Damon–Eshbach geometry. Due to the finite conductivity of the metallic cover layer on the ferromagnetic film, the spin-wave dispersion relation may be nonreciprocal only in a limited wave-vector range. We provide an approximate analytical solution for the spin-wave frequency, discuss its validity, and compare it with numerical results. The dispersion is analyzed systematically by varying the parameters of the ferromagnetic film, the metal cover layer and the value of the external magnetic field. The conclusions drawn from this analysis allowmore » us to define a structure based on a 30 nm thick CoFeB film with an experimentally accessible nonreciprocal dispersion relation in a relatively wide wave-vector range.« less

Spin-wave utilization in a quantum computer

NASA Astrophysics Data System (ADS)

Khitun, A.; Ostroumov, R.; Wang, K. L.

2001-12-01

We propose a quantum computer scheme using spin waves for quantum-information exchange. We demonstrate that spin waves in the antiferromagnetic layer grown on silicon may be used to perform single-qubit unitary transformations together with two-qubit operations during the cycle of computation. The most attractive feature of the proposed scheme is the possibility of random access to any qubit and, consequently, the ability to recognize two qubit gates between any two distant qubits. Also, spin waves allow us to eliminate the use of a strong external magnetic field and microwave pulses. By estimate, the proposed scheme has as high as 104 ratio between quantum system coherence time and the time of a single computational step.

Dielectric magnetic microparticles as photomagnonic cavities: Enhancing the modulation of near-infrared light by spin waves

NASA Astrophysics Data System (ADS)

Almpanis, Evangelos

2018-05-01

The coupling between spin waves and optical Mie resonances inside a dielectric magnetic spherical particle, which acts simultaneously as a photonic and magnonic (photomagnonic) cavity, is investigated by means of numerical calculations accurate to arbitrary order in the magnetooptical coupling coefficient. Isolated dielectric magnetic particles with diameters of just a few microns support high-Q optical Mie resonances at near-infrared frequencies and localized spin waves, providing an ultrasmall and compact platform in the emerging field of cavity optomagnonics. Our results predict the occurrence of strong interaction effects, beyond the linear-response approximation, which lead to enhanced modulation of near-infrared light by spin waves through multimagnon absorption and emission mechanisms.

Direct observation and imaging of a spin-wave soliton with p-like symmetry

NASA Astrophysics Data System (ADS)

Bonetti, S.; Kukreja, R.; Chen, Z.; Macià, F.; Hernàndez, J. M.; Eklund, A.; Backes, D.; Frisch, J.; Katine, J.; Malm, G.; Urazhdin, S.; Kent, A. D.; Stöhr, J.; Ohldag, H.; Dürr, H. A.

2015-11-01

Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

Local spin density functional investigations of a manganite with perovskite-type derived structures

NASA Astrophysics Data System (ADS)

Matar, S. F.; Studer, F.; Siberchicot, B.; Subramanian, M. A.; Demazeau, G.; Etourneau, J.

1998-11-01

The electronic and magnetic structures of the perovskite CaMnO3 are self-consistently calculated assuming two crystal structures at the same formula unit volume within the local spin density functional theory and the augmented spherical wave (ASW) method. From the comparisons of energy differences between the different magnetic states the ground state configuration is an insulator with G-type ordering. This result together with the magnitudes of the magnetic moments are in agreement with experiment. The influence of mixing between Mn and O is found spin dependent from the analysis of the crystal orbital overlap population (COOP) which enable to describe the chemical bond. The calculations underline a feature of a half metallic ferromagnet which could be connected with the colossal magnetoresistance (CMR) property of related compounds.

Spin memory effect for compact binaries in the post-Newtonian approximation

NASA Astrophysics Data System (ADS)

Nichols, David A.

2017-04-01

The spin memory effect is a recently predicted relativistic phenomenon in asymptotically flat spacetimes that become nonradiative infinitely far in the past and future. Between these early and late times, the magnetic-parity part of the time integral of the gravitational-wave strain can undergo a nonzero change; this difference is the spin memory effect. Families of freely falling observers around an isolated source can measure this effect, in principle, and fluxes of angular momentum per unit solid angle (or changes in superspin charges) generate the effect. The spin memory effect had not been computed explicitly for astrophysical sources of gravitational waves, such as compact binaries. In this paper, we compute the spin memory in terms of a set of radiative multipole moments of the gravitational-wave strain. The result of this calculation allows us to establish the following results about the spin memory: (i) We find that the accumulation of the spin memory behaves in a qualitatively different way from that of the displacement memory effect for nonspinning, quasicircular compact binaries in the post-Newtonian approximation: the spin memory undergoes a large secular growth over the duration of the inspiral, whereas for the displacement effect this increase is small. (ii) The rate at which the spin memory grows is equivalent to a nonlinear, but nonoscillatory and nonhereditary effect in the gravitational waveform that had been previously calculated for nonspinning, quasicircular compact binaries. (iii) This rate of buildup of the spin memory could potentially be detected by future gravitational-wave detectors by carefully combining the measured waveforms from hundreds of gravitational-wave detections of compact binaries.

Eavesdropping on spin waves inside the domain-wall nanochannel via three-magnon processes

NASA Astrophysics Data System (ADS)

Zhang, Beining; Wang, Zhenyu; Cao, Yunshan; Yan, Peng; Wang, X. R.

2018-03-01

One recent breakthrough in the field of magnonics is the experimental realization of reconfigurable spin-wave nanochannels formed by a magnetic domain wall with a width of 10-100 nm [Wagner et al., Nat. Nano. 11, 432 (2016), 10.1038/nnano.2015.339]. This remarkable progress enables an energy-efficient spin-wave propagation with a well-defined wave vector along its propagating path inside the wall. In the mentioned experiment, a microfocus Brillouin light scattering spectroscopy was taken in a line-scans manner to measure the frequency of the bounded spin wave. Due to their localization nature, the confined spin waves can hardly be detected from outside the wall channel, which guarantees the information security to some extent. In this work, we theoretically propose a scheme to detect/eavesdrop on the spin waves inside the domain-wall nanochannel via nonlinear three-magnon processes. We send a spin wave (ωi,ki) in one magnetic domain to interact with the bounded mode (ωb,kb) in the wall, where kb is parallel with the domain-wall channel defined as the z ̂ axis. Two kinds of three-magnon processes, i.e., confluence and splitting, are expected to occur. The confluence process is conventional: conservation of energy and momentum parallel with the wall indicates a transmitted wave in the opposite domain with ω (k ) =ωi+ωb and (ki+kb-k ) .z ̂=0 , while the momentum perpendicular to the domain wall is not necessary to be conserved due to the nonuniform internal field near the wall. We predict a stimulated three-magnon splitting (or "magnon laser") effect: the presence of a bound magnon propagating along the domain wall channel assists the splitting of the incident wave into two modes, one is ω1=ωb,k1=kb identical to the bound mode in the channel, and the other one is ω2=ωi-ωb with (ki-kb-k2) .z ̂=0 propagating in the opposite magnetic domain. Micromagnetic simulations confirm our theoretical analysis. These results demonstrate that one is able to uniquely infer the spectrum of the spin wave in the domain-wall nanochannel once we know both the injection and the transmitted waves.

General theory of feedback control of a nuclear spin ensemble in quantum dots

NASA Astrophysics Data System (ADS)

Yang, Wen; Sham, L. J.

2013-12-01

We present a microscopic theory of the nonequilibrium nuclear spin dynamics driven by the electron and/or hole under continuous-wave pumping in a quantum dot. We show the correlated dynamics of the nuclear spin ensemble and the electron and/or hole under optical excitation as a quantum feedback loop and investigate the dynamics of the many nuclear spins as a nonlinear collective motion. This gives rise to three observable effects: (i) hysteresis, (ii) locking (avoidance) of the pump absorption strength to (from) the natural resonance, and (iii) suppression (amplification) of the fluctuation of weakly polarized nuclear spins, leading to prolonged (shortened) electron-spin coherence time. A single nonlinear feedback function is constructed which determines the different outcomes of the three effects listed above depending on the feedback being negative or positive. The general theory also helps to put in perspective the wide range of existing theories on the problem of a single electron spin in a nuclear spin bath.

Search for Gravitational Waves from Intermediate Mass Binary Black Holes

NASA Technical Reports Server (NTRS)

Blackburn, L.; Camp, J. B.; Cannizzo, J.; Stroeer, A. S.

2012-01-01

We present the results of a weakly modeled burst search for gravitational waves from mergers of non-spinning intermediate mass black holes (IMBH) in the total mass range 100-450 solar Mass and with the component mass ratios between 1:1 and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the IMBH mergers as a function of the component masses. In the most efficiently detected bin centered on 88 + 88 solar Mass , for non-spinning sources, the rate density upper limit is 0.13 per Mpc(exp 3) per Myr at the 90% confidence level.

Excitation of propagating spin waves by pure spin current

NASA Astrophysics Data System (ADS)

Demokritov, Sergej

Recently it was demonstrated that pure spin currents can be utilized to excite coherent magnetization dynamics, which enables development of novel magnetic nano-oscillators. Such oscillators do not require electric current flow through the active magnetic layer, which can help to reduce the Joule power dissipation and electromigration. In addition, this allows one to use insulating magnetic materials and provides an unprecedented geometric flexibility. The pure spin currents can be produced by using the spin-Hall effect (SHE). However, SHE devices have a number of shortcomings. In particular, efficient spin Hall materials exhibit a high resistivity, resulting in the shunting of the driving current through the active magnetic layer and a significant Joule heating. These shortcomings can be eliminated in devices that utilize spin current generated by the nonlocal spin-injection (NLSI) mechanism. Here we review our recent studies of excitation of magnetization dynamics and propagating spin waves by using NLSI. We show that NLSI devices exhibit highly-coherent dynamics resulting in the oscillation linewidth of a few MHz at room temperature. Thanks to the geometrical flexibility of the NLSI oscillators, one can utilize dipolar fields in magnetic nano-patterns to convert current-induced localized oscillations into propagating spin waves. The demonstrated systems exhibit efficient and controllable excitation and directional propagation of coherent spin waves characterized by a large decay length. The obtained results open new perspectives for the future-generation electronics using electron spin degree of freedom for transmission and processing of information on the nanoscale.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Woo-Pyo; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180–3590

The influence of electron spin-interaction on the propagation of the electrostatic space-charge quantum wave is investigated in a cylindrically bounded quantum plasma. The dispersion relation of the space-charge quantum electrostatic wave is derived including the influence of the electron spin-current in a cylindrical waveguide. It is found that the influence of electron spin-interaction enhances the wave frequency for large wave number regions. It is shown that the wave frequencies with higher-solution modes are always smaller than those with lower-solution modes in small wave number domains. In addition, it is found that the wave frequency increases with an increase of themore » radius of the plasma cylinder as well as the Fermi wave number. We discuss the effects due to the quantum and geometric on the variation of the dispersion properties of the space-charge plasma wave.« less

Asymptotic behavior of Nambu-Bethe-Salpeter wave functions for multiparticles in quantum field theories

NASA Astrophysics Data System (ADS)

Aoki, Sinya; Ishii, Noriyoshi; Doi, Takumi; Ikeda, Yoichi; Inoue, Takashi

2013-07-01

We derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than two particles in quantum field theories. To deal with n particles in the center-of-mass frame coherently, we introduce the Jacobi coordinates of n particles and then combine their 3(n-1) coordinates into the one spherical coordinate in D=3(n-1) dimensions. We parametrize the on-shell T matrix for n scalar particles at low energy using the unitarity constraint of the S matrix. We then express asymptotic behaviors of the NBS wave function for n particles at low energy in terms of parameters of the T matrix and show that the NBS wave function carries information of the T matrix such as phase shifts and mixing angles of the n-particle system in its own asymptotic behavior, so that the NBS wave function can be considered as the scattering wave of n particles in quantum mechanics. This property is one of the essential ingredients of the HAL QCD scheme to define “potential” from the NBS wave function in quantum field theories such as QCD. Our results, together with an extension to systems with spin 1/2 particles, justify the HAL QCD’s definition of potentials for three or more nucleons (or baryons) in terms of the NBS wave functions.

Pure detection of the acoustic spin pumping in Pt/YIG/PZT structures

NASA Astrophysics Data System (ADS)

Uchida, Ken-ichi; Qiu, Zhiyong; Kikkawa, Takashi; Saitoh, Eiji

2014-11-01

The acoustic spin pumping (ASP) stands for the generation of a spin voltage from sound waves in a ferromagnet/paramagnet junction. In this letter, we propose and demonstrate a method for pure detection of the ASP, which enables the separation of sound-wave-driven spin currents from the spin Seebeck effect due to the heating of a sample caused by a sound-wave injection. Our demonstration using a Pt/YIG/PZT sample shows that the ASP signal in this structure measured by a conventional method is considerably offset by the heating signal and that the pure ASP signal is one order of magnitude greater than that reported in the previous study.

Quantum gap and spin-wave excitations in the Kitaev model on a triangular lattice

NASA Astrophysics Data System (ADS)

Avella, Adolfo; Di Ciolo, Andrea; Jackeli, George

2018-05-01

We study the effects of quantum fluctuations on the dynamical generation of a gap and on the evolution of the spin-wave spectra of a frustrated magnet on a triangular lattice with bond-dependent Ising couplings, analog of the Kitaev honeycomb model. The quantum fluctuations lift the subextensive degeneracy of the classical ground-state manifold by a quantum order-by-disorder mechanism. Nearest-neighbor chains remain decoupled and the surviving discrete degeneracy of the ground state is protected by a hidden model symmetry. We show how the four-spin interaction, emergent from the fluctuations, generates a spin gap shifting the nodal lines of the linear spin-wave spectrum to finite energies.

Spin waves in planar quasicrystal of Penrose tiling

NASA Astrophysics Data System (ADS)

Rychły, J.; Mieszczak, S.; Kłos, J. W.

2018-03-01

We investigated two-dimensional magnonic structures which are the counterparts of photonic quasicrystals forming Penrose tiling. We considered the slab composed of Ni (or Py) disks embedded in Fe (or Co) matrix. The disks are arranged in quasiperiodic Penrose-like structure. The infinite quasicrystal was approximated by its rectangular section with periodic boundary conditions applied. This approach allowed us to use the plane wave method to find the frequency spectrum of eigenmodes for spin waves and their spatial profiles. The calculated integrated density of states shows more distinctive magnonic gaps for the structure composed of materials of high magnetic contrast (Ni and Fe) and relatively high filling fraction. This proves the impact of quasiperiodic long-range order on the spectrum of spin waves. We also investigated the localization of spin wave eingenmodes resulting from the quasiperiodicity of the structure.

Modulation of spin dynamics via voltage control of spin-lattice coupling in multiferroics

DOE PAGES

Zhu, Mingmin; Zhou, Ziyao; Peng, Bin; ...

2017-02-03

Our work aims at magnonics manipulation by the magnetoelectric coupling effect and is motivated by the most recent progresses in both magnonics (spin dynamics) and multiferroics fields. Here, voltage control of magnonics, particularly the surface spin waves, is achieved in La 0.7Sr 0.3MnO 3/0.7Pb(Mg 1/3Nb 2/3)O 3-0.3PbTiO 3 multiferroic heterostructures. With the electron spin resonance method, a large 135 Oe shift of surface spin wave resonance (≈7 times greater than conventional voltage-induced ferromagnetic resonance shift of 20 Oe) is determined. A model of the spin-lattice coupling effect, i.e., varying exchange stiffness due to voltage-induced anisotropic lattice changes, has been establishedmore » to explain experiment results with good agreement. In addition, an “on” and “off” spin wave state switch near the critical angle upon applying a voltage is created. The modulation of spin dynamics by spin-lattice coupling effect provides a platform for realizing energy-efficient, tunable magnonics devices.« less

Surprises from the spins: astrophysics and relativity with detections of spinning black-hole mergers

NASA Astrophysics Data System (ADS)

Gerosa, Davide

2018-03-01

Measurements of black-hole spins are of crucial importance to fulfill the promise of gravitational-wave astronomy. On the astrophysics side, spins are perhaps the cleanest indicator of black-hole evolutionary processes, thus providing a preferred way to discriminate how LIGO's black holes form. On the relativity side, spins are responsible for peculiar dynamical phenomena (from precessional modulations in the long inspiral to gravitational-wave recoils at merger) which encode precious information on the underlying astrophysical processes. I present some examples to explore this deep and fascinating interplay between spin dynamics (relativity) and environmental effects (astrophysics). Black-hole spins indeed hide remarkable surprises on both fronts: morphologies, resonances, constraints on supernova kicks, multiple merger generations and more... These findings were presented at 12th Edoardo Amaldi Conference on Gravitational Waves, held on July 9-14, 2017 in Pasadena, CA, USA.

Odd-frequency pairing in superconducting heterostructures .

NASA Astrophysics Data System (ADS)

Golubov, A. A.; Tanaka, Y.; Yokoyama, T.; Asano, Y.

2007-03-01

We present a general theory of the proximity effect in junctions between unconventional superconductors and diffusive normal metals (DN) or ferromagnets (DF). We consider all possible symmetry classes in a superconductor allowed by the Pauli principle: even-frequency spin-singlet even-parity state, even-frequency spin-triplet odd-parity state, odd-frequency spin-triplet even-parity state and odd-frequency spin-singlet odd-parity state. For each of the above states, symmetry and spectral properties of the induced pair amplitude in the DN (DF) are determined. The cases of junctions with spin-singlet s- and d-wave superconductors and spin-triplet p-wave superconductors are adressed in detail. We discuss the interplay between the proximity effect and midgap Andreev bound states arising at interfaces in unconventional (d- or p-wave) junctions. The most striking property is the odd-frequency symmetry of the pairing amplitude induced in DN (DF) in contacts with p-wave superconductors. This leads to zero-energy singularity in the density of states and to anomalous screening of an external magnetic field. Peculiarities of Josephson effect in d- or p-wave junctions are discussed. Experiments are suggested to detect an order parameter symmetry using heterostructures with unconventional superconductors.

Direct observation and imaging of a spin-wave soliton with p-like symmetry

DOE PAGES

Bonetti, S.; Kukreja, R.; Chen, Z.; ...

2015-11-16

Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Moreover, micromagnetic simulations explain the measurements and reveal that the symmetrymore » of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.« less

A reconfigurable waveguide for energy-efficient transmission and local manipulation of information in a nanomagnetic device

NASA Astrophysics Data System (ADS)

Haldar, Arabinda; Kumar, Dheeraj; Adeyeye, Adekunle Olusola

2016-05-01

Spin-wave-based devices promise to usher in an era of low-power computing where information is carried by the precession of the electrons' spin instead of dissipative translation of their charge. This potential is, however, undermined by the need for a bias magnetic field, which must remain powered on to maintain an anisotropic device characteristic. Here, we propose a reconfigurable waveguide design that can transmit and locally manipulate spin waves without the need for any external bias field once initialized. We experimentally demonstrate the transmission of spin waves in straight as well as curved waveguides without a bias field, which has been elusive so far. Furthermore, we experimentally show a binary gating of the spin-wave signal by controlled switching of the magnetization, locally, in the waveguide. The results have potential implications in high-density integration and energy-efficient operation of nanomagnetic devices at room temperature.

Temperature dependence of current polarization in Ni80Fe20 by spin wave Doppler measurements

NASA Astrophysics Data System (ADS)

Zhu, Meng; Dennis, Cindi; McMichael, Robert

2010-03-01

The temperature dependence of current polarization in ferromagnetic metals will be important for operation of spin-torque switched memories and domain wall devices in a wide temperature range. Here, we use the spin wave Doppler technique[1] to measure the temperature dependence of both the magnetization drift velocity v(T) and the current polarization P(T) in Ni80Fe20. We obtain these values from current-dependent shifts of the spin wave transmission resonance frequency for fixed-wavelength spin waves in current-carrying wires. For current densities of 10^11 A/m^2, we obtain v(T) decreasing from 4.8 ±0.3 m/s to 4.1 ±0.1 m/s and P(T) dropping from 0.75±0.05 to 0.58±0.02 over a temperature range from 80 K to 340 K. [1] V. Vlaminck et al. Science 322, 410 (2008);

Nanopatterned reconfigurable spin-textures for magnonics

NASA Astrophysics Data System (ADS)

Albisetti, E.; Petti, D.; Pancaldi, M.; Madami, M.; Tacchi, S.; Curtis, J.; King, W. P.; Papp, A.; Csaba, G.; Porod, W.; Vavassori, P.; Riedo, E.; Bertacco, R.

The control of spin-waves holds the promise to enable energy-efficient information transport and wave-based computing. Conventionally, the engineering of spin-waves is achieved via physically patterning magnetic structures such as magnonic crystals and micro-nanowires. We demonstrate a new concept for creating reconfigurable magnonic nanostructures, by crafting at the nanoscale the magnetic anisotropy landscape of a ferromagnet exchange-coupled to an antiferromagnet. By performing a highly localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are patterned without modifying the film chemistry and topography. We demonstrate that, in such structures, the spin-wave excitation and propagation can be spatially controlled at remanence, and can be tuned by external magnetic fields. This opens the way to the use of nanopatterned spin-textures, such as domains and domain walls, for exciting and manipulating magnons in reconfigurable nanocircuits. Partially funded by the EC through project SWING (no. 705326).

Highly retrievable spin-wave-photon entanglement source.

PubMed

Yang, Sheng-Jun; Wang, Xu-Jie; Li, Jun; Rui, Jun; Bao, Xiao-Hui; Pan, Jian-Wei

2015-05-29

Entanglement between a single photon and a quantum memory forms the building blocks for a quantum repeater and quantum network. Previous entanglement sources are typically with low retrieval efficiency, which limits future larger-scale applications. Here, we report a source of highly retrievable spin-wave-photon entanglement. Polarization entanglement is created through interaction of a single photon with an ensemble of atoms inside a low-finesse ring cavity. The cavity is engineered to be resonant for dual spin-wave modes, which thus enables efficient retrieval of the spin-wave qubit. An intrinsic retrieval efficiency up to 76(4)% has been observed. Such a highly retrievable atom-photon entanglement source will be very useful in future larger-scale quantum repeater and quantum network applications.

Point form relativistic quantum mechanics and relativistic SU(6)

NASA Technical Reports Server (NTRS)

Klink, W. H.

1993-01-01

The point form is used as a framework for formulating a relativistic quantum mechanics, with the mass operator carrying the interactions of underlying constituents. A symplectic Lie algebra of mass operators is introduced from which a relativistic harmonic oscillator mass operator is formed. Mass splittings within the degenerate harmonic oscillator levels arise from relativistically invariant spin-spin, spin-orbit, and tensor mass operators. Internal flavor (and color) symmetries are introduced which make it possible to formulate a relativistic SU(6) model of baryons (and mesons). Careful attention is paid to the permutation symmetry properties of the hadronic wave functions, which are written as polynomials in Bargmann spaces.

s± pairing near a Lifshitz transition

DOE PAGES

Mishra, Vivek; Scalapino, Douglas J.; Maier, Thomas A.

2016-08-26

Observations of robust superconductivity in some of the iron based superconductors in the vicinity of a Lifshitz point where a spin density wave instability is suppressed as the hole band drops below the Fermi energy raise questions for spin-fluctuation theories. In this paper we discuss spin-fluctuation pairing for a bilayer Hubbard model, which goes through such a Lifshitz transition. Our results show s± pairing with a transition temperature that peaks beyond the Lifshitz point and a gap function that has essentially the same magnitude but opposite sign on the incipient hole band as it does on the electron band thatmore » has a Fermi surface.« less

Large Spin-Wave Bullet in a Ferrimagnetic Insulator Driven by the Spin Hall Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jungfleisch, M. B.; Zhang, W.; Sklenar, J.

2016-02-01

Due to its transverse nature, spin Hall effects (SHE) provide the possibility to excite and detect spin currents and magnetization dynamics even in magnetic insulators. Magnetic insulators are outstanding materials for the investigation of nonlinear phenomena and for novel low power spintronics applications because of their extremely low Gilbert damping. Here, we report on the direct imaging of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the ferrimagnetic insulator Y 3Fe 5O 12 based on the excitation and detection by SHEs. The driven spin dynamics in Y 3Fe 5O 12 is directly imaged by spatially-resolved microfocused Brillouin light scattering (BLS) spectroscopy.more » Previously, ST-FMR experiments assumed a uniform precession across the sample, which is not valid in our measurements. A strong spin-wave localization in the center of the sample is observed indicating the formation of a nonlinear, self-localized spin-wave `bullet'.« less

Hall viscosity of hierarchical quantum Hall states

NASA Astrophysics Data System (ADS)

Fremling, M.; Hansson, T. H.; Suorsa, J.

2014-03-01

Using methods based on conformal field theory, we construct model wave functions on a torus with arbitrary flat metric for all chiral states in the abelian quantum Hall hierarchy. These functions have no variational parameters, and they transform under the modular group in the same way as the multicomponent generalizations of the Laughlin wave functions. Assuming the absence of Berry phases upon adiabatic variations of the modular parameter τ, we calculate the quantum Hall viscosity and find it to be in agreement with the formula, given by Read, which relates the viscosity to the average orbital spin of the electrons. For the filling factor ν =2/5 Jain state, which is at the second level in the hierarchy, we compare our model wave function with the numerically obtained ground state of the Coulomb interaction Hamiltonian in the lowest Landau level, and find very good agreement in a large region of the complex τ plane. For the same example, we also numerically compute the Hall viscosity and find good agreement with the analytical result for both the model wave function and the numerically obtained Coulomb wave function. We argue that this supports the notion of a generalized plasma analogy that would ensure that wave functions obtained using the conformal field theory methods do not acquire Berry phases upon adiabatic evolution.

Structural instability in polyacene: A projector quantum Monte Carlo study

NASA Astrophysics Data System (ADS)

Srinivasan, Bhargavi; Ramasesha, S.

1998-04-01

We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls' instability in a system marginally away from one dimension. We employ the projector quantum Monte Carlo method to obtain ground-state estimates of the energy and various correlation functions. We find strong similarities between polyacene and polyacetylene which can be rationalized from the real-space valence-bond arguments of Mazumdar and Dixit. Electron correlations tend to enhance the Peierls' instability in polyacene. This enhancement appears to attain a maximum at U/t~3.0, and the maximum shifts to larger values when the alternation parameter is increased. The system shows no tendency to destroy the imposed bond-alternation pattern, as evidenced by the bond-bond correlations. The cis distortion is seen to be favored over the trans distortion. The spin-spin correlations show that undistorted polyacene is susceptible to a spin-density-wave distortion for large interaction strength. The charge-charge correlations indicate the absence of a charge-density-wave distortion for the parameters studied.

Spin and Pseudospin Symmetries of Hellmann Potential with Three Tensor Interactions Using Nikiforov-Uvarov Method

NASA Astrophysics Data System (ADS)

Akpan, N. Ikot; Hassan, Hassanabadi; Tamunoimi, M. Abbey

2015-12-01

The Dirac equation with Hellmann potential is presented in the presence of Coulomb-like tensor (CLT), Yukawa-like tensor (YLT), and Hulthen-type tensor (HLT) interactions by using Nikiforov-Uvarov method. The bound state energy spectra and the radial wave functions are obtained approximately within the framework of spin and pseudospin symmetries limit. We have also reported some numerical results and figures to show the effects of the tensor interactions. Special cases of the potential are also discussed.

Switching dynamics of the spin density wave in superconducting CeCoIn 5

DOE PAGES

Kim, Duk Y.; Lin, Shi-Zeng; Bauer, Eric D.; ...

2017-06-21

The ordering wave vector Q of a spin density wave (SDW), stabilized within the superconducting state of CeCoIn 5 in a high magnetic field, has been shown to be hypersensitive to the direction of the field. Q can be switched from a nodal direction of the d-wave superconducting order parameter to a perpendicular node by rotating the in-plane magnetic field through the antinodal direction within a fraction of a degree. In this paper, we address the dynamics of the switching of Q. We use a free-energy functional based on the magnetization density, which describes the condensation of magnetic fluctuations ofmore » nodal quasiparticles, and show that the switching process includes closing of the SDW gap at one Q and then reopening the SDW gap at another Q perpendicular to the first one. The magnetic field couples to Q through the spin-orbit interaction. Our calculations show that the width of the hysteretic region of switching depends linearly on the deviation of magnetic field from the critical field associated with the SDW transition, consistent with our thermal conductivity measurements. Finally, the agreement between theory and experiment supports our scenario of the hypersensitivity of the Q phase on the direction of magnetic field, as well as the magnon condensation as the origin of the SDW phase in CeCoIn 5.« less

Structure of the first order reduced density matrix in three electron systems: A generalized Pauli constraints assisted study.

PubMed

Theophilou, Iris; Lathiotakis, Nektarios N; Helbig, Nicole

2018-03-21

We investigate the structure of the one-body reduced density matrix of three electron systems, i.e., doublet and quadruplet spin configurations, corresponding to the smallest interacting system with an open-shell ground state. To this end, we use configuration interaction (CI) expansions of the exact wave function in Slater determinants built from natural orbitals in a finite dimensional Hilbert space. With the exception of maximally polarized systems, the natural orbitals of spin eigenstates are generally spin dependent, i.e., the spatial parts of the up and down natural orbitals form two different sets. A measure to quantify this spin dependence is introduced and it is shown that it varies by several orders of magnitude depending on the system. We also study the ordering issue of the spin-dependent occupation numbers which has practical implications in reduced density matrix functional theory minimization schemes, when generalized Pauli constraints (GPCs) are imposed and in the form of the CI expansion in terms of the natural orbitals. Finally, we discuss the aforementioned CI expansion when there are GPCs that are almost "pinned."

Gauge invariant gluon spin operator for spinless nonlinear wave solutions

NASA Astrophysics Data System (ADS)

Lee, Bum-Hoon; Kim, Youngman; Pak, D. G.; Tsukioka, Takuya; Zhang, P. M.

2017-04-01

We consider nonlinear wave type solutions with intrinsic mass scale parameter and zero spin in a pure SU(2) quantum chromodynamics (QCD). A new stationary solution which can be treated as a system of static Wu-Yang monopole dressed in off-diagonal gluon field is proposed. A remarkable feature of such a solution is that it possesses a finite energy density everywhere. All considered nonlinear wave type solutions have common features: presence of the mass scale parameter, nonvanishing projection of the color fields along the propagation direction and zero spin. The last property requires revision of the gauge invariant definition of the spin density operator which is supposed to produce spin one states for the massless vector gluon field. We construct a gauge invariant definition of the classical gluon spin density operator which is unique and Lorentz frame independent.

High-Frequency EPR and ENDOR Spectroscopy on Semiconductor Quantum Dots.

PubMed

Baranov, Pavel G; Orlinskii, Sergei B; de Mello Donegá, Celso; Schmidt, Jan

2010-10-01

It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast to optical methods, they allow the identification of the dopants and provide information about the spatial distribution of the electronic wave function. This latter aspect is particularly attractive because it allows for a quantitative measurement of the effect of confinement on the shape and properties of the wave function. In this contribution EPR and ENDOR results are presented on doped ZnO QDs. Shallow donors (SDs), related to interstitial Li and Na and substitutional Al atoms, have been identified in this material by pulsed high-frequency EPR and ENDOR spectroscopy. The shallow character of the wave function of the donors is evidenced by the multitude of ENDOR transitions of the (67)Zn nuclear spins and by the hyperfine interaction of the (7)Li, (23)Na and (27)Al nuclear spins that are much smaller than for atomic lithium, sodium and aluminium. The EPR signal of an exchange-coupled pair consisting of a shallow donor and a deep Na-related acceptor has been identified in ZnO nanocrystals with radii smaller than 1.5 nm. From ENDOR experiments it is concluded that the deep Na-related acceptor is located at the interface of the ZnO core and the Zn(OH)(2) capping layer, while the shallow donor is in the ZnO core. The spatial distribution of the electronic wave function of a shallow donor in ZnO semiconductor QDs has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine interactions as monitored by ENDOR spectroscopy quantitatively reveal the transition from semiconductor to molecular properties upon reduction of the size of the nanoparticles. In addition, the effect of confinement on the g-factor of SDs in ZnO as well as in CdS QDs is observed. Finally, it is shown that an almost complete dynamic nuclear polarization (DNP) of the (67)Zn nuclear spins in the core of ZnO QDs and of the (1)H nuclear spins in the Zn(OH)(2) capping layer can be obtained. This DNP is achieved by saturating the EPR transition of SDs present in the QDs with resonant high-frequency microwaves at low temperatures. This nuclear polarization manifests itself as a hole and an antihole in the EPR absorption line of the SD in the QDs and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with nuclear magnetic resonance techniques.

High-Frequency EPR and ENDOR Spectroscopy on Semiconductor Quantum Dots

PubMed Central

Baranov, Pavel G.; de Mello Donegá, Celso; Schmidt, Jan

2010-01-01

It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast to optical methods, they allow the identification of the dopants and provide information about the spatial distribution of the electronic wave function. This latter aspect is particularly attractive because it allows for a quantitative measurement of the effect of confinement on the shape and properties of the wave function. In this contribution EPR and ENDOR results are presented on doped ZnO QDs. Shallow donors (SDs), related to interstitial Li and Na and substitutional Al atoms, have been identified in this material by pulsed high-frequency EPR and ENDOR spectroscopy. The shallow character of the wave function of the donors is evidenced by the multitude of ENDOR transitions of the 67Zn nuclear spins and by the hyperfine interaction of the 7Li, 23Na and 27Al nuclear spins that are much smaller than for atomic lithium, sodium and aluminium. The EPR signal of an exchange-coupled pair consisting of a shallow donor and a deep Na-related acceptor has been identified in ZnO nanocrystals with radii smaller than 1.5 nm. From ENDOR experiments it is concluded that the deep Na-related acceptor is located at the interface of the ZnO core and the Zn(OH)2 capping layer, while the shallow donor is in the ZnO core. The spatial distribution of the electronic wave function of a shallow donor in ZnO semiconductor QDs has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine interactions as monitored by ENDOR spectroscopy quantitatively reveal the transition from semiconductor to molecular properties upon reduction of the size of the nanoparticles. In addition, the effect of confinement on the g-factor of SDs in ZnO as well as in CdS QDs is observed. Finally, it is shown that an almost complete dynamic nuclear polarization (DNP) of the 67Zn nuclear spins in the core of ZnO QDs and of the 1H nuclear spins in the Zn(OH)2 capping layer can be obtained. This DNP is achieved by saturating the EPR transition of SDs present in the QDs with resonant high-frequency microwaves at low temperatures. This nuclear polarization manifests itself as a hole and an antihole in the EPR absorption line of the SD in the QDs and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with nuclear magnetic resonance techniques. PMID:20936163

Localized parallel parametric generation of spin waves in a Ni{sub 81}Fe{sub 19} waveguide by spatial variation of the pumping field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brächer, T.; Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, D-67663 Kaiserslautern; Pirro, P.

2014-03-03

We present the experimental observation of localized parallel parametric generation of spin waves in a transversally in-plane magnetized Ni{sub 81}Fe{sub 19} magnonic waveguide. The localization is realized by combining the threshold character of parametric generation with a spatially confined enhancement of the amplifying microwave field. The latter is achieved by modulating the width of the microstrip transmission line which is used to provide the pumping field. By employing microfocussed Brillouin light scattering spectroscopy, we analyze the spatial distribution of the generated spin waves and compare it with numerical calculations of the field distribution along the Ni{sub 81}Fe{sub 19} waveguide. Thismore » provides a local spin-wave excitation in transversally in-plane magnetized waveguides for a wide wave-vector range which is not restricted by the size of the generation area.« less

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru

2015-06-15

We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular tomore » an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.« less

Pair correlations in low-lying T =0 states of odd-odd nuclei with six nucleons

NASA Astrophysics Data System (ADS)

Fu, G. J.; Zhao, Y. M.; Arima, A.

2018-02-01

In this paper, we study pair correlations in low-lying T =0 states for two typical cases of odd-odd N =Z nuclei. The first case is six nucleons in a single j =9 /2 shell, for which we study the S -broken-pair approximation, the isoscalar spin-1 pair condensation, and the isoscalar spin-aligned pair condensation, with schematic interactions. In the second case, we study pair approximations and correlation energies for 22Na, 34Cl, 46V, 62Ga, and 94Ag in multi-j shells with effective interactions. A few T =0 states are found to be well represented by isoscalar nucleon pairs. The isoscalar spin-aligned pairs play an important role for the yrast T =0 states with I ˜2 j and I ˜Imax in 22Na, 46V, and 94Ag. The overlap between the isoscalar J =1 pair wave function and the shell-model wave function is around 0.5 for the I =1 ,3 states of 34Cl and the I =1 state of 94Ag. The I =9 state of 62Ga is very well described by the isoscalar J =3 pair condensation. The broken-pair approximation (which is similar to the 2-quasiparticle excitation of the isovector pair condensation) is appropriate for quite few states, such as the I =1 -3 states of 34Cl and the I =5 state of 62Ga. The correlation energies are presented in this paper. It is noted that the picture based on nucleon-pair wave functions is not always in agreement with the picture based on correlation energies.

Photoinduced dynamics to photoluminescence in Ln3+ (Ln = Ce, Pr) doped β-NaYF4 nanocrystals computed in basis of non-collinear spin DFT with spin-orbit coupling

NASA Astrophysics Data System (ADS)

Han, Yulun; Vogel, Dayton J.; Inerbaev, Talgat M.; May, P. Stanley; Berry, Mary T.; Kilin, Dmitri S.

2018-03-01

In this work, non-collinear spin DFT + U approaches with spin-orbit coupling (SOC) are applied to Ln3+ doped β-NaYF4 (Ln = Ce, Pr) nanocrystals in Vienna ab initio Simulation Package taking into account unpaired spin configurations using the Perdew-Burke-Ernzerhof functional in a plane wave basis set. The calculated absorption spectra from non-collinear spin DFT + U approaches are compared with that from spin-polarised DFT + U approaches. The spectral difference indicates the importance of spin-flip transitions of Ln3+ ions. Suite of codes for nonadiabatic dynamics has been developed for 2-component spinor orbitals. On-the-fly nonadiabatic coupling calculations provide transition probabilities facilitated by nuclear motion. Relaxation rates of electrons and holes are calculated using Redfield theory in the reduced density matrix formalism cast in the basis of non-collinear spin DFT + U with SOC. The emission spectra are calculated using the time-integrated method along the excited state trajectories based on nonadiabatic couplings.

Spin dynamics of possible density wave states in the pseudogap phase of high-temperature superconductors

NASA Astrophysics Data System (ADS)

Hsu, Chen-Hsuan; Wang, Zhiqiang; Chakravarty, Sudip

2012-12-01

In a recent inelastic neutron scattering experiment in the pseudogap state of the high-temperature superconductor YBa2Cu3O6.6, an unusual “vertical” dispersion of the spin excitations with a large in-plane anisotropy was observed. In this paper, we discuss in detail the spin susceptibility of the singlet d-density wave, the triplet d-density wave as well as the more common spin density wave orders with hopping anisotropies. From numerical calculations within the framework of random phase approximation, we find nearly vertical dispersion relations for spin excitations with anisotropic incommensurability at low energy ω≤90meV, which are reminiscent of the experiments. At very high energy ω≥165meV, we also find energy-dependent incommensurability. Although there are some important differences between the three cases, unpolarized neutron measurements cannot discriminate between these alternate possibilities; the vertical dispersion, however, is a distinct feature of all three density wave states in contrast to the superconducting state, which shows an hour-glass shape dispersion.

Lorentz-boosted evanescent waves

NASA Astrophysics Data System (ADS)

Bliokh, Konstantin Y.

2018-06-01

Polarization, spin, and helicity are important properties of electromagnetic waves. It is commonly believed that helicity is invariant under the Lorentz transformations. This is indeed so for plane waves and their localized superpositions. However, this is not the case for evanescent waves, which are well-defined only in a half-space, and are characterized by complex wave vectors. Here we describe transformations of evanescent electromagnetic waves and their polarization/spin/helicity properties under the Lorentz boosts along the three spatial directions.

Theory of magnetoelastic resonance in a monoaxial chiral helimagnet

NASA Astrophysics Data System (ADS)

Tereshchenko, A. A.; Ovchinnikov, A. S.; Proskurin, Igor; Sinitsyn, E. V.; Kishine, Jun-ichiro

2018-05-01

We study magnetoelastic resonance phenomena in a monoaxial chiral helimagnet belonging to the hexagonal crystal class. By computing the spectrum of a coupled elastic wave and spin wave, it is demonstrated how hybridization occurs depending on their chirality. Specific features of the magnetoelastic resonance are discussed for the conical phase and the soliton lattice phase stabilized in the monoaxial chiral helimagnet. The former phase exhibits appreciable nonreciprocity of the spectrum, and the latter is characterized by a multiresonance behavior. We propose that the nonreciprocal spin wave around the forced-ferromagnetic state has potential capability to convert the linearly polarized elastic wave to a circularly polarized one with the chirality opposite to the spin-wave chirality.

Topological helical edge states in water waves over a topographical bottom

NASA Astrophysics Data System (ADS)

Wu, Shiqiao; Wu, Ying; Mei, Jun

2018-02-01

We present the discovery of topologically protected helical edge states in water wave systems, which are realized in water wave propagating over a topographical bottom whose height is modulated periodically in a two-dimensional triangular pattern. We develop an effective Hamiltonian to characterize the dispersion relation and use spin Chern numbers to classify the topology. Through full-wave simulations we unambiguously demonstrate the robustness of the helical edge states which are immune to defects and disorders so that the backscattering loss is significantly reduced. A spin splitter is designed for water wave systems, where helical edge states with different spin orientations are spatially separated with each other, and potential applications are discussed.

Phase transition and field effect topological quantum transistor made of monolayer MoS2

NASA Astrophysics Data System (ADS)

Simchi, H.; Simchi, M.; Fardmanesh, M.; Peeters, F. M.

2018-06-01

We study topological phase transitions and topological quantum field effect transistor in monolayer molybdenum disulfide (MoS2) using a two-band Hamiltonian model. Without considering the quadratic (q 2) diagonal term in the Hamiltonian, we show that the phase diagram includes quantum anomalous Hall effect, quantum spin Hall effect, and spin quantum anomalous Hall effect regions such that the topological Kirchhoff law is satisfied in the plane. By considering the q 2 diagonal term and including one valley, it is shown that MoS2 has a non-trivial topology, and the valley Chern number is non-zero for each spin. We show that the wave function is (is not) localized at the edges when the q 2 diagonal term is added (deleted) to (from) the spin-valley Dirac mass equation. We calculate the quantum conductance of zigzag MoS2 nanoribbons by using the nonequilibrium Green function method and show how this device works as a field effect topological quantum transistor.

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions

NASA Astrophysics Data System (ADS)

Jerke, Jonathan; Poirier, Bill

2018-03-01

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy—i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted—as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions.

PubMed

Jerke, Jonathan; Poirier, Bill

2018-03-14

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy-i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted-as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Tunable Snell's law for spin waves in heterochiral magnetic films

NASA Astrophysics Data System (ADS)

Mulkers, Jeroen; Van Waeyenberge, Bartel; Milošević, Milorad V.

2018-03-01

Thin ferromagnetic films with an interfacially induced DMI exhibit nontrivial asymmetric dispersion relations that lead to unique and useful magnonic properties. Here we derive an analytical expression for the magnon propagation angle within the micromagnetic framework and show how the dispersion relation can be approximated with a comprehensible geometrical interpretation in the k space of the propagation of spin waves. We further explore the refraction of spin waves at DMI interfaces in heterochiral magnetic films, after deriving a generalized Snell's law tunable by an in-plane magnetic field, that yields analytical expressions for critical incident angles. The found asymmetric Brewster angles at interfaces of regions with different DMI strengths, adjustable by magnetic field, support the conclusion that heterochiral ferromagnetic structures are an ideal platform for versatile spin-wave guides.

FMR-driven spin pumping in Y3Fe5O12-based structures

NASA Astrophysics Data System (ADS)

Yang, Fengyuan; Hammel, P. Chris

2018-06-01

Ferromagnetic resonance driven spin pumping, a topic of steadily increasing interest since its emergence over two decades ago, remains one of the most exciting research fields in condensed matter physics. Among the many materials that have been explored for spin pumping, yttrium iron garnet (YIG) is one of the most extensively studied because of its exceptionally low magnetic damping and insulating nature. There is a great amount of literature in the spin pumping and related research fields, too broad for this review to cover. In this Topical Review, we focus on the YIG-based spin pumping results carried out by our groups, including: the mechanism and technical details of our off-axis sputtering technique for the growth of single-crystalline YIG epitaxial films with a high degree ordering, experimental evidence for the high quality of the YIG films, spin pumping results from YIG into various transition metals and their heterostructures, dynamic spin transport in YIG/antiferromagnet hybrid structures, intralayer spin pumping by localized spin wave modes confined by a micromagnetic probe, dynamic spin coupling between YIG and nitrogen-vacancy centers in diamond, parametric spin pumping from high-wavevector spin waves in YIG, and localized spin wave mode behavior in broadly tunable spatially complex magnetic configurations. These results build on the power and versatility of YIG spin pumping to improve our understanding of spin dynamics, spin currents, spin Hall physics, spin–orbit coupling, dynamic magnetic coupling, and the relationship between these phenomena in a broad range of materials, geometries, and settings.

NMR studies of spin dynamics in cuprates

NASA Astrophysics Data System (ADS)

Takigawa, M.; Mitzi, D. B.

1994-04-01

We report recent NMR results in cuprates. The oxygen Knight shift and the Cu nuclear spin-lattice relaxation rate in Bi2.1Sr1.94Ca0.88Cu2.07O8+δ single crystals revealed a gapless superconducting state, which can be most naturally explained by a d-wave pairing state and the intrinsic disorder in this material. The Cu nuclear spin-spin relaxation rate in underdoped YBa2Cu3O6.63 shows distinct temperature dependence from the spin-lattice relaxation rate, providing direct evidence for a pseudo spin-gap near the antiferromagnetic wave vector.

Non-Equilibrium Dynamics of Fermi Gases Near A Scattering Resonance

NASA Astrophysics Data System (ADS)

Trotzky, S.; Luciuk, C.; Smale, S.; Beattie, S.; Taylor, E.; Enss, T.; Zhang, Shizhong; Thywissen, J. H.

2015-05-01

We present recent dynamic measurements of fermionic potassium (40K) near Fano-Feshbach scattering resonances. In our experiments, we start with a weakly or non-interacting Fermi gas and initiate strong interactions on a timescale that is fast compared to the equilibration mechanisms in the system quasi-instantaneous quench. Equally fast measurements allow us to follow the non-equilibrium many-body dynamics. First, we discuss time-resolved radio-frequency (rf) spectroscopy, and its use to probe the evolution of the short-range part of the many-body wave function - i.e., the contact. Second, we discuss spin-echo measurements that reveal the nature of transverse spin transport. Most recently, we have studied a Fermi gas with repulsive interactions in the metastable upper branch of the energy spectrum near a s-wave scattering resonance.

Time-resolved nonlinear optics in strongly correlated insulators

NASA Astrophysics Data System (ADS)

Dodge, J. Steven

2000-03-01

Transition metal oxides form the basis for much of our understanding of Mott insulators, and have enjoyed a renaissance of interest since the discovery of high temperature superconductivity in the cuprates. They are characterized by complex interactions among spin, lattice, orbital and charge degrees of freedom, which lead to dynamical behavior on time scales ranging from femtoseconds to microseconds. We have applied time resolved nonlinear optical spectroscopy to probe these dynamics. In one well-studied antiferromagnetic insulator, Cr_2O_3, we observed spin-wave dynamics on a picosecond time scale by performing pump-probe spectroscopy of the exciton-magnon transition(J. S. Dodge, et al.), Phys. Rev. Lett. 83, 4650 (1999).. At excitation densities ~ 10-3/Cr, a lineshape associated with the exciton-magnon absorption appears in the pump-probe spectrum. We assign this nonlinearity to a time-dependent renormalization of the magnon band structure, which in turn modifies the lineshape of the exciton-magnon transition. At long time delays, this assignment agrees semiquantitatively with calculations based on spin-wave theory. However, the initial population at the zone-boundary induces surprisingly little renormalization effect, indicating that spin-wave theory is insufficient to describe our observations in this regime. The renormalization lineshape grows on a time scale of ~ 50 ps, which we associate with the decay of the photoexcited, nonequilibrium population of zone-boundary spin-waves into a thermalized population of zone-center spin-waves. We have also performed a study of the linear and nonlinear optical properties of Sr_2CuO_2Cl_2, an insulating, two-dimensional cuprate. In the nonlinear optical experiments, we have performed pump-probe spectroscopy over a 1 eV spectral range, varying both the pump and the probe energy. We observe a pump-probe lineshape which varies considerably as a function of pump energy and temperature, and which differs sharply from those typically observed in band insulators. At low-temperatures, in particular, we observe an overall increase of spectral weight in our probe range, indicating that states are shifting over an energy scale larger than 1 eV. We attribute this behavior to the strongly correlated nature of the electronic structure in this material. Studies of the elementary excitations in other magnetic oxides, currently in progress, will be discussed.

Final Technical Report for DE-SC0008149

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buchanan, Kristen

The major goal of this project is to study spin waves in magnetic thin films, especially how spin waves respond to external stimuli. This is expected to lead to new insight into dynamic processes and new ideas for methods to control spin waves. Experimental studies are being done primarily using time- and spatially-resolved Brillouin light scattering (BLS) measurements on extended and patterned magnetic thin films. BLS is a versatile tool that provides a non-invasive probe of spin dynamics with frequencies of ~1 GHz to well over 100 GHz, diffraction-limited spatial resolution, 250-ps temporal resolution, and it is sensitive enough tomore » detect thermal magnons.« less

Localization in quantum field theory

NASA Astrophysics Data System (ADS)

Balachandran, A. P.

In non-relativistic quantum mechanics, Born’s principle of localization is as follows: For a single particle, if a wave function ψK vanishes outside a spatial region K, it is said to be localized in K. In particular, if a spatial region K‧ is disjoint from K, a wave function ψK‧ localized in K‧ is orthogonal to ψK. Such a principle of localization does not exist compatibly with relativity and causality in quantum field theory (QFT) (Newton and Wigner) or interacting point particles (Currie, Jordan and Sudarshan). It is replaced by symplectic localization of observables as shown by Brunetti, Guido and Longo, Schroer and others. This localization gives a simple derivation of the spin-statistics theorem and the Unruh effect, and shows how to construct quantum fields for anyons and for massless particles with “continuous” spin. This review outlines the basic principles underlying symplectic localization and shows or mentions its deep implications. In particular, it has the potential to affect relativistic quantum information theory and black hole physics.

Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling

PubMed Central

Levy, Miguel; Karki, Dolendra

2017-01-01

We present a formulation of electromagnetic spin-orbit coupling in magneto-optic media, and propose an alternative source of spin-orbit coupling to non-paraxial optics vortices. Our treatment puts forth a formulation of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media. It shows that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to unequal spin to orbital angular momentum conversion in magneto-optic media evanescent waves in opposite propagation-directions. Generation of free-space helicoidal beams based on this conversion is shown to be spin-helicity- and magnetization-dependent. We show that transverse-spin to orbital angular momentum coupling into magneto-optic waveguide media engenders spin-helicity-dependent unidirectional propagation. This unidirectional effect produces different orbital angular momenta in opposite directions upon excitation-spin-helicity reversals. PMID:28059120

Universal spin-momentum locked optical forces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalhor, Farid; Thundat, Thomas; Jacob, Zubin, E-mail: zjacob@purdue.edu

2016-02-08

Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported non-trivial optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, the direction of decay, and the direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and HE{sub 11} mode of an optical fiber. Furthermore, we explain how the recently reportedmore » phenomena of lateral optical force on chiral and achiral particles are caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Finally, we propose an experiment to identify the unique lateral forces arising from the transverse spin in the optical fiber and point to fundamental differences of the spin density from the well-known orbital angular momentum of light. Our work presents a unified view on spin-momentum locking and how it affects optical forces on chiral and achiral particles.« less

Communication: Evaluating non-empirical double hybrid functionals for spin-state energetics in transition-metal complexes

NASA Astrophysics Data System (ADS)

Wilbraham, Liam; Adamo, Carlo; Ciofini, Ilaria

2018-01-01

The computationally assisted, accelerated design of inorganic functional materials often relies on the ability of a given electronic structure method to return the correct electronic ground state of the material in question. Outlining difficulties with current density functionals and wave function-based approaches, we highlight why double hybrid density functionals represent promising candidates for this purpose. In turn, we show that PBE0-DH (and PBE-QIDH) offers a significant improvement over its hybrid parent functional PBE0 [as well as B3LYP* and coupled cluster singles and doubles with perturbative triples (CCSD(T))] when computing spin-state splitting energies, using high-level diffusion Monte Carlo calculations as a reference. We refer to the opposing influence of Hartree-Fock (HF) exchange and MP2, which permits higher levels of HF exchange and a concomitant reduction in electronic density error, as the reason for the improved performance of double-hybrid functionals relative to hybrid functionals. Additionally, using 16 transition metal (Fe and Co) complexes, we show that low-spin states are stabilised by increasing contributions from MP2 within the double hybrid formulation. Furthermore, this stabilisation effect is more prominent for high field strength ligands than low field strength ligands.

The expected spins of gravitational wave sources with isolated field binary progenitors

NASA Astrophysics Data System (ADS)

Zaldarriaga, Matias; Kushnir, Doron; Kollmeier, Juna A.

2018-01-01

We explore the consequences of dynamical evolution of field binaries composed of a primary black hole (BH) and a Wolf-Rayet (WR) star in the context of gravitational wave (GW) source progenitors. We argue, from general considerations, that the spin of the WR-descendent BH will be maximal in a significant number of cases due to dynamical effects. In other cases, the spin should reflect the natal spin of the primary BH which is currently theoretically unconstrained. We argue that the three currently published LIGO systems (GW150914, GW151226, LVT151012) suggest that this spin is small. The resultant effective spin distribution of gravitational wave sources should thus be bi-model if this classic GW progenitor channel is indeed dominant. While this is consistent with the LIGO detections thus far, it is in contrast to the three best-measured high-mass X-ray binary (HMXB) systems. A comparison of the spin distribution of HMXBs and GW sources should ultimately reveal whether or not these systems arise from similar astrophysical channels.

Electrically driven spin qubit based on valley mixing

NASA Astrophysics Data System (ADS)

Huang, Wister; Veldhorst, Menno; Zimmerman, Neil M.; Dzurak, Andrew S.; Culcer, Dimitrie

2017-02-01

The electrical control of single spin qubits based on semiconductor quantum dots is of great interest for scalable quantum computing since electric fields provide an alternative mechanism for qubit control compared with magnetic fields and can also be easier to produce. Here we outline the mechanism for a drastic enhancement in the electrically-driven spin rotation frequency for silicon quantum dot qubits in the presence of a step at a heterointerface. The enhancement is due to the strong coupling between the ground and excited states which occurs when the electron wave function overcomes the potential barrier induced by the interface step. We theoretically calculate single qubit gate times tπ of 170 ns for a quantum dot confined at a silicon/silicon-dioxide interface. The engineering of such steps could be used to achieve fast electrical rotation and entanglement of spin qubits despite the weak spin-orbit coupling in silicon.

The Spin Torque Lego - from spin torque nano-devices to advanced computing architectures

NASA Astrophysics Data System (ADS)

Grollier, Julie

2013-03-01

Spin transfer torque (STT), predicted in 1996, and first observed around 2000, brought spintronic devices to the realm of active elements. A whole class of new devices, based on the combined effects of STT for writing and Giant Magneto-Resistance or Tunnel Magneto-Resistance for reading has emerged. The second generation of MRAMs, based on spin torque writing : the STT-RAM, is under industrial development and should be out on the market in three years. But spin torque devices are not limited to binary memories. We will rapidly present how the spin torque effect also allows to implement non-linear nano-oscillators, spin-wave emitters, controlled stochastic devices and microwave nano-detectors. What is extremely interesting is that all these functionalities can be obtained using the same materials, the exact same stack, simply by changing the device geometry and its bias conditions. So these different devices can be seen as Lego bricks, each brick with its own functionality. During this talk, I will show how spin torque can be engineered to build new bricks, such as the Spintronic Memristor, an artificial magnetic nano-synapse. I will then give hints on how to assemble these bricks in order to build novel types of computing architectures, with a special focus on neuromorphic circuits. Financial support by the European Research Council Starting Grant NanoBrain (ERC 2010 Stg 259068) is acknowledged.

Chiral symmetry breaking and the spin content of hadrons

NASA Astrophysics Data System (ADS)

Glozman, L. Ya.; Lang, C. B.; Limmer, M.

2012-04-01

From the parton distributions in the infinite momentum frame, one finds that only about 30% of the nucleon spin is carried by spins of the valence quarks, which gave rise to the term “spin crisis”. Similar results hold for the lowest mesons, as it follows from the lattice simulations. We define the spin content of a meson in the rest frame and use a complete and orthogonal q¯q chiral basis and a unitary transformation from the chiral basis to the 2LJ basis. Then, given a mixture of different allowed chiral representations in the meson wave function at a given resolution scale, one can obtain its spin content at this scale. To obtain the mixture of the chiral representations in the meson, we measure in dynamical lattice simulations a ratio of couplings of interpolators with different chiral structure. For the ρ meson, we obtain practically the 3S1 state with no trace of the spin crisis. Then a natural question arises: which definition does reflect the spin content of a hadron?

Extraordinary SEAWs under influence of the spin-spin interaction and the quantum Bohm potential

NASA Astrophysics Data System (ADS)

Andreev, Pavel A.

2018-06-01

The separate spin evolution (SSE) of electrons causes the existence of the spin-electron acoustic wave. Extraordinary spin-electron acoustic waves (SEAWs) propagating perpendicular to the external magnetic field have a large contribution of the transverse electric field. Its spectrum has been studied in the quasi-classical limit at the consideration of the separate spin evolution. The spin-spin interaction and the quantum Bohm potential give contribution in the spectrum extraordinary SEAWs. This contribution is studied in this paper. Moreover, it is demonstrated that the spin-spin interaction leads to the existence of the extraordinary SEAWs if the SSE is neglected. It has been found that the SSE causes the instability of the extraordinary SEAW at the large wavelengths, but the quantum Bohm potential leads to the full stabilization of the spectrum.

Very narrow excited Ωc baryons

NASA Astrophysics Data System (ADS)

Karliner, Marek; Rosner, Jonathan L.

2017-06-01

Recently, LHCb reported the discovery of five extremely narrow excited Ωc baryons decaying into Ξc+K-. We interpret these baryons as bound states of a c quark and a P -wave s s diquark. For such a system, there are exactly five possible combinations of spin and orbital angular momentum. The narrowness of the states could be a signal that it is hard to pull apart the two s quarks in a diquark. We predict two of spin 1 /2 , two of spin 3 /2 , and one of spin 5 /2 , all with negative parity. Of the five states, two can decay in S -wave, and three can decay in D -wave. Some of the D -wave states might be narrower than the S -wave states. We discuss the relations among the five masses expected in the quark model and the likely spin assignments, and we compare them with the data. A similar pattern is expected for negative-parity excited Ωb states. An alternative interpretation is noted in which the heaviest two states are 2 S excitations with JP=1 /2+ and 3 /2+, while the lightest three are those with JP=3 /2- , 3 /2- , 5 /2- , expected to decay via D -waves. In this case, we expect JP=1 /2- Ωc states around 2904 and 2978 MeV.

Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au; Stamps, R. L.

2014-09-21

Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs inmore » the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.« less

Excitation and tailoring of diffractive spin-wave beams in NiFe using nonuniform microwave antennas

NASA Astrophysics Data System (ADS)

Körner, H. S.; Stigloher, J.; Back, C. H.

2017-09-01

We experimentally demonstrate by time-resolved scanning magneto-optical Kerr microscopy the possibility to locally excite multiple spin-wave beams in the dipolar-dominated regime in metallic NiFe films. For this purpose we employ differently shaped nonuniform microwave antennas consisting of several coplanar waveguide sections different in size, thereby adapting an approach for the generation of spin-wave beams in the exchange-dominated regime suggested by Gruszecki et al. [Sci. Rep. 6, 22367 (2016), 10.1038/srep22367]. The occurring spin-wave beams are diffractive and we show that the width of the beam and its widening as it propagates can be tailored by the shape and the length of the nonuniformity. Moreover, the propagation direction of the diffractive beams can be manipulated by changing the bias field direction.

Energy-level repulsion by spin-orbit coupling in two-dimensional Rydberg excitons

NASA Astrophysics Data System (ADS)

Stephanovich, V. A.; Sherman, E. Ya.; Zinner, N. T.; Marchukov, O. V.

2018-05-01

We study the effects of Rashba spin-orbit coupling on two-dimensional Rydberg exciton systems. Using analytical and numerical arguments we demonstrate that this coupling considerably modifies the wave functions and leads to a level repulsion that results in a deviation from the Poissonian statistics of the adjacent level distance distribution. This signifies the crossover to nonintegrability of the system and hints at the possibility of quantum chaos emerging. Such behavior strongly differs from the classical realization, where spin-orbit coupling produces highly entangled, chaotic electron trajectories in an exciton. We also calculate the oscillator strengths and show that randomization appears in the transitions between states with different total momenta.

Spin-Projected Matrix Product States: Versatile Tool for Strongly Correlated Systems.

PubMed

Li, Zhendong; Chan, Garnet Kin-Lic

2017-06-13

We present a new wave function ansatz that combines the strengths of spin projection with the language of matrix product states (MPS) and matrix product operators (MPO) as used in the density matrix renormalization group (DMRG). Specifically, spin-projected matrix product states (SP-MPS) are constructed as [Formula: see text], where [Formula: see text] is the spin projector for total spin S and |Ψ MPS (N,M) ⟩ is an MPS wave function with a given particle number N and spin projection M. This new ansatz possesses several attractive features: (1) It provides a much simpler route to achieve spin adaptation (i.e., to create eigenfunctions of Ŝ 2 ) compared to explicitly incorporating the non-Abelian SU(2) symmetry into the MPS. In particular, since the underlying state |Ψ MPS (N,M) ⟩ in the SP-MPS uses only Abelian symmetries, one does not need the singlet embedding scheme for nonsinglet states, as normally employed in spin-adapted DMRG, to achieve a single consistent variationally optimized state. (2) Due to the use of |Ψ MPS (N,M) ⟩ as its underlying state, the SP-MPS can be closely connected to broken-symmetry mean-field states. This allows one to straightforwardly generate the large number of broken-symmetry guesses needed to explore complex electronic landscapes in magnetic systems. Further, this connection can be exploited in the future development of quantum embedding theories for open-shell systems. (3) The sum of MPOs representation for the Hamiltonian and spin projector [Formula: see text] naturally leads to an embarrassingly parallel algorithm for computing expectation values and optimizing SP-MPS. (4) Optimizing SP-MPS belongs to the variation-after-projection (VAP) class of spin-projected theories. Unlike usual spin-projected theories based on determinants, the SP-MPS ansatz can be made essentially exact simply by increasing the bond dimensions in |Ψ MPS (N,M) ⟩. Computing excited states is also simple by imposing orthogonality constraints, which are simple to implement with MPS. To illustrate the versatility of SP-MPS, we formulate algorithms for the optimization of ground and excited states, develop perturbation theory based on SP-MPS, and describe how to evaluate spin-independent and spin-dependent properties such as the reduced density matrices. We demonstrate the numerical performance of SP-MPS with applications to several models typical of strong correlation, including the Hubbard model, and [2Fe-2S] and [4Fe-4S] model complexes.

Fermi wave vector for the partially spin-polarized composite-fermion Fermi sea

NASA Astrophysics Data System (ADS)

Balram, Ajit C.; Jain, J. K.

2017-12-01

The fully spin-polarized composite-fermion (CF) Fermi sea at the half-filled lowest Landau level has a Fermi wave vector kF*=√{4 π ρe } , where ρe is the density of electrons or composite fermions, supporting the notion that the interaction between composite fermions can be treated perturbatively. Away from ν =1 /2 , the area is seen to be consistent with kF*=√{4 π ρe } for ν <1 /2 but kF*=√{4 π ρh } for ν >1 /2 , where ρh is the density of holes in the lowest Landau level. This result is consistent with particle-hole symmetry in the lowest Landau level. We investigate in this article the Fermi wave vector of the spin-singlet CF Fermi sea (CFFS) at ν =1 /2 , for which particle-hole symmetry is not a consideration. Using the microscopic CF theory, we find that for the spin-singlet CFFS the Fermi wave vectors for up- and down-spin CFFSs at ν =1 /2 are consistent with kF*↑,↓=√{4 π ρe↑,↓ } , where ρe↑=ρe↓=ρe/2 , which implies that the residual interactions between composite fermions do not cause a nonperturbative correction for spin-singlet CFFS either. Our results suggest the natural conjecture that for arbitrary spin polarization the CF Fermi wave vectors are given by kF*↑=√{4 π ρe↑ } and kF*↓=√{4 π ρe↓ } .

Influence of the properties of soft collective spin wave modes on the magnetization reversal in finite arrays of dipolarly coupled magnetic dots

NASA Astrophysics Data System (ADS)

Stebliy, Maxim; Ognev, Alexey; Samardak, Alexander; Chebotkevich, Ludmila; Verba, Roman; Melkov, Gennadiy; Tiberkevich, Vasil; Slavin, Andrei

2015-06-01

Magnetization reversal in finite chains and square arrays of closely packed cylindrical magnetic dots, having vortex ground state in the absence of the external bias field, has been studied experimentally by measuring static hysteresis loops, and also analyzed theoretically. It has been shown that the field Bn of a vortex nucleation in a dot as a function of the finite number N of dots in the array's side may exhibit a monotonic or an oscillatory behavior depending on the array geometry and the direction of the external bias magnetic field. The oscillations in the dependence Bn(N) are shown to be caused by the quantization of the collective soft spin wave mode, which corresponds to the vortex nucleation in a finite array of dots. These oscillations are directly related to the form and symmetry of the dispersion law of the soft SW mode: the oscillation could appear only if the minimum of the soft mode spectrum is not located at any of the symmetric points inside the first Brillouin zone of the array's lattice. Thus, the purely static measurements of the hysteresis loops in finite arrays of coupled magnetic dots can yield important information about the properties of the collective spin wave excitations in these arrays.

Enhanced Spin Conductance of a Thin-Film Insulating Antiferromagnet

NASA Astrophysics Data System (ADS)

Bender, Scott A.; Skarsvâg, Hans; Brataas, Arne; Duine, Rembert A.

2017-08-01

We investigate spin transport by thermally excited spin waves in an antiferromagnetic insulator. Starting from a stochastic Landau-Lifshitz-Gilbert phenomenology, we obtain the out-of-equilibrium spin-wave properties. In linear response to spin biasing and a temperature gradient, we compute the spin transport through a normal-metal-antiferromagnet-normal-metal heterostructure. We show that the spin conductance diverges as one approaches the spin-flop transition; this enhancement of the conductance should be readily observable by sweeping the magnetic field across the spin-flop transition. The results from such experiments may, on the one hand, enhance our understanding of spin transport near a phase transition, and on the other be useful for applications that require a large degree of tunability of spin currents. In contrast, the spin Seebeck coefficient does not diverge at the spin-flop transition. Furthermore, the spin Seebeck coefficient is finite even at zero magnetic field, provided that the normal metal contacts break the symmetry between the antiferromagnetic sublattices.

Helical waves in easy-plane antiferromagnets

NASA Astrophysics Data System (ADS)

Semenov, Yuriy G.; Li, Xi-Lai; Xu, Xinyi; Kim, Ki Wook

2017-12-01

Effective spin torques can generate the Néel vector oscillations in antiferromagnets (AFMs). Here, it is theoretically shown that these torques applied at one end of a normal AFM strip can excite a helical type of spin wave in the strip whose properties are drastically different from characteristic spin waves. An analysis based on both a Néel vector dynamical equation and the micromagnetic simulation identifies the direction of magnetic anisotropy and the damping factor as the two key parameters determining the dynamics. Helical wave propagation requires the hard axis of the easy-plane AFM to be aligned with the traveling direction, while the damping limits its spatial extent. If the damping is neglected, the calculation leads to a uniform periodic domain wall structure. On the other hand, finite damping decelerates the helical wave rotation around the hard axis, ultimately causing stoppage of its propagation along the strip. With the group velocity staying close to spin-wave velocity at the wave front, the wavelength becomes correspondingly longer away from the excitation point. In a sufficiently short strip, a steady-state oscillation can be established whose frequency is controlled by the waveguide length as well as the excitation energy or torque.

Parallel database search and prime factorization with magnonic holographic memory devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khitun, Alexander

In this work, we describe the capabilities of Magnonic Holographic Memory (MHM) for parallel database search and prime factorization. MHM is a type of holographic device, which utilizes spin waves for data transfer and processing. Its operation is based on the correlation between the phases and the amplitudes of the input spin waves and the output inductive voltage. The input of MHM is provided by the phased array of spin wave generating elements allowing the producing of phase patterns of an arbitrary form. The latter makes it possible to code logic states into the phases of propagating waves and exploitmore » wave superposition for parallel data processing. We present the results of numerical modeling illustrating parallel database search and prime factorization. The results of numerical simulations on the database search are in agreement with the available experimental data. The use of classical wave interference may results in a significant speedup over the conventional digital logic circuits in special task data processing (e.g., √n in database search). Potentially, magnonic holographic devices can be implemented as complementary logic units to digital processors. Physical limitations and technological constrains of the spin wave approach are also discussed.« less

Parallel database search and prime factorization with magnonic holographic memory devices

NASA Astrophysics Data System (ADS)

Khitun, Alexander

2015-12-01

In this work, we describe the capabilities of Magnonic Holographic Memory (MHM) for parallel database search and prime factorization. MHM is a type of holographic device, which utilizes spin waves for data transfer and processing. Its operation is based on the correlation between the phases and the amplitudes of the input spin waves and the output inductive voltage. The input of MHM is provided by the phased array of spin wave generating elements allowing the producing of phase patterns of an arbitrary form. The latter makes it possible to code logic states into the phases of propagating waves and exploit wave superposition for parallel data processing. We present the results of numerical modeling illustrating parallel database search and prime factorization. The results of numerical simulations on the database search are in agreement with the available experimental data. The use of classical wave interference may results in a significant speedup over the conventional digital logic circuits in special task data processing (e.g., √n in database search). Potentially, magnonic holographic devices can be implemented as complementary logic units to digital processors. Physical limitations and technological constrains of the spin wave approach are also discussed.

Probing density and spin correlations in two-dimensional Hubbard model with ultracold fermions

NASA Astrophysics Data System (ADS)

Chan, Chun Fai; Drewes, Jan Henning; Gall, Marcell; Wurz, Nicola; Cocchi, Eugenio; Miller, Luke; Pertot, Daniel; Brennecke, Ferdinand; Koehl, Michael

2017-04-01

Quantum gases of interacting fermionic atoms in optical lattices is a promising candidate to study strongly correlated quantum phases of the Hubbard model such as the Mott-insulator, spin-ordered phases, or in particular d-wave superconductivity. We experimentally realise the two-dimensional Hubbard model by loading a quantum degenerate Fermi gas of 40 K atoms into a three-dimensional optical lattice geometry. High-resolution absorption imaging in combination with radiofrequency spectroscopy is applied to spatially resolve the atomic distribution in a single 2D layer. We investigate in local measurements of spatial correlations in both the density and spin sector as a function of filling, temperature and interaction strength. In the density sector, we compare the local density fluctuations and the global thermodynamic quantities, and in the spin sector, we observe the onset of non-local spin correlation, signalling the emergence of the anti-ferromagnetic phase. We would report our recent experimental endeavours to investigate further down in temperature in the spin sector.

On the damping of right hand circularly polarized waves in spin quantum plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iqbal, Z.; Hussain, A., E-mail: ah-gcu@yahoo.com; Department of Physics, Quaid-i-Azam University Islamabad, Islamabad 45320

2014-12-15

General dispersion relation for the right hand circularly polarized waves has been derived using non-relativistic spin quantum kinetic theory. Employing the derived dispersion relation, temporal and spatial damping of the right hand circularly polarized waves are studied for both the degenerate and non-degenerate plasma regimes for two different frequency domains: (i) k{sub ∥}v≫(ω+ω{sub ce}),(ω+ω{sub cg}) and (ii) k{sub ∥}v≪(ω+ω{sub ce}),(ω+ω{sub cg}). Comparison of the cold and hot plasma regimes shows that the right hand circularly polarized wave with spin-effects exists for larger k-values as compared to the spinless case, before it damps completely. It is also found that the spin-effectsmore » can significantly influence the phase and group velocities of the whistler waves in both the degenerate and non-degenerate regimes. The results obtained are also analyzed graphically for some laboratory parameters to demonstrate the physical significance of the present work.« less

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

NASA Astrophysics Data System (ADS)

Singamaneni, Srinivasa Rao; Stesmans, Andre; van Tol, Johan; Kosynkin, D. V.; Tour, James M.

2014-04-01

Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

Unidirectional spin-wave heat conveyer.

PubMed

An, T; Vasyuchka, V I; Uchida, K; Chumak, A V; Yamaguchi, K; Harii, K; Ohe, J; Jungfleisch, M B; Kajiwara, Y; Adachi, H; Hillebrands, B; Maekawa, S; Saitoh, E

2013-06-01

When energy is introduced into a region of matter, it heats up and the local temperature increases. This energy spontaneously diffuses away from the heated region. In general, heat should flow from warmer to cooler regions and it is not possible to externally change the direction of heat conduction. Here we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y3Fe5O12, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. When a Y3Fe5O12 film with low damping coefficients is used, spin waves are observed to emit heat at the sample end up to 10 mm away from the excitation source. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.

Nonperturbative parton distributions and the proton spin problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simonov, Yu. A., E-mail: simonov@itep.ru

2016-05-15

The Lorentz contracted form of the static wave functions is used to calculate the valence parton distributions for mesons and baryons, boosting the rest frame solutions of the path integral Hamiltonian. It is argued that nonperturbative parton densities are due to excitedmultigluon baryon states. A simplemodel is proposed for these states ensuring realistic behavior of valence and sea quarks and gluon parton densities at Q{sup 2} = 10 (GeV/c){sup 2}. Applying the same model to the proton spin problem one obtains Σ{sub 3} = 0.18 for the same Q{sup 2}.

Polarized fine structure in the photoluminescence excitation spectrum of a negatively charged quantum dot.

PubMed

Ware, M E; Stinaff, E A; Gammon, D; Doty, M F; Bracker, A S; Gershoni, D; Korenev, V L; Bădescu, S C; Lyanda-Geller, Y; Reinecke, T L

2005-10-21

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

Nonequilibrium Dynamics of Arbitrary-Range Ising Models with Decoherence: An Exact Analytic Solution

DTIC Science & Technology

2013-04-03

spontaneous deexcitation, spontaneous excitation, and elastic dephasing, respectively (see Fig. 1). We refer to the spin-changing processes (σ̂±) as Raman ...Series of Raman flips of the spin on site j can be formally accounted for as a magnetic field of strength 2Jjk/N acting for a time τ upj − τ downj . In...2σ̂±j , all Rayleigh jumps can be evaluated at t = 0 (their commutation with Raman jumps only affects the overall sign of the wave function). To the

DOE Office of Scientific and Technical Information (OSTI.GOV)

The four-dimensional scattering function S(Q,w) obtained by inelastic neutron scattering measurements provides unique "dynamical fingerprints" of the spin state and interactions present in complex magnetic materials. Extracting this information however is currently a slow and complex process that may take an expert -depending on the complexity of the system- up to several weeks of painstaking work to complete. Spin Wave Genie was created to abstract and automate this process. It strives to both reduce the time to complete this analysis and make these calculations more accessible to a broader group of scientists and engineers.

Damped spin waves in the intermediate ordered phases in Ni 3V 2O 8

DOE PAGES

Ehlers, Georg; Podlesnyak, Andrey A.; Frontzek, Matthias D.; ...

2015-06-09

Here, spin dynamics in the intermediate ordered phases (between 4 and 9 K) in Ni 3V 2O 8 have been studied with inelastic neutron scattering. It is found that the spin waves are very diffuse, indicative of short lived correlations and the coexistence of paramagnetic moments with the long-range ordered state.

Surface Andreev Bound States and Odd-Frequency Pairing in Topological Superconductor Junctions

NASA Astrophysics Data System (ADS)

Tanaka, Yukio; Tamura, Shun

2018-04-01

In this review, we summarize the achievement of the physics of surface Andreev bound states (SABS) up to now. The route of this activity has started from the physics of SABS of unconventional superconductors where the pair potential has a sign change on the Fermi surface. It has been established that SABS can be regarded as a topological edge state with topological invariant defined in the bulk Hamiltonian. On the other hand, SABS accompanies odd-frequency pairing like spin-triplet s-wave or spin-singlet p-wave. In a spin-triplet superconductor junction, induced odd-frequency pairing can penetrate into a diffusive normal metal (DN) attached to the superconductor. It causes so called anomalous proximity effect where the local density of states of quasiparticle in DN has a zero energy peak. When bulk pairing symmetry is spin-triplet px-wave, the anomalous proximity effect becomes prominent and the zero bias voltage conductance is always quantized independent of the resistance in DN and interface. Finally, we show that the present anomalous proximity effect is realized in an artificial topological superconducting system, where a nanowire with spin-orbit coupling and Zeeman field is put on the conventional spin-singlet s-wave superconductor.

Magnetosonic waves interactions in a spin-1/2 degenerate quantum plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Sheng-Chang, E-mail: lsc1128lsc@126.com; Han, Jiu-Ning

2014-03-15

We investigate the magnetosonic waves and their interactions in a spin-1/2 degenerate quantum plasma. With the help of the extended Poincaré-Lighthill-Kuo perturbation method, we derive two Korteweg-de Vries-Burgers equations to describe the magnetosonic waves. The parameter region where exists magnetosonic waves and the phase diagram of the compressive and rarefactive solitary waves with different plasma parameters are shown. We further explore the effects of quantum diffraction, quantum statistics, and electron spin magnetization on the head-on collisions of magnetosonic solitary waves. We obtain the collision-induced phase shifts (trajectory changes) analytically. Both for the compressive and rarefactive solitary waves, it is foundmore » that the collisions only lead to negative phase shifts. Our present study should be useful to understand the collective phenomena related to the magnetosonic wave collisions in degenerate plasmas like those in the outer shell of massive white dwarfs as well as to the potential applications of plasmas.« less

Superconductivity from fractionalized excitations in URu2Si2

NASA Astrophysics Data System (ADS)

Hsu, Chen-Hsuan; Chakravarty, Sudip

2014-10-01

An unconventional pairing mechanism in the heavy-fermion material URu2Si2 is studied. We propose a mixed singlet-triplet d-density wave to be the hidden-order state in URu2Si2. The exotic order is topologically nontrivial and supports a charge 2e skyrmionic spin texture, which is assumed to fractionalize into merons and antimerons at the deconfined quantum critical point. The interaction between these fractional particles results in a (pseudo)spin-singlet chiral d-wave superconducting state, which breaks time-reversal symmetry. Therefore, it is highly likely to produce a nonzero signal of the polar Kerr effect at the onset of the superconductivity, consistent with recent experiments. In addition, the nodal structures of the possible pairing functions in our model are consistent with the thermodynamic experiments in URu2Si2.

Spin wave Feynman diagram vertex computation package

NASA Astrophysics Data System (ADS)

Price, Alexander; Javernick, Philip; Datta, Trinanjan

Spin wave theory is a well-established theoretical technique that can correctly predict the physical behavior of ordered magnetic states. However, computing the effects of an interacting spin wave theory incorporating magnons involve a laborious by hand derivation of Feynman diagram vertices. The process is tedious and time consuming. Hence, to improve productivity and have another means to check the analytical calculations, we have devised a Feynman Diagram Vertex Computation package. In this talk, we will describe our research group's effort to implement a Mathematica based symbolic Feynman diagram vertex computation package that computes spin wave vertices. Utilizing the non-commutative algebra package NCAlgebra as an add-on to Mathematica, symbolic expressions for the Feynman diagram vertices of a Heisenberg quantum antiferromagnet are obtained. Our existing code reproduces the well-known expressions of a nearest neighbor square lattice Heisenberg model. We also discuss the case of a triangular lattice Heisenberg model where non collinear terms contribute to the vertex interactions.

Local spin-density-wave order inside vortex cores in multiband superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Vivek; Koshelev, Alexei E.

Coexistence of antiferromagnetic order with superconductivity in many families of newly discovered iron-based superconductors has renewed interest to this old problem. Due to competition between the two types of order, one can expect appearance of the antiferromagnetism inside the cores of the vortices generated by the external magnetic field. The structure of a vortex in type II superconductors holds significant importance from the theoretical and the application points of view. In this paper, we consider the internal vortex structure in a two-band s± superconductor near a spin-density-wave instability. We treat the problem in a completely self-consistent manner within the quasiclassicalmore » Eilenberger formalism. We study the structure of the s± superconducting order and magnetic field-induced spin-density-wave order near an isolated vortex. Finally, we examine the effect of this spin-density-wave state inside the vortex cores on the local density of states.« less

Local spin-density-wave order inside vortex cores in multiband superconductors

DOE PAGES

Mishra, Vivek; Koshelev, Alexei E.

2015-08-13

Coexistence of antiferromagnetic order with superconductivity in many families of newly discovered iron-based superconductors has renewed interest to this old problem. Due to competition between the two types of order, one can expect appearance of the antiferromagnetism inside the cores of the vortices generated by the external magnetic field. The structure of a vortex in type II superconductors holds significant importance from the theoretical and the application points of view. In this paper, we consider the internal vortex structure in a two-band s± superconductor near a spin-density-wave instability. We treat the problem in a completely self-consistent manner within the quasiclassicalmore » Eilenberger formalism. We study the structure of the s± superconducting order and magnetic field-induced spin-density-wave order near an isolated vortex. Finally, we examine the effect of this spin-density-wave state inside the vortex cores on the local density of states.« less

Temperature dependences of the electric polarization and wave number of incommensurate structures in multiferroics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pikin, S. A., E-mail: pikin@ns.crys.ras.ru

2016-05-15

It is shown that the electric polarization and wave number of incommensurate modulations, proportional to each other, increase according to the Landau law in spin multiferroic cycloids near the Néel temperature. In this case, the constant magnetization component (including the one for a conical spiral) is oriented perpendicular to the spin incommensurability wave vector. A similar temperature behavior should manifest itself for spin helicoids, the axes of which are oriented parallel to the polarization vector but their spin rotation planes are oriented perpendicular to the antiferromagnetic order plane. When the directions of axes of the magnetization helicoid and polarization vectormore » coincide, the latter is quadratic with respect to magnetization and linearly depends on temperature, whereas the incommensurate-modulation wave number barely depends on temperature. Structural distortions of unit cells for multiferroics of different types determine their axial behavior.« less

Dirty two-band superconductivity with interband pairing order

NASA Astrophysics Data System (ADS)

Asano, Yasuhiro; Sasaki, Akihiro; Golubov, Alexander A.

2018-04-01

We study theoretically the effects of random nonmagnetic impurities on the superconducting transition temperature T c in a two-band superconductor characterized by an equal-time s-wave interband pairing order parameter. Because of the two-band degree of freedom, it is possible to define a spin-triplet s-wave pairing order parameter as well as a spin-singlet s-wave order parameter. The former belongs to odd-band-parity symmetry class, whereas the latter belongs to even-band-parity symmetry class. In a spin-singlet superconductor, T c is insensitive to the impurity concentration when we estimate the self-energy due to the random impurity potential within the Born approximation. On the other hand in a spin-triplet superconductor, T c decreases with the increase of the impurity concentration. We conclude that Cooper pairs belonging to odd-band-parity symmetry class are fragile under the random impurity potential even though they have s-wave pairing symmetry.

Photodrive of magnetic bubbles via magnetoelastic waves

PubMed Central

Ogawa, Naoki; Koshibae, Wataru; Beekman, Aron Jonathan; Nagaosa, Naoto; Kubota, Masashi; Kawasaki, Masashi; Tokura, Yoshinori

2015-01-01

Precise control of magnetic domain walls continues to be a central topic in the field of spintronics to boost infotech, logic, and memory applications. One way is to drive the domain wall by current in metals. In insulators, the incoherent flow of phonons and magnons induced by the temperature gradient can carry the spins, i.e., spin Seebeck effect, but the spatial and time dependence is difficult to control. Here, we report that coherent phonons hybridized with spin waves, magnetoelastic waves, can drive magnetic bubble domains, or curved domain walls, in an iron garnet, which are excited by ultrafast laser pulses at a nonabsorbing photon energy. These magnetoelastic waves were imaged by time-resolved Faraday microscopy, and the resultant spin transfer force was evaluated to be larger for domain walls with steeper curvature. This will pave a path for the rapid spatiotemporal control of magnetic textures in insulating magnets. PMID:26150487

Photodrive of magnetic bubbles via magnetoelastic waves.

PubMed

Ogawa, Naoki; Koshibae, Wataru; Beekman, Aron Jonathan; Nagaosa, Naoto; Kubota, Masashi; Kawasaki, Masashi; Tokura, Yoshinori

2015-07-21

Precise control of magnetic domain walls continues to be a central topic in the field of spintronics to boost infotech, logic, and memory applications. One way is to drive the domain wall by current in metals. In insulators, the incoherent flow of phonons and magnons induced by the temperature gradient can carry the spins, i.e., spin Seebeck effect, but the spatial and time dependence is difficult to control. Here, we report that coherent phonons hybridized with spin waves, magnetoelastic waves, can drive magnetic bubble domains, or curved domain walls, in an iron garnet, which are excited by ultrafast laser pulses at a nonabsorbing photon energy. These magnetoelastic waves were imaged by time-resolved Faraday microscopy, and the resultant spin transfer force was evaluated to be larger for domain walls with steeper curvature. This will pave a path for the rapid spatiotemporal control of magnetic textures in insulating magnets.

Femtosecond laser excitation of multiple spin waves and composition dependence of Gilbert damping in full-Heusler Co{sub 2}Fe{sub 1−x}Mn{sub x}Al films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Chuyuan; Li, Shufa; Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn, E-mail: jhzhao@red.semi.ac.cn

2013-12-02

Spin-wave dynamics in 30 nm thick Co{sub 2}Fe{sub 1−x}Mn{sub x}Al full-Heusler films is investigated using time-resolved magneto-optical polar Kerr spectroscopy under an external field perpendicular to films. Damon-Eshbach (DE) and the first-order perpendicular standing spin-wave (PSSW) modes are observed simultaneously in four samples with x = 0, 0.3, 0.7, and 1. The frequency of DE and PSSW modes does not apparently depend on composition x, but damping of DE mode significantly on x and reaches the minimum as x = 0.7. The efficient coherent excitation of DE spin wave exhibits the promising application of Co{sub 2}Fe{sub 0.3}Mn{sub 0.7}Al films in magnonic devices.

Full control of the spin-wave damping in a magnetic insulator using spin orbit torque

NASA Astrophysics Data System (ADS)

Klein, Olivier

2015-03-01

The spin-orbit interaction (SOI) has been an interesting and useful addition in the field of spintronics by opening it to non-metallic magnet. It capitalizes on adjoining a strong SOI normal metal next to a thin magnetic layer. The SOI converts a charge current, Jc, into a spin current, Js, with an efficiency parametrized by ΘSH, the spin Hall angle. An important benefit of the SOI is that Jc and Js are linked through a cross-product, allowing a charge current flowing in-plane to produce a spin current flowing out-of-plane. Hence it enables the transfer of spin angular momentum to non-metallic materials and in particular to insulating oxides, which offer improved performance compared to their metallic counterparts. Among all oxides, Yttrium Iron Garnet (YIG) holds a special place for having the lowest known spin-wave (SW) damping factor. Until recently the transmission of spin current through the YIG|Pt interface has been subject to debate. While numerous experiments have reported that Js produced by the excitation of ferromagnetic resonance (FMR) in YIG can cross efficiently the YIG|Pt interface and be converted into Jc in Pt through the inverse spin Hall effect (ISHE), most attempts to observe the reciprocal effect, where Js produced in Pt by the direct spin Hall effect (SHE) is transferred to YIG, resulting in damping compensation, have failed. This has been raising fundamental questions about the reciprocity of the spin transparency of the interface between a metal and a magnetic insulator. In this talk it will be demonstrated that the threshold current for damping compensation can be reached in a 5 μm diameter YIG(20nm)|Pt(7nm) disk. Reduction of both the thickness and lateral size of a YIG-structure were key to reach the microwave generation threshold current, Jc*. The experimental evidence rests upon the measurement of the ferromagnetic resonance linewidth as a function of Idc using a magnetic resonance force microscope (MRFM). It is shwon that the magnetic losses of spin-wave modes existing in the magnetic insulator can be reduced or enhanced by at least a factor of five depending on the polarity and intensity of the in-plane dc current, Idc. Complete compensation of the damping of the fundamental mode by spin-orbit torque is reached for a current density of ~ 3 .1011 A.m-2, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime. This result opens up a new area of research on the electronic control of the damping of YIG-nanostructures.

Structural, electronic and magnetic properties of metal thiophosphate InPS4

NASA Astrophysics Data System (ADS)

Rajpoot, Priyanka; Nayak, Vikas; Kumari, Meena; Yadav, Priya; Nautiyal, Shashank; Verma, U. P.

2017-05-01

The non-centrosymmetric crystal, InPS4, has been investigated by means of density functional theory (DFT). In this paper we have calculated the structural parameters, electronic band structures, density of states plot and magnetic properties using full potential linearized augmented plane wave (FP-LAPW) method. The exchange correlation has been solved employing the generalised gradient approximation due to Perdew-Burke-Ernzerhof. The calculations are performed both without spin as well as spin polarized. The results show that InPS4 is an indirect band gap semiconductor with (N-Г) energy gap of 2.32eV (without spin) and 1.86eV in spin up and down channels.The obtained lattice parameters and energy gap agree well with the experimental results. Our reported magnetic moment results show that the property of InPS4is nonmagnetic.

Breakdown of the Wigner-Mattis theorem in semiconductor carbon-nanotube quantum dots

NASA Astrophysics Data System (ADS)

Rontani, Massimo; Secchi, Andrea; Manghi, Franca

2009-03-01

The Wigner-Mattis theorem states the ground state of two bound electrons, in the absence of the magnetic field, is always a spin-singlet. We predict the opposite result --a triplet- for two electrons in a quantum dot defined in a semiconductor carbon nanotube. The claim is supported by extensive many-body calculations based on the accurate configuration interaction code DONRODRIGO (www.s3.infm.t/donrodrigo). The crux of the matter is the peculiar two-valley structure of low-energy states, which encodes a pseudo-spin degree of freedom. The spin polarization of the ground state corresponds to a pseudo-spin singlet, which is selected by the inter-valley short-range Coulomb interaction. Single-electron excitation spectra and STM wave function images may validate this scenario, as shown by our numerical simulations.

Scalar formalism for non-Abelian gauge theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hostler, L.C.

1986-09-01

The gauge field theory of an N-italic-dimensional multiplet of spin- 1/2 particles is investigated using the Klein--Gordon-type wave equation )Pi x (1+i-italicsigma) x Pi+m-italic/sup 2/)Phi = 0, Pi/sub ..mu../equivalentpartial/partiali-italicx-italic/sub ..mu../-e-italicA-italic/sub ..mu../, investigated before by a number of authors, to describe the fermions. Here Phi is a 2 x 1 Pauli spinor, and sigma repesents a Lorentz spin tensor whose components sigma/sub ..mu..//sub ..nu../ are ordinary 2 x 2 Pauli spin matrices. Feynman rules for the scalar formalism for non-Abelian gauge theory are derived starting from the conventional field theory of the multiplet and converting it to the new description. Themore » equivalence of the new and the old formalism for arbitrary radiative processes is thereby established. The conversion to the scalar formalism is accomplished in a novel way by working in terms of the path integral representation of the generating functional of the vacuum tau-functions, tau(2,1, xxx 3 xxx)equivalent<0-chemically bondT-italic(Psi/sub in/(2) Psi-bar/sub in/(1) xxx A-italic/sub ..mu../(3)/sub in/ xxx S-italic)chemically bond0->, where Psi/sub in/ is a Heisenberg operator belonging to a 4N-italic x 1 Dirac wave function of the multiplet. The Feynman rules obtained generalize earlier results for the Abelian case of quantum electrodynamics.« less

Spin-lattice relaxation and the calculation of gain, pump power, and noise temperature in ruby

NASA Technical Reports Server (NTRS)

Lyons, J. R.

1989-01-01

The use of a quantitative analysis of the dominant source of relaxation in ruby spin systems to make predictions of key maser amplifier parameters is described. The spin-lattice Hamiltonian which describes the interaction of the electron spins with the thermal vibrations of the surrounding lattice is obtained from the literature. Taking into account the vibrational anisotropy of ruby, Fermi's rule is used to calculate the spin transition rates between the maser energy levels. The spin population rate equations are solved for the spin transition relaxation times, and a comparison with previous calculations is made. Predictions of ruby gain, inversion ratio, and noise temperature as a function of physical temperature are made for 8.4-GHz and 32-GHz maser pumping schemes. The theory predicts that ruby oriented at 90 deg will have approximately 50 percent higher gain in dB and slightly lower noise temperature than a 54.7-deg ruby at 32 GHz (assuming pump saturation). A specific calculation relating pump power to inversion ratio is given for a single channel of the 32-GHz reflected wave maser.

Magnetic spiral induced by strong correlations in MnAu2

NASA Astrophysics Data System (ADS)

Glasbrenner, J. K.; Bussmann, K. M.; Mazin, I. I.

2014-10-01

The compound MnAu2 is one of the oldest known spin-spiral materials, yet the nature of the spiral state is still not clear. The spiral cannot be explained via relativistic effects due to the short pitch of the spiral and the weakness of the spin-orbit interaction in Mn, and another common mechanism, nesting, is ruled out as direct calculations show no features at the relevant wave vector. We propose that the spiral state is induced by a competition between the short-range antiferromagnetic exchange and a long-range interaction induced by the polarization of Au bands, similar to double exchange. We find that, contrary to earlier reports, the ground state in standard density functional theory is ferromagnetic, i.e., the latter interaction dominates. However, an accounting for Coulomb correlations via a Hubbard U suppresses the Schrieffer-Wolff-type s-d magnetic interaction between Mn and Au faster than the superexchange interaction, favoring a spin-spiral state. For realistic values of U, the resulting spiral wave vector is in close agreement with experiment.

Spin-wave resonances and surface spin pinning in Ga1-xMnxAs thin films

NASA Astrophysics Data System (ADS)

Bihler, C.; Schoch, W.; Limmer, W.; Goennenwein, S. T. B.; Brandt, M. S.

2009-01-01

We investigate the dependence of the spin-wave resonance (SWR) spectra of Ga0.95Mn0.05As thin films on the sample treatment. We find that for the external magnetic field perpendicular to the film plane, the SWR spectrum of the as-grown thin films and the changes upon etching and short-term hydrogenation can be quantitatively explained via a linear gradient in the uniaxial magnetic anisotropy field in growth direction. The model also qualitatively explains the SWR spectra observed for the in-plane easy-axis orientation of the external magnetic field. Furthermore, we observe a change in the effective surface spin pinning of the partially hydrogenated sample, which results from the tail in the hydrogen-diffusion profile. The latter leads to a rapidly changing hole concentration/magnetic anisotropy profile acting as a barrier for the spin-wave excitations. Therefore, short-term hydrogenation constitutes a simple method to efficiently manipulate the surface spin pinning.

Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polzikova, N. I., E-mail: polz@cplire.ru; Alekseev, S. G.; Pyataikin, I. I.

2016-05-15

We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determinedmore » by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.« less

Forward volume and surface magnetostatic modes in an yttrium iron garnet film for out-of-plane magnetic fields: Theory and experiment

NASA Astrophysics Data System (ADS)

Lim, Jinho; Bang, Wonbae; Trossman, Jonathan; Amanov, Dovran; Ketterson, John B.

2018-05-01

We present experimental and theoretical results on the propagation of magnetostatic spin waves in a film of yttrium iron garnet (YIG) for out-of-plane magnetic fields for which propagation in opposite directions is nonreciprocal in the presence of a metal layer. The plane studied is defined by the film normal n and n × k where k is the wave vector of the mode. Spin waves in this setting are classified as forward volume waves or surface waves and display non-reciprocity in the presence of an adjacent metal layer except for when H//n. The measurements are carried out in a transmission geometry, and a microwave mixer is used to measure the change of phase, and with it the evolution of wavevector, of the arriving spin wave with external magnetic field.

Non-autonomous multi-rogue waves for spin-1 coupled nonlinear Gross-Pitaevskii equation and management by external potentials.

PubMed

Li, Li; Yu, Fajun

2017-09-06

We investigate non-autonomous multi-rogue wave solutions in a three-component(spin-1) coupled nonlinear Gross-Pitaevskii(GP) equation with varying dispersions, higher nonlinearities, gain/loss and external potentials. The similarity transformation allows us to relate certain class of multi-rogue wave solutions of the spin-1 coupled nonlinear GP equation to the solutions of integrable coupled nonlinear Schrödinger(CNLS) equation. We study the effect of time-dependent quadratic potential on the profile and dynamic of non-autonomous rogue waves. With certain requirement on the backgrounds, some non-autonomous multi-rogue wave solutions exhibit the different shapes with two peaks and dip in bright-dark rogue waves. Then, the managements with external potential and dynamic behaviors of these solutions are investigated analytically. The results could be of interest in such diverse fields as Bose-Einstein condensates, nonlinear fibers and super-fluids.

Observation of Self-Cavitating Envelope Dispersive Shock Waves in Yttrium Iron Garnet Thin Films

NASA Astrophysics Data System (ADS)

Janantha, P. A. Praveen; Sprenger, Patrick; Hoefer, Mark A.; Wu, Mingzhong

2017-07-01

The formation and properties of envelope dispersive shock wave (DSW) excitations from repulsive nonlinear waves in a magnetic film are studied. Experiments involve the excitation of a spin wave step pulse in a low-loss magnetic Y3Fe5O12 thin film strip, in which the spin wave amplitude increases rapidly, realizing the canonical Riemann problem of shock theory. Under certain conditions, the envelope of the spin wave pulse evolves into a DSW that consists of an expanding train of nonlinear oscillations with amplitudes increasing from front to back, terminated by a black soliton. The onset of DSW self-cavitation, indicated by a point of zero power and a concomitant 180° phase jump, is observed for sufficiently large steps, indicative of the bidirectional dispersive hydrodynamic nature of the DSW. The experimental observations are interpreted with theory and simulations of the nonlinear Schrödinger equation.

Boundary perimeter Bethe ansatz

NASA Astrophysics Data System (ADS)

Frassek, Rouven

2017-06-01

We study the partition function of the six-vertex model in the rational limit on arbitrary Baxter lattices with reflecting boundary. Every such lattice is interpreted as an invariant of the twisted Yangian. This identification allows us to relate the partition function of the vertex model to the Bethe wave function of an open spin chain. We obtain the partition function in terms of creation operators on a reference state from the algebraic Bethe ansatz and as a sum of permutations and reflections from the coordinate Bethe ansatz.

Generalized spin-wave theory: Application to the bilinear-biquadratic model

NASA Astrophysics Data System (ADS)

Muniz, Rodrigo A.; Kato, Yasuyuki; Batista, Cristian D.

2014-08-01

We present a mathematical framework for the multi-boson approach that has been used several times for treating spin systems. We demonstrate that the multi-boson approach corresponds to a generalization of the traditional spin-wave theory from SU(2) to SU(N), where N is the number of states of the local degree of freedom. Low-energy excitations are waves of the local order parameter that fluctuates in the SU(N) space of unitary transformations of the local spin states, instead of the SU(2) space of local spin rotations. Since the generators of the SU(N) group can be represented as bilinear forms in N-flavored bosons, the low-energy modes of the generalized spin-wave theory (GSWT) are described with N-1 different bosons, which provide a more accurate description of low-energy excitations even for the usual ferromagnetic and antiferromagnetic phases. The generalization enables the treatment of quantum spin systems whose ground states exhibit multipolar ordering as well as the detection of instabilities of magnetically ordered states (dipolar ordering) towards higher multipolar orderings. We illustrate the advantages of the GSWT by applying it to a bilinear-biquadratic model of arbitrary spin S on hypercubic lattices, and then analyzing the spectrum of dipolar phases in order to find their instabilities. In contrast to the known results for S=1 when the biquadratic term in the Hamiltonian is negative, we find that there is no nematic phase between the ferromagnetic or antiferromagnetic orderings for S>1.

Competition of density waves and quantum multicritical behavior in Dirac materials from functional renormalization

NASA Astrophysics Data System (ADS)

Classen, Laura; Herbut, Igor F.; Janssen, Lukas; Scherer, Michael M.

2016-03-01

We study the competition of spin- and charge-density waves and their quantum multicritical behavior for the semimetal-insulator transitions of low-dimensional Dirac fermions. Employing the effective Gross-Neveu-Yukawa theory with two order parameters as a model for graphene and a growing number of other two-dimensional Dirac materials allows us to describe the physics near the multicritical point at which the semimetallic and the spin- and charge-density-wave phases meet. With the help of a functional renormalization group approach, we are able to reveal a complex structure of fixed points, the stability properties of which decisively depend on the number of Dirac fermions Nf. We give estimates for the critical exponents and observe crucial quantitative corrections as compared to the previous first-order ɛ expansion. For small Nf, the universal behavior near the multicritical point is determined by the chiral Heisenberg universality class supplemented by a decoupled, purely bosonic, Ising sector. At large Nf, a novel fixed point with nontrivial couplings between all sectors becomes stable. At intermediate Nf, including the graphene case (Nf=2 ), no stable and physically admissible fixed point exists. Graphene's phase diagram in the vicinity of the intersection between the semimetal, antiferromagnetic, and staggered density phases should consequently be governed by a triple point exhibiting first-order transitions.

Gravitational-wave bursts and stochastic background from superfluid vortex avalanches during pulsar glitches

NASA Astrophysics Data System (ADS)

Warszawski, L.; Melatos, A.

2012-07-01

The current-quadrupole gravitational-wave signal emitted during the spin-up phase of a pulsar glitch is calculated from first principles by modelling the vortex dynamics observed in recent Gross-Pitaevskii simulations of pinned, decelerating quantum condensates. Homogeneous and inhomogeneous unpinning geometries, representing creep- and avalanche-like glitches, provide lower and upper bounds on the gravitational-wave signal strength, respectively. The signal arising from homogeneous glitches is found to scale with the square root of glitch size, whereas the signal from inhomogeneous glitches scales proportional to glitch size. The signal is also computed as a function of vortex travel distance and stellar angular velocity. Convenient amplitude scalings are derived as functions of these parameters. For the typical astrophysical situation, where the glitch duration (in units of the spin period) is large compared to the vortex travel distance (in units of the stellar radius), an individual glitch from an object 1 kpc from Earth generates a wave strain of 10-24[(Δω/ω)/10-7](ω/102 rad s-1)3(Δr/10-2 m)-1, where Δr is the average distance travelled by a vortex during a glitch, Δω/ω is the fractional glitch size and ω is the pulsar angular velocity. The non-detection of a signal from the 2006 Vela glitch in data from the fifth science run conducted by the Laser Interferometer Gravitational-Wave Observatory implies that the glitch duration exceeds ˜10-4 ms. This represents the first observational lower bound on glitch duration to be obtained.

Invariance of Topological Indices Under Hilbert Space Truncation

DOE PAGES

Huang, Zhoushen; Zhu, Wei; Arovas, Daniel P.; ...

2018-01-05

Here, we show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z 2 topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement. As a possiblemore » application, we propose a partial quantum tomography scheme from which the topological index of a generic multicomponent wave function can be extracted by measuring only a small subset of wave function components, equivalent to the measurement of a bulk entanglement topological index.« less

Constructing topological models by symmetrization: A projected entangled pair states study

NASA Astrophysics Data System (ADS)

Fernández-González, Carlos; Mong, Roger S. K.; Landon-Cardinal, Olivier; Pérez-García, David; Schuch, Norbert

2016-10-01

Symmetrization of topologically ordered wave functions is a powerful method for constructing new topological models. Here we study wave functions obtained by symmetrizing quantum double models of a group G in the projected entangled pair states (PEPS) formalism. We show that symmetrization naturally gives rise to a larger symmetry group G ˜ which is always non-Abelian. We prove that by symmetrizing on sufficiently large blocks, one can always construct wave functions in the same phase as the double model of G ˜. In order to understand the effect of symmetrization on smaller patches, we carry out numerical studies for the toric code model, where we find strong evidence that symmetrizing on individual spins gives rise to a critical model which is at the phase transitions of two inequivalent toric codes, obtained by anyon condensation from the double model of G ˜.

Anatomy of quantum critical wave functions in dissipative impurity problems

NASA Astrophysics Data System (ADS)

Blunden-Codd, Zach; Bera, Soumya; Bruognolo, Benedikt; Linden, Nils-Oliver; Chin, Alex W.; von Delft, Jan; Nazir, Ahsan; Florens, Serge

2017-02-01

Quantum phase transitions reflect singular changes taking place in a many-body ground state; however, computing and analyzing large-scale critical wave functions constitutes a formidable challenge. Physical insights into the sub-Ohmic spin-boson model are provided by the coherent-state expansion (CSE), which represents the wave function by a linear combination of classically displaced configurations. We find that the distribution of low-energy displacements displays an emergent symmetry in the absence of spontaneous symmetry breaking while experiencing strong fluctuations of the order parameter near the quantum critical point. Quantum criticality provides two strong fingerprints in critical low-energy modes: an algebraic decay of the average displacement and a constant universal average squeezing amplitude. These observations, confirmed by extensive variational matrix-product-state (VMPS) simulations and field theory arguments, offer precious clues into the microscopics of critical many-body states in quantum impurity models.

Invariance of Topological Indices Under Hilbert Space Truncation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhoushen; Zhu, Wei; Arovas, Daniel P.

Here, we show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z 2 topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement. As a possiblemore » application, we propose a partial quantum tomography scheme from which the topological index of a generic multicomponent wave function can be extracted by measuring only a small subset of wave function components, equivalent to the measurement of a bulk entanglement topological index.« less

High-temperature charge density wave correlations in La1.875Ba0.125CuO4 without spin–charge locking

PubMed Central

Lorenzana, J.; Seibold, G.; Peng, Y. Y.; Amorese, A.; Yakhou-Harris, F.; Kummer, K.; Brookes, N. B.; Konik, R. M.; Thampy, V.; Gu, G. D.; Ghiringhelli, G.; Braicovich, L.

2017-01-01

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La1.875Ba0.125CuO4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. This indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates. PMID:29114049

Chain and ladder models with two-body interactions and analytical ground states

NASA Astrophysics Data System (ADS)

Manna, Sourav; Nielsen, Anne E. B.

2018-05-01

We consider a family of spin-1 /2 models with few-body, SU(2)-invariant Hamiltonians and analytical ground states related to the one-dimensional (1D) Haldane-Shastry wave function. The spins are placed on the surface of a cylinder, and the standard 1D Haldane-Shastry model is obtained by placing the spins with equal spacing in a circle around the cylinder. Here, we show that another interesting family of models with two-body exchange interactions is obtained if we instead place the spins along one or two lines parallel to the cylinder axis, giving rise to chain and ladder models, respectively. We can change the scale along the cylinder axis without changing the radius of the cylinder. This gives us a parameter that controls the ratio between the circumference of the cylinder and all other length scales in the system. We use Monte Carlo simulations and analytical investigations to study how this ratio affects the properties of the models. If the ratio is large, we find that the two legs of the ladder decouple into two chains that are in a critical phase with Haldane-Shastry-like properties. If the ratio is small, the wave function reduces to a product of singlets. In between, we find that the behavior of the correlations and the Renyi entropy depends on the distance considered. For small distances the behavior is critical, and for long distances the correlations decay exponentially and the entropy shows an area law behavior. The distance up to which there is critical behavior gets larger as the ratio increases.

Momentum-resolved radio-frequency spectroscopy of a spin-orbit-coupled atomic Fermi gas near a Feshbach resonance in harmonic traps

NASA Astrophysics Data System (ADS)

Peng, Shi-Guo; Liu, Xia-Ji; Hu, Hui; Jiang, Kaijun

2012-12-01

We theoretically investigate the momentum-resolved radio-frequency spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling. The system is qualitatively modeled as an ideal gas mixture of atoms and molecules, in which the properties of molecules, such as the wave function, binding energy, and effective mass, are determined from the two-particle solution of two interacting atoms. We calculate separately the radio-frequency response from atoms and molecules at finite temperatures by using the standard Fermi golden rule and take into account the effect of harmonic traps within local density approximation. The total radio-frequency spectroscopy is discussed as functions of temperature and spin-orbit coupling strength. Our results give a qualitative picture of radio-frequency spectroscopy of a resonantly interacting spin-orbit-coupled Fermi gas and can be directly tested in atomic Fermi gases of 40K atoms at Shanxi University and 6Li atoms at the Massachusetts Institute of Technology.

Classification of "multipole" superconductivity in multiorbital systems and its implications

NASA Astrophysics Data System (ADS)

Nomoto, T.; Hattori, K.; Ikeda, H.

2016-11-01

Motivated by a growing interest in multiorbital superconductors with spin-orbit interactions, we perform the group-theoretical classification of various unconventional superconductivity emerging in symmorphic O , D4, and D6 space groups. The generalized Cooper pairs, which we here call "multipole" superconductivity, possess spin-orbital coupled (multipole) degrees of freedom, instead of the conventional spin singlet/triplet in single-orbital systems. From the classification, we obtain the following key consequences, which have never been focused in the long history of research in this field: (1) A superconducting gap function with Γ9⊗Γ9 in D6 possesses nontrivial momentum dependence different from the usual spin-1/2 classification. (2) Unconventional gap structure can be realized in the BCS approximation of purely local (onsite) interactions irrespective of attraction/repulsion. It implies the emergence of an electron-phonon (e-ph) driven unconventional superconductivity. (3) Reflecting symmetry of orbital basis functions there appear not symmetry protected but inevitable line nodes/gap minima, and thus, anisotropic s -wave superconductivity can be naturally explained even in the absence of competing fluctuations.

Bias-free spin-wave phase shifter for magnonic logic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louis, Steven; Tyberkevych, Vasyl; Slavin, Andrei

2016-06-15

A design of a magnonic phase shifter operating without an external bias magnetic field is proposed. The phase shifter uses a localized collective spin wave mode propagating along a domain wall “waveguide” in a dipolarly-coupled magnetic dot array with a chessboard antiferromagnetic (CAFM) ground state. It is demonstrated numerically that the remagnetization of a single magnetic dot adjacent to the domain wall waveguide introduces a controllable phase shift in the propagating spin wave mode without significant change to the mode amplitude. It is also demonstrated that a logic XOR gate can be realized in the same system.

Spin waves in micro-structured yttrium iron garnet nanometer-thick films

DOE PAGES

Jungfleisch, Matthias B.; Zhang, Wei; Jiang, Wanjun; ...

2015-03-24

Here, we investigated the spin-wave propagation in a micro-structured yttrium iron garnet waveguide of 40 nm thickness. Utilizing spatially-resolved Brillouin light scattering microscopy, an exponential decay of the spinwave amplitude of 10 μm was observed. This leads to an estimated Gilbert damping constant of α = (8.79 ± 0.73) x 10 $-$4, which is larger than damping values obtained through ferromagnetic resonance measurements in unstructured films. Furthermore, we compared the theoretically calculated spatial interference of waveguide modes to the spin-wave pattern observed experimentally by means of Brillouin light scattering spectroscopy.

Intrinsic superspin Hall current

NASA Astrophysics Data System (ADS)

Linder, Jacob; Amundsen, Morten; Risinggârd, Vetle

2017-09-01

We discover an intrinsic superspin Hall current: an injected charge supercurrent in a Josephson junction containing heavy normal metals and a ferromagnet generates a transverse spin supercurrent. There is no accompanying dissipation of energy, in contrast to the conventional spin Hall effect. The physical origin of the effect is an antisymmetric spin density induced among transverse modes ky near the interface of the superconductor arising due to the coexistence of p -wave and conventional s -wave superconducting correlations with a belonging phase mismatch. Our predictions can be tested in hybrid structures including thin heavy metal layers combined with strong ferromagnets and ordinary s -wave superconductors.

Electromagnetic wave propagating along a space curve

NASA Astrophysics Data System (ADS)

Lai, Meng-Yun; Wang, Yong-Long; Liang, Guo-Hua; Wang, Fan; Zong, Hong-Shi

2018-03-01

By using the thin-layer approach, we derive the effective equation for the electromagnetic wave propagating along a space curve. We find intrinsic spin-orbit, extrinsic spin-orbit, and extrinsic orbital angular-momentum and intrinsic orbital angular-momentum couplings induced by torsion, which can lead to geometric phase, spin, and orbital Hall effects. And we show the helicity inversion induced by curvature that can convert a right-handed circularly polarized electromagnetic wave into a left-handed polarized one, vice versa. Finally, we demonstrate that the gauge invariance of the effective dynamics is protected by the geometrically induced gauge potential.

Effects of the magnetic field variation on the spin wave interference in a magnetic cross junction

NASA Astrophysics Data System (ADS)

Balynskiy, M.; Chiang, H.; Kozhevnikov, A.; Dudko, G.; Filimonov, Y.; Balandin, A. A.; Khitun, A.

2018-05-01

This article reports results of the investigation of the effect of the external magnetic field variation on the spin wave interference in a magnetic cross junction. The experiments were performed using a micrometer scale Y3Fe5O12 cross structure with a set of micro-antennas fabricated on the edges of the cross arms. Two of the antennas were used for the spin wave excitation while a third antenna was used for detecting the inductive voltage produced by the interfering spin waves. It was found that a small variation of the bias magnetic field may result in a significant change of the output inductive voltage. The effect is most prominent under the destructive interference condition. The maximum response exceeds 30 dB per 0.1 Oe at room temperature. It takes a relatively small bias magnetic field variation of about 1 Oe to drive the system from the destructive to the constructive interference conditions. The switching is accompanied by a significant, up to 50 dB, change in the output voltage. The obtained results demonstrate a feasibility of the efficient spin wave interference control by an external magnetic field, which may be utilized for engineering novel type of magnetometers and magnonic logic devices.

Neutron-scattering evidence for a periodically modulated superconducting phase in the underdoped cuprate La 1.905Ba 0.095CuO 4

DOE PAGES

Xu, Zhijun; Stock, C.; Chi, Songxue; ...

2014-10-01

The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La 1.905Ba 0.095CuO 4. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La 2-xSr xCuO 4 and YBa 2Cu 3O 6+x.

Integrability in heavy quark effective theory

NASA Astrophysics Data System (ADS)

Braun, Vladimir M.; Ji, Yao; Manashov, Alexander N.

2018-06-01

It was found that renormalization group equations in the heavy-quark effective theory (HQET) for the operators involving one effective heavy quark and light degrees of freedom are completely integrable in some cases and are related to spin chain models with the Hamiltonian commuting with the nondiagonal entry C( u) of the monodromy matrix. In this work we provide a more complete mathematical treatment of such spin chains in the QISM framework. We also discuss the relation of integrable models that appear in the HQET context with the large-spin limit of integrable models in QCD with light quarks. We find that the conserved charges and the "ground state" wave functions in HQET models can be obtained from the light-quark counterparts in a certain scaling limit.

Lattice dynamics and thermal transport in multiferroic CuCrO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, Dipanshu; Niedziela, Jennifer L.; May, Andrew F.

Inelastic neutron and x-ray scattering measurements of phonons and spin waves in CuCrO 2 were performed over a wide range of temperature, and complemented with first-principles simulations. The phonon dispersions and density of states are well reproduced by our density functional cal- culations, and reveal a strong anisotropy of Cu vibrations, with large amplitudes of low-frequency in-plane motions. In addition, we find that spin fluctuations persist above 300 K, far above the N eel temperature for long-range antiferromagnetic order, TN. Modeling of the thermal conductivity, based on our phonon measurements and simulations, reveals a significant anisotropy and indicates that themore » spin fluctuations above TN constitute a strong source of phonon scattering.« less

Lattice dynamics and thermal transport in multiferroic CuCrO 2

DOE PAGES

Bansal, Dipanshu; Niedziela, Jennifer L.; May, Andrew F.; ...

2017-02-09

Inelastic neutron and x-ray scattering measurements of phonons and spin waves in CuCrO 2 were performed over a wide range of temperature, and complemented with first-principles simulations. The phonon dispersions and density of states are well reproduced by our density functional cal- culations, and reveal a strong anisotropy of Cu vibrations, with large amplitudes of low-frequency in-plane motions. In addition, we find that spin fluctuations persist above 300 K, far above the N eel temperature for long-range antiferromagnetic order, TN. Modeling of the thermal conductivity, based on our phonon measurements and simulations, reveals a significant anisotropy and indicates that themore » spin fluctuations above TN constitute a strong source of phonon scattering.« less

Effects of Accretion Disks on Spins and Eccentricities of Binaries, and Implications for Gravitational Waves

NASA Technical Reports Server (NTRS)

Baker, John

2012-01-01

Effects of accretion disks on spins and eccentricities of binaries, and implications for gravitational waves. John Baker Space-based gravitational wave observations will allow exquisitely precise measurements of massive black hole binary properties. Through several recently suggested processes, these properties may depend on interactions with accretion disks through the merger process. I will discuss ways that accretion may influence those binary properties which may be probed by gravitational-wave observations.

Gravitational wave emission from oscillating millisecond pulsars

NASA Astrophysics Data System (ADS)

Alford, Mark G.; Schwenzer, Kai

2015-02-01

Neutron stars undergoing r-mode oscillation emit gravitational radiation that might be detected on the Earth. For known millisecond pulsars the observed spin-down rate imposes an upper limit on the possible gravitational wave signal of these sources. Taking into account the physics of r-mode evolution, we show that only sources spinning at frequencies above a few hundred Hertz can be unstable to r-modes, and we derive a more stringent universal r-mode spin-down limit on their gravitational wave signal. We find that this refined bound limits the gravitational wave strain from millisecond pulsars to values below the detection sensitivity of next generation detectors. Young sources are therefore a more promising option for the detection of gravitational waves emitted by r-modes and to probe the interior composition of compact stars in the near future.

Excitations of breathers and rogue wave in the Heisenberg spin chain

NASA Astrophysics Data System (ADS)

Qi, Jian-Wen; Duan, Liang; Yang, Zhan-Ying; Yang, Wen-Li

2018-01-01

We study the excitations of breathers and rogue wave in a classical Heisenberg spin chain with twist interaction, which is governed by a fourth-order integrable nonlinear Schrödinger equation. The dynamics of these waves have been extracted from an exact solution. In particular, the corresponding existence conditions based on the parameters of perturbation wave number K, magnon number N, background wave vector ks and amplitude c are presented explicitly. Furthermore, the characteristics of magnetic moment distribution corresponding to these nonlinear waves are also investigated in detail. Finally, we discussed the state transition of three types nonlinear localized waves under the different excitation conditions.

Out-of-equilibrium dynamics of photoexcited spin-state concentration waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marino, Andrea; Buron-Le Cointe, M.; Lorenc, M.

2015-01-28

The spin crossover compound [Fe IIH 2L 2-Me][PF 6]2 presents a two-step phase transition. In the intermediate phase, a spin state concentration wave (SSCW) appears resulting from a symmetry breaking (cell doubling) associated with a long-range order of alternating high and low spin molecular states. Lastly, by combining time-resolved optical and X-ray diffraction measurements on a single crystal, we study how such a system responds to femtosecond laser excitation and we follow in real time the erasing and rewriting of the SSCW

Magnonic analog of relativistic Zitterbewegung in an antiferromagnetic spin chain

NASA Astrophysics Data System (ADS)

Wang, Weiwei; Gu, Chenjie; Zhou, Yan; Fangohr, Hans

2017-07-01

We theoretically investigate the spin-wave (magnon) excitations in a classical antiferromagnetic spin chain with easy-axis anisotropy. We obtain a Dirac-like equation by linearizing the Landau-Lifshitz-Gilbert equation in this antiferromagnetic system, in contrast to the ferromagnetic system in which a Schrödinger-type equation is derived. The Hamiltonian operator in the Dirac-like equation is a pseudo-Hermitian. We compute and demonstrate relativistic Zitterbewegung (trembling motion) in the antiferromagnetic spin chain by measuring the expectation values of the wave-packet position.

Identical spin rotation effect and electron spin waves in quantum gas of atomic hydrogen

NASA Astrophysics Data System (ADS)

Lehtonen, L.; Vainio, O.; Ahokas, J.; Järvinen, J.; Novotny, S.; Sheludyakov, S.; Suominen, K.-A.; Vasiliev, S.; Khmelenko, V. V.; Lee, D. M.

2018-05-01

We present an experimental study of electron spin waves in atomic hydrogen gas compressed to high densities of ∼5 × 1018 cm‑3 at temperatures ranging from 0.26 to 0.6 K in the strong magnetic field of 4.6 T. Hydrogen gas is in a quantum regime when the thermal de-Broglie wavelength is much larger than the s-wave scattering length. In this regime the identical particle effects play a major role in atomic collisions and lead to the identical spin rotation effect (ISR). We observed a variety of spin wave modes caused by this effect with strong dependence on the magnetic potential caused by variations of the polarizing magnetic field. We demonstrate confinement of the ISR modes in the magnetic potential and manipulate their properties by changing the spatial profile of the magnetic field. We have found that at a high enough density of H gas the magnons accumulate in their ground state in the magnetic trap and exhibit long coherence, which has a profound effect on the electron spin resonance spectra. Such macroscopic accumulation of the ground state occurs at a certain critical density of hydrogen gas, where the chemical potential of the magnons becomes equal to the energy of their ground state in the trapping potential.

An Analysis of Characteristics of Magnetostatic Waves Propagating in Nonhomogeneous Fields Across the Ferrospinel Film Thickness

NASA Astrophysics Data System (ADS)

Velikanova, Yu. V.; Vinogradova, M. R.; Mitlina, L. A.

2018-06-01

The amplitude-frequency characteristics (AFCs) of magnetostatic waves in the films of magnesium-manganese ferrospinels with nanostructured inhomogeneities are discussed. A common effect, observed in the film AFCs under different process conditions, is the `oscillations of propagation' of magnetostatic waves as a function of the frequency. The oscillation pattern is thought to depend on the inhomogeneous exchange parameters and the surface anisotropy constants. The wave instability is characterized by the resonant interaction of the dipole magnetostatic waves with the surface spin waves. It is shown that the ferrospinel films with periodic nanostructured inhomogeneities of 30-40 nm could be treated as magnon crystals. An inclusion of the inhomogeneity into consideration allows one to provide reasoning for the formation of the rejection bands within the range 9-12 GHz, whose frequencies correspond to Bragg frequencies.

Generator Coordinate Method Analysis of Xe and Ba Isotopes

NASA Astrophysics Data System (ADS)

Higashiyama, Koji; Yoshinaga, Naotaka; Teruya, Eri

Nuclear structure of Xe and Ba isotopes is studied in terms of the quantum-number projected generator coordinate method (GCM). The GCM reproduces well the energy levels of high-spin states as well as low-lying states. The structure of the low-lying states is analyzed through the GCM wave functions.

The magnetic particle in a box: Analytic and micromagnetic analysis of probe-localized spin wave modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adur, Rohan, E-mail: adur@physics.osu.edu; Du, Chunhui; Manuilov, Sergei A.

2015-05-07

The dipole field from a probe magnet can be used to localize a discrete spectrum of standing spin wave modes in a continuous ferromagnetic thin film without lithographic modification to the film. Obtaining the resonance field for a localized mode is not trivial due to the effect of the confined and inhomogeneous magnetization precession. We compare the results of micromagnetic and analytic methods to find the resonance field of localized modes in a ferromagnetic thin film, and investigate the accuracy of these methods by comparing with a numerical minimization technique that assumes Bessel function modes with pinned boundary conditions. Wemore » find that the micromagnetic technique, while computationally more intensive, reveals that the true magnetization profiles of localized modes are similar to Bessel functions with gradually decaying dynamic magnetization at the mode edges. We also find that an analytic solution, which is simple to implement and computationally much faster than other methods, accurately describes the resonance field of localized modes when exchange fields are negligible, and demonstrating the accessibility of localized mode analysis.« less

Effects of pressure on the magnetic properties of FeO: A diffusion Monte Carlo study

NASA Astrophysics Data System (ADS)

Townsend, Joshua; Shulenburger, Luke; Mattsson, Thomas; Esler, Ken; Cohen, Ronald

While simple in terms of structure and composition, both experimental and computational investigations have demonstrated that FeO has a rich phase diagram of structural phase transformations, electronic spin transitions, insulator-metal transitions, and magnetic ordering transitions, due to the open-shell occupation of the Fe 3d electrons. We investigated the magnetic and electronic structures of FeO under ambient and high pressure conditions using diffusion Quantum Monte Carlo (QMC) within the fixed-node approximation. QMC techniques are especially well suited to the study of strongly correlated systems because they explicitly include correlation into the ground-state wave function. Here we report on the effects of the choice of trial wave function on the ambient pressure lattice distortion due to AFM ordering, as well as the equation of state, spin collapse, and metal-insulator transitions. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE.

Approximate spin projection of three-component UHF wavefunctions - The states of the pentachlorocyclopentadienyl cation and the croconate dianion, C5O5/2-/

NASA Technical Reports Server (NTRS)

Phillips, D. H.; Schug, J. C.

1974-01-01

The approximate spin projection method of Amos et al. is extended to handle UHF wave functions having three significant components of differing multiplicity. An expression is given for the energy after single annihilation which differs from that of Amos and Hall. The new expression reproduces the results obtained from a previous exact calculation for which the weights and energies of the components are known. The extended approximate projection method is applied to the pi-electron UHF wave functions for the ground states of the pentachlorocyclopentadienyl cation and the croconate dianion, C5O5(2-). The results indicate a triplet ground state for the former and a singlet ground state for the latter, in agreement with experimental ESR susceptibility measurements for these molecular ions. C5C15(-) cannont be treated by restricted Hartree-Fock theory, due to its open-shell ground state. Incorrect results are obtained for the croconate dianion, if restricted Hartree-Fock theory and singly excited configuration interactions are utilized.

The low-frequency continuum as observed in the solar wind from ISEE 3 - Thermal electrostatic noise

NASA Technical Reports Server (NTRS)

Hoang, S.; Steinberg, J.-L.; Epstein, G.; Tilloles, P.; Fainberg, J.; Stone, R. G.

1980-01-01

The low frequency continuum (LFC) noise between 30 and 200 kHz has been investigated from the ISEE 3 spacecraft in the solar wind by means of a radio astronomy experiment more sensitive than previously available. It is demonstrated that the LFC radiation observed in the solar wind is in the form of longitudinal plasma waves rather than transverse electromagnetic waves. The observed spectral characteristics are found to be a function of antenna length. In addition, both the absence of antenna spin modulation and the fact that these plasma waves do not propagate to large distances imply a local origin for the LFC.

Branching and resonant characteristics of surface plasma waves in a semi-bounded quantum plasma including spin-current effects

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Gwanyong; Jung, Young-Dae

2018-05-01

The dispersion relation for the waves propagating on the surface of a bounded quantum plasma with consideration of electron spin-current and ion-stream is derived and numerically investigated. We have found that one of the real parts of the wave frequency has the branching behavior beyond the instability domains. In such a region where the frequency branching occurs, the waves exhibit purely propagating mode. The resonant instability has also been investigated. We have found that when the phase velocity of the wave is close to the velocity of ion-stream the wave becomes unstable. However, the resonant growth rate is remarkably reduced by the effect of electron spin-current. The growth rate is also decreased by either the reduction of ion-stream velocity or the increase in quantum wavelength. Thus, the quantum effect in terms of the quantum wave number is found to suppress the resonant instability. It is also found that the increase in Fermi energy can reduce the growth rate of the resonant wave in the quantum plasma.

Superconducting states of topological surface states in β-PdBi2 investigated by STM/STS

NASA Astrophysics Data System (ADS)

Iwaya, Katsuya; Okawa, Kenjiro; Hanaguri, Tetsuo; Kohsaka, Yuhki; Machida, Tadashi; Sasagawa, Takao

We investigate superconducting (SC) states of topological surface states in β-PdBi2 using very low temperature STM. Characteristic quasiparticle interference patterns strongly support the existence of the spin-polarized surface states at the Fermi level in the normal state. A fully-opened SC gap well described by the conventional BCS model is observed, indicating the SC gap opening at the spin-polarized Fermi surfaces. Considering a possible mixing of odd- and even parity orbital functions in C4v group symmetry lowered from D4h near the surface, we suggest that the SC gap consists of the mixture of s- and p-wave SC gap functions in the two-dimensional state.

Light-front spin-dependent spectral function and nucleon momentum distributions for a three-body system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del Dotto, Alessio; Pace, Emanuele; Salme, Giovanni

Poincare covariant definitions for the spin-dependent spectral function and for the momentum distributions within the light-front Hamiltonian dynamics are proposed for a three-fermion bound system, starting from the light-front wave function of the system. The adopted approach is based on the Bakamjian–Thomas construction of the Poincaré generators, which allows one to easily import the familiar and wide knowledge on the nuclear interaction into a light-front framework. The proposed formalism can find useful applications in refined nuclear calculations, such as those needed for evaluating the European Muon Collaboration effect or the semi-inclusive deep inelastic cross sections with polarized nuclear targets, sincemore » remarkably the light-front unpolarized momentum distribution by definition fulfills both normalization and momentum sum rules. As a result, also shown is a straightforward generalization of the definition of the light-front spectral function to an A-nucleon system.« less

Light-front spin-dependent spectral function and nucleon momentum distributions for a three-body system

DOE PAGES

Del Dotto, Alessio; Pace, Emanuele; Salme, Giovanni; ...

2017-01-10

Poincare covariant definitions for the spin-dependent spectral function and for the momentum distributions within the light-front Hamiltonian dynamics are proposed for a three-fermion bound system, starting from the light-front wave function of the system. The adopted approach is based on the Bakamjian–Thomas construction of the Poincaré generators, which allows one to easily import the familiar and wide knowledge on the nuclear interaction into a light-front framework. The proposed formalism can find useful applications in refined nuclear calculations, such as those needed for evaluating the European Muon Collaboration effect or the semi-inclusive deep inelastic cross sections with polarized nuclear targets, sincemore » remarkably the light-front unpolarized momentum distribution by definition fulfills both normalization and momentum sum rules. As a result, also shown is a straightforward generalization of the definition of the light-front spectral function to an A-nucleon system.« less

Combined Molecular and Spin Dynamics Simulation of Lattice Vacancies in BCC Iron

NASA Astrophysics Data System (ADS)

Mudrick, Mark; Perera, Dilina; Eisenbach, Markus; Landau, David P.

Using an atomistic model that treats translational and spin degrees of freedom equally, combined molecular and spin dynamics simulations have been performed to study dynamic properties of BCC iron at varying levels of defect impurity. Atomic interactions are described by an empirical many-body potential, and spin interactions with a Heisenberg-like Hamiltonian with a coordinate dependent exchange interaction. Equations of motion are solved numerically using the second-order Suzuki-Trotter decomposition for the time evolution operator. We analyze the spatial and temporal correlation functions for atomic displacements and magnetic order to obtain the effect of vacancy defects on the phonon and magnon excitations. We show that vacancy clusters in the material cause splitting of the characteristic transverse spin-wave excitations, indicating the production of additional excitation modes. Additionally, we investigate the coupling of the atomic and magnetic modes. These modes become more distinct with increasing vacancy cluster size. This material is based upon work supported by the U.S. Department of Energy Office of Science Graduate Student Research (SCGSR) program.

Interactions in higher-spin gravity: a holographic perspective

NASA Astrophysics Data System (ADS)

Sleight, Charlotte

2017-09-01

This review is an elaboration of recent results on the holographic re-construction of metric-like interactions in higher-spin gauge theories on anti-de Sitter space (AdS), employing their conjectured duality with free conformal field theories (CFTs). After reviewing the general approach and establishing the necessary intermediate results, we extract explicit expressions for the complete cubic action on AdSd+1 and the quartic self-interaction of the scalar on AdS4 for the type A minimal bosonic higher-spin theory from the three- and four- point correlation functions of single-trace operators in the free scalar O(N) vector model. For this purpose tools were developed to evaluate tree-level three-point Witten diagrams involving totally symmetric fields of arbitrary integer spin and mass, and the conformal partial wave expansions of their tree-level four-point Witten diagrams. We also discuss the implications of the holographic duality on the locality properties of interactions in higher-spin gauge theories.

Influence of Molecular Oxygen on Ortho-Para Conversion of Water Molecules

NASA Astrophysics Data System (ADS)

Valiev, R. R.; Minaev, B. F.

2017-07-01

The mechanism of influence of molecular oxygen on the probability of ortho-para conversion of water molecules and its relation to water magnetization are considered within the framework of the concept of paramagnetic spin catalysis. Matrix elements of the hyperfine ortho-para interaction via the Fermi contact mechanism are calculated, as well as the Maliken spin densities on water protons in H2O and O2 collisional complexes. The mechanism of penetration of the electron spin density into the water molecule due to partial spin transfer from paramagnetic oxygen is considered. The probability of ortho-para conversion of the water molecules is estimated by the quantum chemistry methods. The results obtained show that effective ortho-para conversion of the water molecules is possible during the existence of water-oxygen dimers. An external magnetic field affects the ortho-para conversion rate given that the wave functions of nuclear spin sublevels of the water protons are mixed in the complex with oxygen.

SUSANS With Polarized Neutrons.

PubMed

Wagh, Apoorva G; Rakhecha, Veer Chand; Strobl, Makus; Treimer, Wolfgang

2005-01-01

Super Ultra-Small Angle Neutron Scattering (SUSANS) studies over wave vector transfers of 10(-4) nm(-1) to 10(-3) nm(-1) afford information on micrometer-size agglomerates in samples. Using a right-angled magnetic air prism, we have achieved a separation of ≈10 arcsec between ≈2 arcsec wide up- and down-spin peaks of 0.54 nm neutrons. The SUSANS instrument has thus been equipped with the polarized neutron option. The samples are placed in a uniform vertical field of 8.8 × 10(4) A/m (1.1 kOe). Several magnetic alloy ribbon samples broaden the up-spin neutron peak significantly over the ±1.3 × 10(-3) nm(-1) range, while leaving the down-spin peak essentially unaltered. Fourier transforms of these SUSANS spectra corrected for the instrument resolution, yield micrometer-range pair distribution functions for up- and down-spin neutrons as well as the nuclear and magnetic scattering length density distributions in the samples.

The unrestricted Hartree-Fock self consistent field calculation for spin density wave state in metallic carbon nanotube

NASA Astrophysics Data System (ADS)

Kobayashi, Katsushi

1997-06-01

The possibility of a spin density wave (SDW) state in a metallic carbon nanotube (CN) and its electronic properties are investigated within the Hartree-Fock self consistent field (SCF) energy-band calculation. Two kinds of spatial SDW states are assumed in this study. Each assumed SDW on the wave function is constructed with the degenerate π orbital in the metallic CN system. The results calculated for the one SDW model of CN always have a relative stability (˜ 0.1 eV/cell) in SCF total energy compared with the original model in which no SDW is assumed. All the results calculated for another SDW model are completely equal to the original one. Moreover, in the energy dispersion of the former stable SDW model, the degenerate π level found in the original model disappears and the band gap (3-5 eV) occurs around at the Fermi level. The energetic stability and the band gap are also found in the π-electron band calculation within the Hubbard Hamiltonian.

Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

PubMed

El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

2017-06-26

Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot

NASA Astrophysics Data System (ADS)

Ware, M. E.; Stinaff, E. A.; Gammon, D.; Doty, M. F.; Bracker, A. S.; Gershoni, D.; Korenev, V. L.; Bădescu, Ş. C.; Lyanda-Geller, Y.; Reinecke, T. L.

2005-10-01

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

Analytical recursive method to ascertain multisite entanglement in doped quantum spin ladders

NASA Astrophysics Data System (ADS)

Roy, Sudipto Singha; Dhar, Himadri Shekhar; Rakshit, Debraj; SenDe, Aditi; Sen, Ujjwal

2017-08-01

We formulate an analytical recursive method to generate the wave function of doped short-range resonating valence bond (RVB) states as a tool to efficiently estimate multisite entanglement as well as other physical quantities in doped quantum spin ladders. We prove that doped RVB ladder states are always genuine multipartite entangled. Importantly, our results show that within specific doping concentration and model parameter regimes, the doped RVB state essentially characterizes the trends of genuine multiparty entanglement in the exact ground states of the Hubbard model with large on-site interactions, in the limit that yields the t -J Hamiltonian.

Theory of disordered Heisenberg ferromagnets

NASA Technical Reports Server (NTRS)

Stubbs, R. M.

1973-01-01

A Green's function technique is used to calculate the magnetic properties of Heisenberg ferromagnets in which the exchange interactions deviate randomly in strength from the mean interaction. Systems of sc, bcc, and fcc topologies and of general spin values are treated. Disorder produces marked effects in the density of spin wave states, in the form of enhancement of the low-energy density and extension of the energy band to higher values. The spontaneous magnetization and the Curie temperature decrease with increasing disorder. The effects of disorder are shown to be more pronounced in the ferromagnetic than in the paramagnetic phase.

Approximate arbitrary κ-state solutions of Dirac equation with Schiöberg and Manning-Rosen potentials within the coulomb-like Yukawa-like and generalized tensor interactions

NASA Astrophysics Data System (ADS)

Ikot, Akpan N.; Hassanabadi, Hassan; Obong, Hillary Patrick; Mehraban, H.; Yazarloo, Bentol Hoda

2015-07-01

The effects of Coulomb-like tensor (CLT), Yukawa-like tensor (YLT) and generalized tensor (GLT) interactions are investigated in the Dirac theory with Schiöberg and Manning-Rosen potentials within the framework of spin and pseudospin symmetries using the Nikiforov-Uvarov method. The bound state energy spectra and the radial wave functions have been approximately obtained in the case of spin and pseudospin symmetries. We have also reported some numerical results and figures to show the effects these tensor interactions.

Simultaneous laser excitation of backward volume and perpendicular standing spin waves in full-Heusler Co2FeAl0.5Si0.5 films

PubMed Central

Chen, Zhifeng; Yan, Yong; Li, Shufa; Xu, Xiaoguang; Jiang, Yong; Lai, Tianshu

2017-01-01

Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed. The frequency of BVMSW mode does not obviously depend on the film thickness, but the lifetime and the effective damping appear to do so. The simultaneous excitation of BVMSW and PSSW in Heusler alloy films as well as the characterization of their dynamic behaviors may be of interest for magnonic and spintronic applications. PMID:28195160

Local NMR relaxation rates T1-1 and T2-1 depending on the d -vector symmetry in the vortex state of chiral and helical p -wave superconductors

NASA Astrophysics Data System (ADS)

Tanaka, Kenta K.; Ichioka, Masanori; Onari, Seiichiro

2018-04-01

Local NMR relaxation rates in the vortex state of chiral and helical p -wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate T1-1 and spin-spin relaxation rate T2-1. Depending on the relation between the NMR relaxation direction and the d -vector symmetry, the local T1-1 and T2-1 in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the d -vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency s -wave spin-triplet Cooper pairs. The difference between the local T1-1 and T2-1 in the site-selective NMR measurement is expected to be a method to examine the d -vector symmetry of candidate materials for spin-triplet superconductors.

Spin-wave stiffness in the Dzyaloshinskii-Moriya helimagnets Mn1 -xFexSi

NASA Astrophysics Data System (ADS)

Grigoriev, S. V.; Altynbaev, E. V.; Siegfried, S.-A.; Pschenichnyi, K. A.; Menzel, D.; Heinemann, A.; Chaboussant, G.

2018-01-01

The small-angle neutron scattering is used to measure the spin-wave stiffness in the field-polarized state of the Dzyaloshinskii-Moriya helimagnets Mn1 -xFexSi with x =0.03 , 0.06, 0.09, and 0.10. The Mn1 -xFexSi compounds are helically ordered below Tc and show a helical fluctuation regime above Tc in a wide range up to TDM. The critical temperatures Tc and TDM decrease with x and tend to 0 at x =0.11 and 0.17, respectively. We have found that the spin-wave stiffness A change weakly with temperature for each individual Fe-doped compound. On the other hand, the spin-wave stiffness A decreases with x duplicating the TDM dependence on x , rather than Tc(x ) . These findings classify the thermal phase transition in all Mn1 -xFexSi compounds as an abrupt change in the spin state caused, most probably, by the features of an electronic band structure. Moreover, the criticality in these compounds is not related to the value of the ferromagnetic interaction but demonstrates the remarkable role of the Dzyaloshinskii-Moriya interaction as a factor destabilizing the magnetic order.

Spin waves, vortices, fermions, and duality in the Ising and Baxter models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogilvie, M.C.

1981-10-15

Field-theoretic methods are applied to a number of two-dimensional lattice models with Abelian symmetry groups. It is shown, using a vortex+spin-wave decomposition, that the Z/sub p/-Villain models are related to a class of continuum field theories with analogous duality properties. Fermion operators for these field theories are discussed. In the case of the Ising model, the vortices and spin-waves conspire to produce a free, massive Majorana field theory in the continuum limit. The continuum limit of the Baxter model is also studied, and the recent results of Kadanoff and Brown are rederived and extended.

Observation of spin waves in Pd(1. 5% Fe). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynn, J.W.; Rhyne, J.J.; Budnick, J.I.

1982-01-01

Inelastic neutron scattering measurements have been carried out on the giant-moment alloy system Pd(1.5% Fe), which is in the dilute ferromagnetic regime. Below the Curie temperature of 67K, relatively well-defined spin-wave excitations have been observed in the small wavevector region (Q < 0.14/A). The dispersion of these excitations is consistent with the quadratic relation E = D(Q/sup 2/) expected for an isotropic ferromagnet, with D = 40 meV-(A/sup 2/) at a temperature of the 40K. With increasing temperature, the spin waves are found to renormalize in energy, and broaden rapidly both with increasing Q and increasing temperature.

Neutron Resonance Spin Determination Using Multi-Segmented Detector DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baramsai, B.; Mitchell, G. E.; Chyzh, A.

2011-06-01

A sensitive method to determine the spin of neutron resonances is introduced based on the statistical pattern recognition technique. The new method was used to assign the spins of s-wave resonances in {sup 155}Gd. The experimental neutron capture data for these nuclei were measured with the DANCE (Detector for Advanced Neutron Capture Experiment) calorimeter at the Los Alamos Neutron Science Center. The highly segmented calorimeter provided detailed multiplicity distributions of the capture {gamma}-rays. Using this information, the spins of the neutron capture resonances were determined. With these new spin assignments, level spacings are determined separately for s-wave resonances with J{supmore » {pi}} = 1{sup -} and 2{sup -}.« less

Surface magnetism in a chiral d -wave superconductor with hexagonal symmetry

NASA Astrophysics Data System (ADS)

Goryo, Jun; Imai, Yoshiki; Rui, W. B.; Sigrist, Manfred; Schnyder, Andreas P.

2017-10-01

Surface properties are examined in a chiral d -wave superconductor with hexagonal symmetry, whose one-body Hamiltonian possesses intrinsic spin-orbit coupling identical to the one characterizing the topological nature of the Kane-Mele honeycomb insulator. In the normal state, spin-orbit coupling gives rise to spontaneous surface spin currents, whereas in the superconducting state, besides the spin currents, there exist also charge surface currents, due to chiral pairing symmetry. Interestingly, the combination of these two currents results in a surface spin polarization, whose spatial dependence is markedly different on the zigzag and armchair surfaces. We discuss various potential candidate materials, such as SrPtAs, which may exhibit these surface properties.

Current-induced spin wave Doppler shift

NASA Astrophysics Data System (ADS)

Bailleul, Matthieu

2010-03-01

In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

Co- and contra-directional vertical coupling between ferromagnetic layers with grating for short-wavelength spin wave generation

NASA Astrophysics Data System (ADS)

Graczyk, Piotr; Zelent, Mateusz; Krawczyk, Maciej

2018-05-01

The possibility to generate short spin waves (SWs) is of great interest in the field of magnonics nowadays. We present an effective and technically affordable way of conversion of long SWs, which may be generated by conventional microwave antenna, to the short, sub-micrometer waves. It is achieved by grating-assisted resonant dynamic dipolar interaction between two ferromagnetic layers separated by some distance. We analyze criteria for the optimal conversion giving a semi-analytical approach for the coupling coefficient. We show by the numerical calculations the efficient energy transfer between layers which may be either of co-directional or contra-directional type. Such a system may operate either as a short spin wave generator or a frequency filter, moving forward possible application of magnonics.

Lattice Waves, Spin Waves, and Neutron Scattering

DOE R&D Accomplishments Database

Brockhouse, Bertram N.

1962-03-01

Use of neutron inelastic scattering to study the forces between atoms in solids is treated. One-phonon processes and lattice vibrations are discussed, and experiments that verified the existence of the quantum of lattice vibrations, the phonon, are reviewed. Dispersion curves, phonon frequencies and absorption, and models for dispersion calculations are discussed. Experiments on the crystal dynamics of metals are examined. Dispersion curves are presented and analyzed; theory of lattice dynamics is considered; effects of Fermi surfaces on dispersion curves; electron-phonon interactions, electronic structure influence on lattice vibrations, and phonon lifetimes are explored. The dispersion relation of spin waves in crystals and experiments in which dispersion curves for spin waves in Co-Fe alloy and magnons in magnetite were obtained and the reality of the magnon was demonstrated are discussed. (D.C.W)

Initial data for black hole-neutron star binaries, with rotating stars

NASA Astrophysics Data System (ADS)

Tacik, Nick; Foucart, Francois; Pfeiffer, Harald P.; Muhlberger, Curran; Kidder, Lawrence E.; Scheel, Mark A.; Szilágyi, Béla

2016-11-01

The coalescence of a neutron star with a black hole is a primary science target of ground-based gravitational wave detectors. Constraining or measuring the neutron star spin directly from gravitational wave observations requires knowledge of the dependence of the emission properties of these systems on the neutron star spin. This paper lays foundations for this task, by developing a numerical method to construct initial data for black hole-neutron star binaries with arbitrary spin on the neutron star. We demonstrate the robustness of the code by constructing initial-data sets in large regions of the parameter space. In addition to varying the neutron star spin-magnitude and spin-direction, we also explore neutron star compactness, mass-ratio, black hole spin, and black hole spin-direction. Specifically, we are able to construct initial data sets with neutron stars spinning near centrifugal break-up, and with black hole spins as large as {S}{BH}/{M}{BH}2=0.99.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gergely, Laszlo Arpad; Department of Experimental Physics, University of Szeged, Dom ter 9, Szeged 6720; Department of Applied Science, London South Bank University, 103 Borough Road, London SE1 0AA

We give here a new third post-Newtonian (3PN) spin-spin contribution (in the PN parameter {epsilon}) to the accumulated orbital phase of a compact binary, arising from the spin-orbit precessional motion of the spins. In the equal mass case, this contribution vanishes, but Laser Interferometer Space Antenna (LISA) sources of merging supermassive binary black holes have typically a mass ratio of 1:10. For such nonequal masses, this 3PN correction is periodic in time, with a period approximately {epsilon}{sup -1} times larger than the period of gravitational waves. We derive a renormalized and simpler expression of the spin-spin coefficient at 2PN, asmore » an average over the time scale of this period of the combined 2PN and 3PN contribution. We also find that for LISA sources the quadrupole-monopole contribution to the phase dominates over the spin-spin contribution, while the self-spin contribution is negligible even for the dominant spin. Finally, we define a renormalized total spin coefficient {sigma} to be employed in the search for gravitational waves emitted by LISA sources.« less

Sivers and cos 2 ϕ asymmetries in semi-inclusive deep inelastic scattering in light-front holographic model

NASA Astrophysics Data System (ADS)

Maji, Tanmay; Chakrabarti, Dipankar; Mukherjee, Asmita

2018-01-01

The spin asymmetries in SIDIS associated with T -odd TMDs are presented in a light-front quark-diquark model of a proton. To incorporate the effects of the final-state interaction, the light front wave functions are modified to have a phase factor which is essential to have Sivers or Boer-Mulders functions. The Sivers and Boer-Mulder asymmetries are compared with HERMES and COMPASS data.

Analytic gravitational waveforms for generic precessing compact binaries

NASA Astrophysics Data System (ADS)

Chatziioannou, Katerina; Klein, Antoine; Cornish, Neil; Yunes, Nicolas

2017-01-01

Gravitational waves from compact binaries are subject to amplitude and phase modulations arising from interactions between the angular momenta of the system. Failure to account for such spin-precession effects in gravitational wave data analysis could hinder detection and completely ruin parameter estimation. In this talk I will describe the construction of closed-form, frequency-domain waveforms for fully-precessing, quasi-circular binary inspirals. The resulting waveforms can model spinning binaries of arbitrary spin magnitudes, spin orientations, and masses during the inspiral phase. I will also describe ongoing efforts to extend these inspiral waveforms to the merger and ringdown phases.

High-temperature charge density wave correlations in La 1.875Ba 0.125CuO 4 without spin–charge locking

DOE PAGES

Miao, H.; Lorenzana, J.; Seibold, G.; ...

2017-11-07

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La 1.875Ba 0.125CuO 4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. Thismore » indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates.« less

Exotic superconductivity with enhanced energy scales in materials with three band crossings

NASA Astrophysics Data System (ADS)

Lin, Yu-Ping; Nandkishore, Rahul M.

2018-04-01

Three band crossings can arise in three-dimensional quantum materials with certain space group symmetries. The low energy Hamiltonian supports spin one fermions and a flat band. We study the pairing problem in this setting. We write down a minimal BCS Hamiltonian and decompose it into spin-orbit coupled irreducible pairing channels. We then solve the resulting gap equations in channels with zero total angular momentum. We find that in the s-wave spin singlet channel (and also in an unusual d-wave `spin quintet' channel), superconductivity is enormously enhanced, with a possibility for the critical temperature to be linear in interaction strength. Meanwhile, in the p-wave spin triplet channel, the superconductivity exhibits features of conventional BCS theory due to the absence of flat band pairing. Three band crossings thus represent an exciting new platform for realizing exotic superconducting states with enhanced energy scales. We also discuss the effects of doping, nonzero temperature, and of retaining additional terms in the k .p expansion of the Hamiltonian.

Irreversible Markov chains in spin models: Topological excitations

NASA Astrophysics Data System (ADS)

Lei, Ze; Krauth, Werner

2018-01-01

We analyze the convergence of the irreversible event-chain Monte Carlo algorithm for continuous spin models in the presence of topological excitations. In the two-dimensional XY model, we show that the local nature of the Markov-chain dynamics leads to slow decay of vortex-antivortex correlations while spin waves decorrelate very quickly. Using a Fréchet description of the maximum vortex-antivortex distance, we quantify the contributions of topological excitations to the equilibrium correlations, and show that they vary from a dynamical critical exponent z∼ 2 at the critical temperature to z∼ 0 in the limit of zero temperature. We confirm the event-chain algorithm's fast relaxation (corresponding to z = 0) of spin waves in the harmonic approximation to the XY model. Mixing times (describing the approach towards equilibrium from the least favorable initial state) however remain much larger than equilibrium correlation times at low temperatures. We also describe the respective influence of topological monopole-antimonopole excitations and of spin waves on the event-chain dynamics in the three-dimensional Heisenberg model.

High-temperature charge density wave correlations in La 1.875Ba 0.125CuO 4 without spin–charge locking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, H.; Lorenzana, J.; Seibold, G.

Although all superconducting cuprates display charge-ordering tendencies, their low-temperature properties are distinct, impeding efforts to understand the phenomena within a single conceptual framework. While some systems exhibit stripes of charge and spin, with a locked periodicity, others host charge density waves (CDWs) without any obviously related spin order. Here we use resonant inelastic X-ray scattering to follow the evolution of charge correlations in the canonical stripe-ordered cuprate La 1.875Ba 0.125CuO 4 across its ordering transition. We find that high-temperature charge correlations are unlocked from the wavevector of the spin correlations, signaling analogies to CDW phases in various other cuprates. Thismore » indicates that stripe order at low temperatures is stabilized by the coupling of otherwise independent charge and spin density waves, with important implications for the relation between charge and spin correlations in the cuprates.« less

Floquet spin states in graphene under ac-driven spin-orbit interaction

NASA Astrophysics Data System (ADS)

López, A.; Sun, Z. Z.; Schliemann, J.

2012-05-01

We study the role of periodically driven time-dependent Rashba spin-orbit coupling (RSOC) on a monolayer graphene sample. After recasting the originally 4×4 system of dynamical equations as two time-reversal related two-level problems, the quasienergy spectrum and the related dynamics are investigated via various techniques and approximations. In the static case, the system is gapped at the Dirac point. The rotating wave approximation (RWA) applied to the driven system unphysically preserves this feature, while the Magnus-Floquet approach as well as a numerically exact evaluation of the Floquet equation show that this gap is dynamically closed. In addition, a sizable oscillating pattern of the out-of-plane spin polarization is found in the driven case for states that are completely unpolarized in the static limit. Evaluation of the autocorrelation function shows that the original uniform interference pattern corresponding to time-independent RSOC gets distorted. The resulting structure can be qualitatively explained as a consequence of the transitions induced by the ac driving among the static eigenstates, i.e., these transitions modulate the relative phases that add up to give the quantum revivals of the autocorrelation function. Contrary to the static case, in the driven scenario, quantum revivals (suppressions) are correlated to spin-up (down) phases.

Unidirectional Spin-Wave-Propagation-Induced Seebeck Voltage in a PEDOT:PSS/YIG Bilayer

NASA Astrophysics Data System (ADS)

Wang, P.; Zhou, L. F.; Jiang, S. W.; Luan, Z. Z.; Shu, D. J.; Ding, H. F.; Wu, D.

2018-01-01

We clarify the physical origin of the dc voltage generation in a bilayer of a conducting polymer film and a micrometer-thick magnetic insulator Y3Fe5O12 (YIG) film under ferromagnetic resonance and/or spin wave excitation conditions. The previous attributed mechanism, the inverse spin Hall effect in the polymer [Nat. Mater. 12, 622 (2013), 10.1038/nmat3634], is excluded by two control experiments. We find an in-plane temperature gradient in YIG which has the same angular dependence with the generated voltage. Both vanish when the YIG thickness is reduced to a few nanometers. Thus, we argue that the dc voltage is governed by the Seebeck effect in the polymer, where the temperature gradient is created by the nonreciprocal magnetostatic surface spin wave propagation in YIG.

New technique for excitation of bulk and surface spin waves in ferromagnets

NASA Astrophysics Data System (ADS)

Bogacz, S. A.; Ketterson, J. B.

1985-09-01

A meander-line magnetic transducer is discussed in the context of bulk and surface spin-wave generation in ferromagnets. The magnetic field created by the transducer was calculated in closed analytic form for this model. The linear response of the ferromagnet to the inhomogenous surface disturbance of arbitrary ω and k was obtained as a self-consistent solution to the Bloch equation of motion and the Maxwell equations, subject to appropriate boundary condition. In particular, the energy flux through the boundary displays a sharp resonantlike absorption maximum concentrated at the frequency of the magnetostatic Damon-Eshbach (DE) surface mode; furthermore, the energy transfer spectrum is cut off abruptly below the threshold frequency of the bulk spin waves. The application of the meander line to the spin diffusion problem in NMR is also discussed.

Orbital Selective Spin Excitations and their Impact on Superconductivity of LiFe 1 - x Co x As

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yu; Yin, Zhiping; Wang, Xiancheng

We use neutron scattering to study spin excitations in single crystals of LiFe 0.88Co 0.12As, which is located near the boundary of the superconducting phase of LiFe 1-xCo xAs and exhibits non- Fermi-liquid behavior indicative of a quantum critical point. By comparing spin excitations of LiFe 0.88Co 0.12As with a combined density functional theory (DFT) and dynamical mean field theory (DMFT) calculation, we conclude that wave-vector correlated low energy spin excitations are mostly from the dxy orbitals, while high-energy spin excitations arise from the dyz and dxz orbitals. Unlike most iron pnictides, the strong orbital selective spin excitations in LiFeAsmore » family cannot be described by anisotropic Heisenberg Hamiltonian. While the evolution of low-energy spin excitations of LiFe 1-xCo xAs are consistent with electron-hole Fermi surface nesting condition for the dxy orbital, the reduced superconductivity in LiFe 0.88Co 0.12As suggests that Fermi surface nesting conditions for the dyz and dxz orbitals are also important for superconductivity in iron pnictides.« less

Orbital Selective Spin Excitations and their Impact on Superconductivity of LiFe 1 - x Co x As

DOE PAGES

Li, Yu; Yin, Zhiping; Wang, Xiancheng; ...

2016-06-17

We use neutron scattering to study spin excitations in single crystals of LiFe 0.88Co 0.12As, which is located near the boundary of the superconducting phase of LiFe 1-xCo xAs and exhibits non- Fermi-liquid behavior indicative of a quantum critical point. By comparing spin excitations of LiFe 0.88Co 0.12As with a combined density functional theory (DFT) and dynamical mean field theory (DMFT) calculation, we conclude that wave-vector correlated low energy spin excitations are mostly from the dxy orbitals, while high-energy spin excitations arise from the dyz and dxz orbitals. Unlike most iron pnictides, the strong orbital selective spin excitations in LiFeAsmore » family cannot be described by anisotropic Heisenberg Hamiltonian. While the evolution of low-energy spin excitations of LiFe 1-xCo xAs are consistent with electron-hole Fermi surface nesting condition for the dxy orbital, the reduced superconductivity in LiFe 0.88Co 0.12As suggests that Fermi surface nesting conditions for the dyz and dxz orbitals are also important for superconductivity in iron pnictides.« less

Entangled spin chain

NASA Astrophysics Data System (ADS)

Salberger, Olof; Korepin, Vladimir

We introduce a new model of interacting spin 1/2. It describes interactions of three nearest neighbors. The Hamiltonian can be expressed in terms of Fredkin gates. The Fredkin gate (also known as the controlled swap gate) is a computational circuit suitable for reversible computing. Our construction generalizes the model presented by Peter Shor and Ramis Movassagh to half-integer spins. Our model can be solved by means of Catalan combinatorics in the form of random walks on the upper half plane of a square lattice (Dyck walks). Each Dyck path can be mapped on a wave function of spins. The ground state is an equally weighted superposition of Dyck walks (instead of Motzkin walks). We can also express it as a matrix product state. We further construct a model of interacting spins 3/2 and greater half-integer spins. The models with higher spins require coloring of Dyck walks. We construct a SU(k) symmetric model (where k is the number of colors). The leading term of the entanglement entropy is then proportional to the square root of the length of the lattice (like in the Shor-Movassagh model). The gap closes as a high power of the length of the lattice [5, 11].

Orbital Selective Spin Excitations and their Impact on Superconductivity of LiFe_{1-x}Co_{x}As.

PubMed

Li, Yu; Yin, Zhiping; Wang, Xiancheng; Tam, David W; Abernathy, D L; Podlesnyak, A; Zhang, Chenglin; Wang, Meng; Xing, Lingyi; Jin, Changqing; Haule, Kristjan; Kotliar, Gabriel; Maier, Thomas A; Dai, Pengcheng

2016-06-17

We use neutron scattering to study spin excitations in single crystals of LiFe_{0.88}Co_{0.12}As, which is located near the boundary of the superconducting phase of LiFe_{1-x}Co_{x}As and exhibits non-Fermi-liquid behavior indicative of a quantum critical point. By comparing spin excitations of LiFe_{0.88}Co_{0.12}As with a combined density functional theory and dynamical mean field theory calculation, we conclude that wave-vector correlated low energy spin excitations are mostly from the d_{xy} orbitals, while high-energy spin excitations arise from the d_{yz} and d_{xz} orbitals. Unlike most iron pnictides, the strong orbital selective spin excitations in the LiFeAs family cannot be described by an anisotropic Heisenberg Hamiltonian. While the evolution of low-energy spin excitations of LiFe_{1-x}Co_{x}As is consistent with the electron-hole Fermi surface nesting conditions for the d_{xy} orbital, the reduced superconductivity in LiFe_{0.88}Co_{0.12}As suggests that Fermi surface nesting conditions for the d_{yz} and d_{xz} orbitals are also important for superconductivity in iron pnictides.

A Definition of the Magnetic Transition Temperature Using Valence Bond Theory.

PubMed

Jornet-Somoza, Joaquim; Deumal, Mercè; Borge, Juan; Robb, Michael A

2018-03-01

Macroscopic magnetic properties are analyzed using Valence Bond theory. Commonly the critical temperature T C for magnetic systems is associated with a maximum in the energy-based heat capacity C p (T). Here a more broadly applicable definition of the magnetic transition temperature T C is described using the spin moment expectation value (i.e., applying the spin exchange density operator) instead of energy. Namely, the magnetic capacity C s (T) reflects variation in the spin multiplicity as a function of temperature, which is shown to be related to ∂[χT(T)]/∂T. Magnetic capacity C s (T) depends on long-range spin interactions that are not relevant in the energy-based heat capacity C p (T). Differences between C s (T) and C p (T) are shown to be due to spin order/disorder within the crystal that can be monitored via a Valence Bond analysis of the corresponding magnetic wave function. Indeed the concept of the Boltzmann spin-alignment order is used to provide information about the spin correlation between magnetic units. As a final illustration, the critical temperature is derived from the magnetic capacity for several molecular magnets presenting different magnetic topologies that have been experimentally studied. A systematic shift between the transition temperatures associated with C s (T) and C p (T) is observed. It is demonstrated that this shift can be attributed to the loss of long-range spin correlation. This suggests that the magnetic capacity C s (T) can be used as a predictive tool for the magnetic topology and thus for the synthetic chemists.

Temperature-dependent relaxation of dipole-exchange magnons in yttrium iron garnet films

NASA Astrophysics Data System (ADS)

Mihalceanu, Laura; Vasyuchka, Vitaliy I.; Bozhko, Dmytro A.; Langner, Thomas; Nechiporuk, Alexey Yu.; Romanyuk, Vladyslav F.; Hillebrands, Burkard; Serga, Alexander A.

2018-06-01

Low-energy consumption enabled by charge-free information transport, which is free from Joule heating, and the ability to process phase-encoded data through the use of nanometer-sized interference devices operating at GHz and THz frequencies are just a few benefits of spin-wave-based technologies. Moreover, when approaching cryogenic temperatures, quantum phenomena in spin-wave systems pave the path towards quantum information processing. In view of these applications, the lifetime of magnons—spin-wave quanta—is of high relevance for the fields of magnonics, magnon spintronics, and quantum computing. Here, the relaxation behavior of parametrically excited magnons having wave numbers from zero up to 6 ×105rad cm-1 was experimentally investigated in the temperature range from 20 to 340 K in single-crystal yttrium iron garnet (YIG) films of different thickness epitaxially grown on gallium gadolinium garnet (GGG) substrates as well as in a bulk YIG crystal—the magnonic materials featuring the lowest magnetic damping thus far known. Due to magnon-magnon interactions, the relaxation rate of the parametric magnons increases with an increase of their wave numbers. In the thinner samples, this increase is less pronounced, which can be associated with a stronger quantization of their magnon spectra. For the YIG films, we have found a significant increase in the magnon relaxation rate below 150 K—up to eight times the reference value at 340 K—in the entire range of probed wave numbers, which is in direct opposition to that in ultrapure YIG crystals. This increase is related to rare-earth impurities contaminating the YIG samples with a slight contribution caused by the coupling of spin waves to the spin system of the paramagnetic GGG substrate at the lowest temperatures.

Development of a spinning wave heat engine

NASA Technical Reports Server (NTRS)

Zinn, B. T.; Powell, E. A.; Hubbartt, J. E.

1982-01-01

A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.

Wigner molecules: the strong-correlation limit of the three-electron harmonium.

PubMed

Cioslowski, Jerzy; Pernal, Katarzyna

2006-08-14

At the strong-correlation limit, electronic states of the three-electron harmonium atom are described by asymptotically exact wave functions given by products of distinct Slater determinants and a common Gaussian factor that involves interelectron distances and the center-of-mass position. The Slater determinants specify the angular dependence and the permutational symmetry of the wave functions. As the confinement strength becomes infinitesimally small, the states of different spin multiplicities become degenerate, their limiting energy reflecting harmonic vibrations of the electrons about their equilibrium positions. The corresponding electron densities are given by products of angular factors and a Gaussian function centered at the radius proportional to the interelectron distance at equilibrium. Thanks to the availability of both the energy and the electron density, the strong-correlation limit of the three-electron harmonium is well suited for testing of density functionals.

Quantum supersymmetric Bianchi IX cosmology

NASA Astrophysics Data System (ADS)

Damour, Thibault; Spindel, Philippe

2014-11-01

We study the quantum dynamics of a supersymmetric squashed three-sphere by dimensionally reducing (to one timelike dimension) the action of D =4 simple supergravity for a S U (2 ) -homogeneous (Bianchi IX) cosmological model. The quantization of the homogeneous gravitino field leads to a 64-dimensional fermionic Hilbert space. After imposition of the diffeomorphism constraints, the wave function of the Universe becomes a 64-component spinor of spin(8,4) depending on the three squashing parameters, which satisfies Dirac-like, and Klein-Gordon-like, wave equations describing the propagation of a "quantum spinning particle" reflecting off spin-dependent potential walls. The algebra of the supersymmetry constraints and of the Hamiltonian one is found to close. One finds that the quantum Hamiltonian is built from operators that generate a 64-dimensional representation of the (infinite-dimensional) maximally compact subalgebra of the rank-3 hyperbolic Kac-Moody algebra A E3 . The (quartic-in-fermions) squared-mass term μ^ 2 entering the Klein-Gordon-like equation has several remarkable properties: (i) it commutes with all the other (Kac-Moody-related) building blocks of the Hamiltonian; (ii) it is a quadratic function of the fermion number NF; and (iii) it is negative in most of the Hilbert space. The latter property leads to a possible quantum avoidance of the singularity ("cosmological bounce"), and suggests imposing the boundary condition that the wave function of the Universe vanish when the volume of space tends to zero (a type of boundary condition which looks like a final-state condition when considering the big crunch inside a black hole). The space of solutions is a mixture of "discrete-spectrum states" (parametrized by a few constant parameters, and known in explicit form) and of continuous-spectrum states (parametrized by arbitrary functions entering some initial-value problem). The predominantly negative values of the squared-mass term lead to a "bottle effect" between small-volume universes and large-volume ones, and to a possible reduction of the continuous spectrum to a discrete spectrum of quantum states looking like excited versions of the Planckian-size universes described by the discrete states at fermionic levels NF=0 and 1.

Ising tricriticality in the extended Hubbard model with bond dimerization

NASA Astrophysics Data System (ADS)

Fehske, Holger; Ejima, Satoshi; Lange, Florian; Essler, Fabian H. L.

We explore the quantum phase transition between Peierls and charge-density-wave insulating states in the one-dimensional, half-filled, extended Hubbard model with explicit bond dimerization. We show that the critical line of the continuous Ising transition terminates at a tricritical point, belonging to the universality class of the tricritical Ising model with central charge c=7/10. Above this point, the quantum phase transition becomes first order. Employing a numerical matrix-product-state based (infinite) density-matrix renormalization group method we determine the ground-state phase diagram, the spin and two-particle charge excitations gaps, and the entanglement properties of the model with high precision. Performing a bosonization analysis we can derive a field description of the transition region in terms of a triple sine-Gordon model. This allows us to derive field theory predictions for the power-law (exponential) decay of the density-density (spin-spin) and bond-order-wave correlation functions, which are found to be in excellent agreement with our numerical results. This work was supported by Deutsche Forschungsgemeinschaft (Germany), SFB 652, project B5, and by the EPSRC under Grant No. EP/N01930X/1 (FHLE).

Spontaneous symmetry breaking and electronic and dielectric properties in commensurate La7 /4Sr1 /4CuO4 and La5 /3Sr1 /3NiO4

NASA Astrophysics Data System (ADS)

Petersen, J.; Bechstedt, F.; Furthmüller, J.; Scolfaro, L. M.

2018-05-01

Complex ordered phases involving spin and charge degrees of freedom in condensed matter, such as layered cuprates and nickelates, are exciting but not well understood solid-state phenomena. The rich underlying physics of the overdoped high-temperature superconductor L a7 /4S r1 /4Cu O4 and colossal dielectric constant insulator L a5 /3S r1 /3Ni O4 is studied from first principles within density functional (perturbation) theory, including an effective Hubbard potential U for the exchange and correlation of d orbitals. Charge density wave (CDW) and spin density wave (SDW) orders are found in both materials, where the stripes are commensurate with the lattice. The SDWs are accompanied by complex antiferromagnetic spin arrangements along the stripes. The first series of conduction bands related to the pseudogap observed in the cuprate are found to be directly related to CDW order, while the colossal dielectric constant in the nickelate is demonstrated to be a result of vibronic coupling with CDW order. Differences between the two oxides are related to how the stripes fill with carriers.

Ab Initio Theory of Nuclear Magnetic Resonance Shifts in Metals

NASA Astrophysics Data System (ADS)

D'Avezac, Mayeul; Marzari, Nicola; Mauri, Francesco

2005-03-01

A comprehensive approach for the first-principles determination of all-electron NMR shifts in metallic systems is presented. Our formulation is based on a combination of density-functional perturbation theory and all-electron wavefunction reconstruction, starting from periodic-boundary calculations in the pseudopotential approximation. The orbital contribution to the NMR shift (the chemical shift) is obtained by combining the gauge-including projector augmented-wave approach (GIPAW), originally developed for the case of insulatorsootnotetextC. J. Pickard, Francesco Mauri, Phys. Rev. B, 63, 245101(2001), with the extension of linear-response theory to the case of metallic systemsootnotetextS. de Gironcoli, Phys. Rev. B, 51, 6773(1995). The spin contribution (the Knight shift) is obtained as a response to a finite uniform magnetic field, and through reconstructing the hyperfine interaction between the electron-spin density and the nuclear spins with the projector augmented-wave method (PAWootnotetextC. G. Van de Walle, P. E. Blöchl, Phys. Rev. B, 47, 4244(1993)). Our method is validated with applications to the case of the homogeneous electron gas and of simple metals. (Work supported by MURI grant DAAD 19-03-1-0169 and MIT-France)

Simple, explicitly time-dependent, and regular solutions of the linearized vacuum Einstein equations in Bondi-Sachs coordinates

NASA Astrophysics Data System (ADS)

Mädler, Thomas

2013-05-01

Perturbations of the linearized vacuum Einstein equations in the Bondi-Sachs formulation of general relativity can be derived from a single master function with spin weight two, which is related to the Weyl scalar Ψ0, and which is determined by a simple wave equation. By utilizing a standard spin representation of tensors on a sphere and two different approaches to solve the master equation, we are able to determine two simple and explicitly time-dependent solutions. Both solutions, of which one is asymptotically flat, comply with the regularity conditions at the vertex of the null cone. For the asymptotically flat solution we calculate the corresponding linearized perturbations, describing all multipoles of spin-2 waves that propagate on a Minkowskian background spacetime. We also analyze the asymptotic behavior of this solution at null infinity using a Penrose compactification and calculate the Weyl scalar Ψ4. Because of its simplicity, the asymptotically flat solution presented here is ideally suited for test bed calculations in the Bondi-Sachs formulation of numerical relativity. It may be considered as a sibling of the Bergmann-Sachs or Teukolsky-Rinne solutions, on spacelike hypersurfaces, for a metric adapted to null hypersurfaces.

Unconventional superconductivity in Y5Rh6Sn18 probed by muon spin relaxation

PubMed Central

Bhattacharyya, Amitava; Adroja, Devashibhai; Kase, Naoki; Hillier, Adrian; Akimitsu, Jun; Strydom, Andre

2015-01-01

Conventional superconductors are robust diamagnets that expel magnetic fields through the Meissner effect. It would therefore be unexpected if a superconducting ground state would support spontaneous magnetics fields. Such broken time-reversal symmetry states have been suggested for the high—temperature superconductors, but their identification remains experimentally controversial. We present magnetization, heat capacity, zero field and transverse field muon spin relaxation experiments on the recently discovered caged type superconductor Y5Rh6Sn18 ( TC= 3.0 K). The electronic heat capacity of Y5Rh6Sn18 shows a T3 dependence below Tc indicating an anisotropic superconducting gap with a point node. This result is in sharp contrast to that observed in the isostructural Lu5Rh6Sn18 which is a strong coupling s—wave superconductor. The temperature dependence of the deduced superfluid in density Y5Rh6Sn18 is consistent with a BCS s—wave gap function, while the zero-field muon spin relaxation measurements strongly evidences unconventional superconductivity through a spontaneous appearance of an internal magnetic field below the superconducting transition temperature, signifying that the superconducting state is categorized by the broken time-reversal symmetry. PMID:26286229

Simulation of Oscillatory Domain Wall Motion Driven by Spin Waves in Nanostrip with Perpendicular Magnetic Anisotropy

NASA Astrophysics Data System (ADS)

Lee, Shang Fan; Chang, Liang Juan; Spintronics Laboratory Team

2014-03-01

We numerically investigate the spin waves (SW) induced domain wall (DW) oscillatory motion in a nanostrip with perpendicular magnetic anisotropy by means of micromagnetic simulation. SW carries spin angular momentum and can interact with DWs via Spin Transfer Torque (STT). Propagating SW can drive a DW motion depending on the in-plane tilt angle φ of the wall magnetization. We calculate the instantaneous velocity of DWs as a function of φwith different SW frequency f. We find that the DW motion under propagating SW depends not only on the frequencies f, but also on the in-plane tilt angle φ. The nanostrip considered is 50 nm wide and 4000 nm long. A DW at the center is subjected to a SW source 500 nm apart on the left with amplitude in the transverse direction and varying frequency f. The motions of the DW induced by the SW are accompanied by in-plane rotation of magnetization of DW. Once rotated by 90 degrees, the DW shows a backward motion towards the SW source. The oscillatory amplitude and frequency of the DW motion is analyzed. A phase diagram will be presented. This study provides new perspectives for the control and manipulation of DW in a nanostrip. Financial supports by Academia Sinica and National Science Council are acknowledged

Data analysis of gravitational-wave signals from spinning neutron stars. III. Detection statistics and computational requirements

NASA Astrophysics Data System (ADS)

Jaranowski, Piotr; Królak, Andrzej

2000-03-01

We develop the analytic and numerical tools for data analysis of the continuous gravitational-wave signals from spinning neutron stars for ground-based laser interferometric detectors. The statistical data analysis method that we investigate is maximum likelihood detection which for the case of Gaussian noise reduces to matched filtering. We study in detail the statistical properties of the optimum functional that needs to be calculated in order to detect the gravitational-wave signal and estimate its parameters. We find it particularly useful to divide the parameter space into elementary cells such that the values of the optimal functional are statistically independent in different cells. We derive formulas for false alarm and detection probabilities both for the optimal and the suboptimal filters. We assess the computational requirements needed to do the signal search. We compare a number of criteria to build sufficiently accurate templates for our data analysis scheme. We verify the validity of our concepts and formulas by means of the Monte Carlo simulations. We present algorithms by which one can estimate the parameters of the continuous signals accurately. We find, confirming earlier work of other authors, that given a 100 Gflops computational power an all-sky search for observation time of 7 days and directed search for observation time of 120 days are possible whereas an all-sky search for 120 days of observation time is computationally prohibitive.

Abnormal Elasticity of Single-Crystal Magnesiosiderite across the Spin Transition in Earth's Lower Mantle

NASA Astrophysics Data System (ADS)

Fu, S.; Yang, J.; Lin, J. F.

2016-12-01

Carbon can be transported into deep Earth's interior via subduction of carbonated oceanic crust, hosted as Mg-Fe bearing carbonates. The existence of stable carbonate can significantly affect our understanding on geochemical and geophysical properties of the planet. Early studies have shown that iron spin-pairing transition could occur in the iron-enriched carbonates, generally called magnesiosiderite, under lower mantle conditions. The pressure-induced spin state change is accompanied by a sudden volume collaps. However, the effects of the spin-pairing transition on single-crystal elasticity of magnesiosiderite under high pressure conditions are still unclear. Understanding the elasticity of single-crystal magnesiosiderite at relevant lower mantle conditions plays an important role in better understanding the seismic signatures in the carbon-enriched region, and to constrain carbon storage and recycling in the mantle. In order to solve all individual elastic constants (C11, C22, C33, C44, C55, C66, C12, C23, and C13) of magnesiosiderite at high pressures via Christoffel's equations, we employed Brillouin Light Scattering (BLS) to measure shear wave (Vs) and compressional wave velocities (Vp) as a function of the azimuthal angle under lower mantle pressures, accompanied by Impulsive Stimulate Light Scattering (ISS) to measure the Vp when pressures are too high to measure it by BLS. A general thermoelastic modelling was developed to fit the elastic softening within the spin transition. We will further discuss the effects of pressures, as well as iron spin states, on the single-crystal elasticity and seismic parameters (Vp and Vs anisotropy AVp, AVs, etc) at lower mantle conditions. These results could provide clues in explaining regional seismic heterogeneities in deep mantle.

Searches for Gravitational Waves from Known Pulsars with Science Run 5 LIGO Data

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Acernese, F.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Alshourbagy, M.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Aoudia, S.; Arain, M. A.; Araya, M.; Armandula, H.; Armor, P.; Arun, K. G.; Aso, Y.; Aston, S.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, C.; Barker, D.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauer, Th. S.; Behnke, B.; Beker, M.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bigotta, S.; Bilenko, I. A.; Billingsley, G.; Birindelli, S.; Biswas, R.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Boccara, C.; Bodiya, T. P.; Bogue, L.; Bondu, F.; Bonelli, L.; Bork, R.; Boschi, V.; Bose, S.; Bosi, L.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Van Den Broeck, C.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Brunet, G.; Budzyński, R.; Bulik, T.; Bullington, A.; Bulten, H. J.; Buonanno, A.; Burmeister, O.; Buskulic, D.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campagna, E.; Cannizzo, J.; Cannon, K. C.; Canuel, B.; Cao, J.; Carbognani, F.; Cardenas, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cokelaer, T.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Corda, C.; Cornish, N.; Corsi, A.; Coulon, J.-P.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dari, A.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; De Rosa, R.; DeBra, D.; Degallaix, J.; del Prete, M.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drago, M.; Drever, R. W. P.; Dueck, J.; Duke, I.; Dumas, J.-C.; Dwyer, J. G.; Echols, C.; Edgar, M.; Effler, A.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmann, H.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Franzen, A.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Granata, M.; Granata, V.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grimaldi, F.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Guidi, G.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Hoyland, D.; Huet, D.; Hughey, B.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ito, M.; Ivanov, A.; Jaranowski, P.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Sancho de la Jordana, L.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Krishnan, B.; Królak, A.; Kumar, R.; Kwee, P.; La Penna, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, H.; Lei, M.; Leindecker, N.; Leonor, I.; Leroy, N.; Letendre, N.; Li, C.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Longo, M.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Lubiński, M.; Lucianetti, A.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mackowski, J.-M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McIntyre, G.; McKechan, D. J. A.; McKenzie, K.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Menzinger, F.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Michel, C.; Milano, L.; Miller, J.; Minelli, J.; Minenkov, Y.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Morioka, T.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; MowLowry, C.; Mueller, G.; Muhammad, D.; zur Mühlen, H.; Mukherjee, S.; Mukhopadhyay, H.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Myers, E.; Myers, J.; Nash, T.; Nelson, J.; Neri, I.; Newton, G.; Nishizawa, A.; Nocera, F.; Numata, K.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pagliaroli, G.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parameshwaraiah, V.; Pardi, S.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pedraza, M.; Penn, S.; Perreca, A.; Persichetti, G.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Principe, M.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabaste, O.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rainer, N.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Rivera, B.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Russell, P.; Ryan, K.; Sakata, S.; Salemi, F.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Saraf, S.; Sarin, P.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Savov, P.; Scanlan, M.; Schilling, R.; Schnabel, R.; Schofield, R.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sinha, S.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; van der Sluys, M. V.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Stein, A.; Stein, L. C.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, K.-X.; Sung, M.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Terenzi, R.; Thacker, J.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torres, C.; Torrie, C.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Trummer, J.; Ugolini, D.; Ulmen, J.; Urbanek, K.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van der Putten, S.; Vass, S.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; van Veggel, A. A.; Veitch, J.; Veitch, P.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, R. L.; Was, M.; Weidner, A.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Wilmut, I.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Yvert, M.; Zanolin, M.; Zhang, J.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; Bégin, S.; Corongiu, A.; D'Amico, N.; Freire, P. C. C.; Hessels, J. W. T.; Hobbs, G. B.; Kramer, M.; Lyne, A. G.; Manchester, R. N.; Marshall, F. E.; Middleditch, J.; Possenti, A.; Ransom, S. M.; Stairs, I. H.; Stappers, B.; LIGO Scientific Collaboration; Virgo Collaboration

2010-04-01

We present a search for gravitational waves from 116 known millisecond and young pulsars using data from the fifth science run of the LIGO detectors. For this search, ephemerides overlapping the run period were obtained for all pulsars using radio and X-ray observations. We demonstrate an updated search method that allows for small uncertainties in the pulsar phase parameters to be included in the search. We report no signal detection from any of the targets and therefore interpret our results as upper limits on the gravitational wave signal strength. The most interesting limits are those for young pulsars. We present updated limits on gravitational radiation from the Crab pulsar, where the measured limit is now a factor of 7 below the spin-down limit. This limits the power radiated via gravitational waves to be less than ~2% of the available spin-down power. For the X-ray pulsar J0537 - 6910 we reach the spin-down limit under the assumption that any gravitational wave signal from it stays phase locked to the X-ray pulses over timing glitches, and for pulsars J1913+1011 and J1952+3252 we are only a factor of a few above the spin-down limit. Of the recycled millisecond pulsars, several of the measured upper limits are only about an order of magnitude above their spin-down limits. For these our best (lowest) upper limit on gravitational wave amplitude is 2.3 × 10-26 for J1603 - 7202 and our best (lowest) limit on the inferred pulsar ellipticity is 7.0 × 10-8 for J2124 - 3358.

Scattering of Dirac waves off Kerr black holes

NASA Astrophysics Data System (ADS)

Chakrabarti, Sandip K.; Mukhopadhyay, Banibrata

2000-10-01

Chandrasekhar separated the Dirac equation for spinning and massive particles in Kerr geometry into radial and angular parts. Here we solve the complete wave equation and find out how the Dirac wave scatters off Kerr black holes. The eigenfunctions, eigenvalues and reflection and transmission co-efficients are computed. We compare the solutions with several parameters to show how a spinning black hole recognizes the mass and energy of incoming waves. Very close to the horizon the solutions become independent of the particle parameters, indicating the universality of the behaviour.

Fermion superfluid with hybridized s- and p-wave pairings

NASA Astrophysics Data System (ADS)

Zhou, LiHong; Yi, Wei; Cui, XiaoLing

2017-12-01

Ever since the pioneering work of Bardeen, Cooper and Schrieffer in the 1950s, exploring novel pairing mechanisms for fermion superfluids has become one of the central tasks in modern physics. Here, we investigate a new type of fermion superfluid with hybridized s- and p-wave pairings in an ultracold spin-1/2 Fermi gas. Its occurrence is facilitated by the co-existence of comparable s- and p-wave interactions, which is realizable in a two-component 40K Fermi gas with close-by s- and p-wave Feshbach resonances. The hybridized superfluid state is stable over a considerable parameter region on the phase diagram, and can lead to intriguing patterns of spin densities and pairing fields in momentum space. In particular, it can induce a phase-locked p-wave pairing in the fermion species that has no p-wave interactions. The hybridized nature of this novel superfluid can also be confirmed by measuring the s- and p-wave contacts, which can be extracted from the high-momentum tail of the momentum distribution of each spin component. These results enrich our knowledge of pairing superfluidity in Fermi systems, and open the avenue for achieving novel fermion superfluids with multiple partial-wave scatterings in cold atomic gases.

Design of Transverse Spinning of Light with Globally Unique Handedness

NASA Astrophysics Data System (ADS)

Piao, Xianji; Yu, Sunkyu; Park, Namkyoo

2018-05-01

Access to the transverse spin of light has unlocked new regimes in topological photonics. To achieve the transverse spin from nonzero longitudinal fields, various platforms that derive transversely confined waves based on focusing, interference, or evanescent waves have been suggested. Nonetheless, because of the transverse confinement inherently accompanying sign reversal of the field derivative, the resulting transverse spin handedness of each field experiences spatial inversion, which leads to a mismatch between the intensities of the field and its spin component and hinders the global observation of the transverse spin. Here, we reveal a globally pure transverse spin of the electric field in which the field intensity signifies the spin distribution. Starting from the target spin mode for the inverse design of required spatial profiles of anisotropic permittivities, we show that the elliptic-hyperbolic transition around the epsilon-near-zero permittivity allows for the global conservation of transverse spin handedness of the electric field across the topological interface between anisotropic metamaterials. Extending to the non-Hermitian regime, we develop annihilated transverse spin modes to cover the entire Poincaré sphere of the meridional plane. This result realizes the complete optical analogy of three-dimensional quantum spin states.

Magnetic Fluctuations in Pair-Density-Wave Superconductors

NASA Astrophysics Data System (ADS)

Christensen, Morten H.; Jacobsen, Henrik; Maier, Thomas A.; Andersen, Brian M.

2016-04-01

Pair-density-wave superconductivity constitutes a novel electronic condensate proposed to be realized in certain unconventional superconductors. Establishing its potential existence is important for our fundamental understanding of superconductivity in correlated materials. Here we compute the dynamical magnetic susceptibility in the presence of a pair-density-wave ordered state and study its fingerprints on the spin-wave spectrum including the neutron resonance. In contrast to the standard case of d -wave superconductivity, we show that the pair-density-wave phase exhibits neither a spin gap nor a magnetic resonance peak, in agreement with a recent neutron scattering experiment on underdoped La1.905 Ba0.095 CuO4 [Z. Xu et al., Phys. Rev. Lett. 113, 177002 (2014)].

Solution of Dirac equation for Eckart potential and trigonometric Manning Rosen potential using asymptotic iteration method

NASA Astrophysics Data System (ADS)

Resita Arum, Sari; A, Suparmi; C, Cari

2016-01-01

The Dirac equation for Eckart potential and trigonometric Manning Rosen potential with exact spin symmetry is obtained using an asymptotic iteration method. The combination of the two potentials is substituted into the Dirac equation, then the variables are separated into radial and angular parts. The Dirac equation is solved by using an asymptotic iteration method that can reduce the second order differential equation into a differential equation with substitution variables of hypergeometry type. The relativistic energy is calculated using Matlab 2011. This study is limited to the case of spin symmetry. With the asymptotic iteration method, the energy spectra of the relativistic equations and equations of orbital quantum number l can be obtained, where both are interrelated between quantum numbers. The energy spectrum is also numerically solved using the Matlab software, where the increase in the radial quantum number nr causes the energy to decrease. The radial part and the angular part of the wave function are defined as hypergeometry functions and visualized with Matlab 2011. The results show that the disturbance of a combination of the Eckart potential and trigonometric Manning Rosen potential can change the radial part and the angular part of the wave function. Project supported by the Higher Education Project (Grant No. 698/UN27.11/PN/2015).

Classical aspects of higher spin topologically massive gravity

NASA Astrophysics Data System (ADS)

Chen, Bin; Long, Jiang; Zhang, Jian-Dong

2012-10-01

We study the classical solutions of three-dimensional topologically massive gravity (TMG) and its higher spin generalization, in the first-order formulation. The action of higher spin TMG has been proposed by Chen and Long (2011 J. High Energy Phys. JHEP12(2011)114) to be of a Chern-Simons-like form. The equations of motion are more complicated than the ones in pure higher spin AdS3 gravity, but are still tractable. As all the solutions in higher spin gravity are automatically the solutions of higher spin TMG, we focus on other solutions. We manage to find the AdS pp-wave solutions with higher spin hair and find that the non-vanishing higher spin fields may or may not modify the pp-wave geometry. In order to discuss the warped spacetime, we introduce the notion of a special Killing vector, which is defined to be the symmetry on the frame-like fields. We reproduce various warped spacetimes of TMG in our framework, with the help of special Killing vectors.

Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory

NASA Astrophysics Data System (ADS)

Gündoǧan, M.; Mazzera, M.; Ledingham, P. M.; Cristiani, M.; de Riedmatten, H.

2013-04-01

We report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.

Two-dimensional dispersion of magnetostatic volume spin waves

NASA Astrophysics Data System (ADS)

Buijnsters, Frank J.; van Tilburg, Lennert J. A.; Fasolino, Annalisa; Katsnelson, Mikhail I.

2018-06-01

Owing to the dipolar (magnetostatic) interaction, long-wavelength spin waves in in-plane magnetized films show an unusual dispersion behavior, which can be mathematically described by the model of and and refinements thereof. However, solving the two-dimensional dispersion requires the evaluation of a set of coupled transcendental equations and one has to rely on numerics. In this work, we present a systematic perturbative analysis of the spin wave model. An expansion in the in-plane wavevector allows us to obtain explicit closed-form expressions for the dispersion relation and mode profiles in various asymptotic regimes. Moreover, we derive a very accurate semi-analytical expression for the dispersion relation of the lowest-frequency mode that is straightforward to evaluate.

Spin-density wave state in simple hexagonal graphite

NASA Astrophysics Data System (ADS)

Mosoyan, K. S.; Rozhkov, A. V.; Sboychakov, A. O.; Rakhmanov, A. L.

2018-02-01

Simple hexagonal graphite, also known as AA graphite, is a metastable configuration of graphite. Using tight-binding approximation, it is easy to show that AA graphite is a metal with well-defined Fermi surface. The Fermi surface consists of two sheets, each shaped like a rugby ball. One sheet corresponds to electron states, another corresponds to hole states. The Fermi surface demonstrates good nesting: a suitable translation in the reciprocal space superposes one sheet onto another. In the presence of the electron-electron repulsion, a nested Fermi surface is unstable with respect to spin-density-wave ordering. This instability is studied using the mean-field theory at zero temperature, and the spin-density-wave order parameter is evaluated.

A scenario for magnonic spin-wave traps

PubMed Central

Busse, Frederik; Mansurova, Maria; Lenk, Benjamin; von der Ehe, Marvin; Münzenberg, Markus

2015-01-01

Spatially resolved measurements of the magnetization dynamics on a thin CoFeB film induced by an intense laser pump-pulse reveal that the frequencies of resulting spin-wave modes depend strongly on the distance to the pump center. This can be attributed to a laser generated temperature profile. We determine a shift of 0.5 GHz in the spin-wave frequency due to the spatial thermal profile induced by the femtosecond pump pulse that persists for up to one nanosecond. Similar experiments are presented for a magnonic crystal composed of a CoFeB-film based antidot lattice with a Damon Eshbach mode at the Brillouin zone boundary and its consequences are discussed. PMID:26279466

Entanglement of light-shift compensated atomic spin waves with telecom light.

PubMed

Dudin, Y O; Radnaev, A G; Zhao, R; Blumoff, J Z; Kennedy, T A B; Kuzmich, A

2010-12-31

Entanglement of a 795 nm light polarization qubit and an atomic Rb spin-wave qubit for a storage time of 0.1 s is observed by measuring the violation of Bell's inequality (S=2.65±0.12). Long qubit storage times are achieved by pinning the spin wave in a 1064 nm wavelength optical lattice, with a magic-valued magnetic field superposed to eliminate lattice-induced dephasing. Four-wave mixing in a cold Rb gas is employed to perform light qubit conversion between near infrared (795 nm) and telecom (1367 nm) wavelengths, and after propagation in a telecom fiber, to invert the conversion process. Observed Bell inequality violation (S=2.66±0.09), at 10 ms storage, confirms preservation of memory-light entanglement through the two stages of light qubit frequency conversion.

A direct method to transform between expansions in the configuration state function and Slater determinant bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsen, Jeppe, E-mail: jeppe@chem.au.dk

2014-07-21

A novel algorithm is introduced for the transformation of wave functions between the bases of Slater determinants (SD) and configuration state functions (CSF) in the genealogical coupling scheme. By modifying the expansion coefficients as each electron is spin-coupled, rather than performing a single many-electron transformation, the large transformation matrix that plagues previous approaches is avoided and the required number of operations is drastically reduced. As an example of the efficiency of the algorithm, the transformation for a configuration with 30 unpaired electrons and singlet spin is discussed. For this case, the 10 × 10{sup 6} coefficients in the CSF basismore » is obtained from the 150 × 10{sup 6} coefficients in the SD basis in 1 min, which should be compared with the seven years that the previously employed method is estimated to require.« less

Energy decomposition analysis of single bonds within Kohn-Sham density functional theory.

PubMed

Levine, Daniel S; Head-Gordon, Martin

2017-11-28

An energy decomposition analysis (EDA) for single chemical bonds is presented within the framework of Kohn-Sham density functional theory based on spin projection equations that are exact within wave function theory. Chemical bond energies can then be understood in terms of stabilization caused by spin-coupling augmented by dispersion, polarization, and charge transfer in competition with destabilizing Pauli repulsions. The EDA reveals distinguishing features of chemical bonds ranging across nonpolar, polar, ionic, and charge-shift bonds. The effect of electron correlation is assessed by comparison with Hartree-Fock results. Substituent effects are illustrated by comparing the C-C bond in ethane against that in bis(diamantane), and dispersion stabilization in the latter is quantified. Finally, three metal-metal bonds in experimentally characterized compounds are examined: a [Formula: see text]-[Formula: see text] dimer, the [Formula: see text]-[Formula: see text] bond in dizincocene, and the Mn-Mn bond in dimanganese decacarbonyl.

Coherence rephasing combined with spin-wave storage using chirped control pulses

NASA Astrophysics Data System (ADS)

Demeter, Gabor

2014-06-01

Photon-echo based optical quantum memory schemes often employ intermediate steps to transform optical coherences to spin coherences for longer storage times. We analyze a scheme that uses three identical chirped control pulses for coherence rephasing in an inhomogeneously broadened ensemble of three-level Λ systems. The pulses induce a cyclic permutation of the atomic populations in the adiabatic regime. Optical coherences created by a signal pulse are stored as spin coherences at an intermediate time interval, and are rephased for echo emission when the ensemble is returned to the initial state. Echo emission during a possible partial rephasing when the medium is inverted can be suppressed with an appropriate choice of control pulse wave vectors. We demonstrate that the scheme works in an optically dense ensemble, despite control pulse distortions during propagation. It integrates conveniently the spin-wave storage step into memory schemes based on a second rephasing of the atomic coherences.

Mutual influence between macrospin reversal order and spin-wave dynamics in isolated artificial spin-ice vertices

DOE PAGES

Montoncello, F.; Giovannini, L.; Bang, Wonbae; ...

2018-01-18

In this paper, we theoretically and experimentally investigate magnetization reversal and associated spin-wave dynamics of isolated threefold vertices that constitute a Kagome lattice. The three permalloy macrospins making up the vertex have an elliptical cross section and a uniform thickness. We study the dc magnetization curve and the frequency versus field curves (dispersions) of those spin-wave modes that produce the largest response. We also investigate each macrospin reversal from a dynamic perspective, by performing micromagnetic simulations of the reversal processes, and revealing their relationships to the soft-mode profile calculated at the equilibrium state immediately before reversal. The theoretical results aremore » compared with the measured magnetization curves and ferromagnetic resonance spectra. Finally, the agreement achieved suggests that a much deeper understanding of magnetization reversal and accompanying hysteresis can be achieved by combining theoretical calculations with static and dynamic magnetization experiments.« less

Mutual influence between macrospin reversal order and spin-wave dynamics in isolated artificial spin-ice vertices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montoncello, F.; Giovannini, L.; Bang, Wonbae

In this paper, we theoretically and experimentally investigate magnetization reversal and associated spin-wave dynamics of isolated threefold vertices that constitute a Kagome lattice. The three permalloy macrospins making up the vertex have an elliptical cross section and a uniform thickness. We study the dc magnetization curve and the frequency versus field curves (dispersions) of those spin-wave modes that produce the largest response. We also investigate each macrospin reversal from a dynamic perspective, by performing micromagnetic simulations of the reversal processes, and revealing their relationships to the soft-mode profile calculated at the equilibrium state immediately before reversal. The theoretical results aremore » compared with the measured magnetization curves and ferromagnetic resonance spectra. Finally, the agreement achieved suggests that a much deeper understanding of magnetization reversal and accompanying hysteresis can be achieved by combining theoretical calculations with static and dynamic magnetization experiments.« less

Soliton solution for the spin current in a ferromagnetic nanowire.

PubMed

Li, Zai-Dong; Li, Qiu-Yan; Li, Lu; Liu, W M

2007-08-01

We investigate the interaction of a periodic solution and a one-soliton solution for the spin-polarized current in a uniaxial ferromagnetic nanowire. The amplitude and wave number of the periodic solution for the spin current give different contributions to the width, velocity, and amplitude of the soliton. Moreover, we found that the soliton can be trapped only in space with proper conditions. Finally, we analyze the modulation instability and discuss dark solitary wave propagation for a spin current on the background of a periodic solution. In some special cases, the solution can be expressed as the linear combination of the periodic and soliton solutions.

Generalized extended Navier-Stokes theory: multiscale spin relaxation in molecular fluids.

PubMed

Hansen, J S

2013-09-01

This paper studies the relaxation of the molecular spin angular velocity in the framework of generalized extended Navier-Stokes theory. Using molecular dynamics simulations, it is shown that for uncharged diatomic molecules the relaxation time decreases with increasing molecular moment of inertia per unit mass. In the regime of large moment of inertia the fast relaxation is wave-vector independent and dominated by the coupling between spin and the fluid streaming velocity, whereas for small inertia the relaxation is slow and spin diffusion plays a significant role. The fast wave-vector-independent relaxation is also observed for highly packed systems. The transverse and longitudinal spin modes have, to a good approximation, identical relaxation, indicating that the longitudinal and transverse spin viscosities have same value. The relaxation is also shown to be isomorphic invariant. Finally, the effect of the coupling in the zero frequency and wave-vector limit is quantified by a characteristic length scale; if the system dimension is comparable to this length the coupling must be included into the fluid dynamical description. It is found that the length scale is independent of moment of inertia but dependent on the state point.

Angle-dependent spin-wave resonance spectroscopy of (Ga,Mn)As films

NASA Astrophysics Data System (ADS)

Dreher, L.; Bihler, C.; Peiner, E.; Waag, A.; Schoch, W.; Limmer, W.; Goennenwein, S. T. B.; Brandt, M. S.

2013-06-01

A modeling approach for standing spin-wave resonances based on a finite-difference formulation of the Landau-Lifshitz-Gilbert equation is presented. In contrast to a previous study [C. Bihler , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.79.045205 79, 045205 (2009)], this formalism accounts for elliptical magnetization precession and magnetic properties arbitrarily varying across the layer thickness, including the magnetic anisotropy parameters, the exchange stiffness, the Gilbert damping, and the saturation magnetization. To demonstrate the usefulness of our modeling approach, we experimentally study a set of (Ga,Mn)As samples grown by low-temperature molecular-beam epitaxy by means of angle-dependent standing spin-wave resonance spectroscopy and electrochemical capacitance-voltage measurements. By applying our modeling approach, the angle dependence of the spin-wave resonance data can be reproduced in a simulation with one set of simulation parameters for all external field orientations. We find that the approximately linear gradient in the out-of-plane magnetic anisotropy is related to a linear gradient in the hole concentrations of the samples.

Solid State Spin-Wave Quantum Memory for Time-Bin Qubits.

PubMed

Gündoğan, Mustafa; Ledingham, Patrick M; Kutluer, Kutlu; Mazzera, Margherita; de Riedmatten, Hugues

2015-06-12

We demonstrate the first solid-state spin-wave optical quantum memory with on-demand read-out. Using the full atomic frequency comb scheme in a Pr(3+):Y2SiO5 crystal, we store weak coherent pulses at the single-photon level with a signal-to-noise ratio >10. Narrow-band spectral filtering based on spectral hole burning in a second Pr(3+):Y2SiO5 crystal is used to filter out the excess noise created by control pulses to reach an unconditional noise level of (2.0±0.3)×10(-3) photons per pulse. We also report spin-wave storage of photonic time-bin qubits with conditional fidelities higher than achievable by a measure and prepare strategy, demonstrating that the spin-wave memory operates in the quantum regime. This makes our device the first demonstration of a quantum memory for time-bin qubits, with on-demand read-out of the stored quantum information. These results represent an important step for the use of solid-state quantum memories in scalable quantum networks.

Spin configurations on a decorated square lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mert, Gülistan; Mert, H. Şevki

Spin configurations on a decorated square lattice are investigated using Bertaut’s microscopic method. We have obtained collinear and non-collinear (canted) modes for the given wave vectors in the ground state. We have found ferromagnetic and antiferromagnetic commensurate spin configurations. We have found canted incommensurate spin configurations.

Multistage electronic nematic transitions in cuprate superconductors: A functional-renormalization-group analysis

NASA Astrophysics Data System (ADS)

Tsuchiizu, Masahisa; Kawaguchi, Kouki; Yamakawa, Youichi; Kontani, Hiroshi

2018-04-01

Recently, complex rotational symmetry-breaking phenomena have been discovered experimentally in cuprate superconductors. To find the realized order parameters, we study various unconventional charge susceptibilities in an unbiased way by applying the functional-renormalization-group method to the d -p Hubbard model. Without assuming the wave vector of the order parameter, we reveal that the most dominant instability is the uniform (q =0 ) charge modulation on the px and py orbitals, which possesses d symmetry. This uniform nematic order triggers another nematic p -orbital density wave along the axial (Cu-Cu) direction at Qa≈(π /2 ,0 ) . It is predicted that uniform nematic order is driven by the spin fluctuations in the pseudogap region, and another nematic density-wave order at q =Qa is triggered by the uniform order. The predicted multistage nematic transitions are caused by Aslamazov-Larkin-type fluctuation-exchange processes.

Physics of Electronic Materials

NASA Astrophysics Data System (ADS)

Rammer, Jørgen

2017-03-01

1. Quantum mechanics; 2. Quantum tunneling; 3. Standard metal model; 4. Standard conductor model; 5. Electric circuit theory; 6. Quantum wells; 7. Particle in a periodic potential; 8. Bloch currents; 9. Crystalline solids; 10. Semiconductor doping; 11. Transistors; 12. Heterostructures; 13. Mesoscopic physics; 14. Arithmetic, logic and machines; Appendix A. Principles of quantum mechanics; Appendix B. Dirac's delta function; Appendix C. Fourier analysis; Appendix D. Classical mechanics; Appendix E. Wave function properties; Appendix F. Transfer matrix properties; Appendix G. Momentum; Appendix H. Confined particles; Appendix I. Spin and quantum statistics; Appendix J. Statistical mechanics; Appendix K. The Fermi-Dirac distribution; Appendix L. Thermal current fluctuations; Appendix M. Gaussian wave packets; Appendix N. Wave packet dynamics; Appendix O. Screening by symmetry method; Appendix P. Commutation and common eigenfunctions; Appendix Q. Interband coupling; Appendix R. Common crystal structures; Appendix S. Effective mass approximation; Appendix T. Integral doubling formula; Bibliography; Index.

Ab initio study of the RbSr electronic structure: potential energy curves, transition dipole moments, and permanent electric dipole moments.

PubMed

Pototschnig, Johann V; Krois, Günter; Lackner, Florian; Ernst, Wolfgang E

2014-12-21

Excited states and the ground state of the diatomic molecule RbSr were calculated by post Hartree-Fock molecular orbital theory up to 22 000 cm(-1). We applied a multireference configuration interaction calculation based on multiconfigurational self-consistent field wave functions. Both methods made use of effective core potentials and core polarization potentials. Potential energy curves, transition dipole moments, and permanent electric dipole moments were determined for RbSr and could be compared with other recent calculations. We found a good agreement with experimental spectra, which have been obtained recently by helium nanodroplet isolation spectroscopy. For the lowest two asymptotes (Rb (5s (2)S) + Sr (5s4d (3)P°) and Rb (5p (2)P°) + Sr (5s(2) (1)S)), which exhibit a significant spin-orbit coupling, we included relativistic effects by two approaches, one applying the Breit-Pauli Hamiltonian to the multireference configuration interaction wave functions, the other combining a spin-orbit Hamiltonian and multireference configuration interaction potential energy curves. Using the results for the relativistic potential energy curves that correspond to the Rb (5s (2)S) + Sr (5s4d (3)P°) asymptote, we have simulated dispersed fluorescence spectra as they were recently measured in our lab. The comparison with experimental data allows to benchmark both methods and demonstrate that spin-orbit coupling has to be included for the lowest states of RbSr.

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva, A.; Anderson, S. B.; Anderson, W. G.; Angelova, S. V.; Antier, S.; Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Atallah, D. V.; Aufmuth, P.; Aulbert, C.; AultONeal, K.; Austin, C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barkett, K.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bawaj, M.; Bayley, J. C.; Bazzan, M.; Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Bero, J. J.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Biscoveanu, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.; Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonilla, E.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bossie, K.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.; Calloni, E.; Camp, J. B.; Canizares, P.; Cannon, K. C.; Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Carney, M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerdá-Durán, P.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chase, E.; Chassande-Mottin, E.; Chatterjee, D.; Cheeseboro, B. D.; Chen, H. Y.; Chen, X.; Chen, Y.; Cheng, H.-P.; Chia, H.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani, G.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.; Clark, J. A.; Clearwater, P.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P.-F.; Cohen, D.; Colla, A.; Collette, C. G.; Cominsky, L. R.; Constancio, M.; Conti, L.; Cooper, S. J.; Corban, P.; Corbitt, T. R.; Cordero-Carrión, I.; Corley, K. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Dálya, G.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davis, D.; Daw, E. J.; Day, B.; De, S.; DeBra, D.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Demos, N.; Denker, T.; Dent, T.; De Pietri, R.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; De Rossi, C.; DeSalvo, R.; de Varona, O.; Devenson, J.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Dreissigacker, C.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dupej, P.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Estevez, D.; Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fee, C.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finstad, D.; Fiori, I.; Fiorucci, D.; Fishbach, M.; Fisher, R. P.; Fitz-Axen, M.; Flaminio, R.; Fletcher, M.; Fong, H.; Font, J. A.; Forsyth, P. W. F.; Forsyth, S. S.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar, S. G.; Garcia-Quiros, C.; Garufi, F.; Gateley, B.; Gaudio, S.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.; Goncharov, B.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Gretarsson, E. M.; Groot, P.; Grote, H.; Grunewald, S.; Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Halim, O.; Hall, B. R.; Hall, E. D.; Hamilton, E. Z.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hannuksela, O. A.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hinderer, T.; Ho, W. C. G.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough, J.; Houston, E. A.; Howell, E. J.; Hreibi, A.; Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J.-M.; Isi, M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi, C. V.; Kalogera, V.; Kamai, B.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.; Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, K.; Kim, W.; Kim, W. S.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kinley-Hanlon, M.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Knowles, T. D.; Koch, P.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia, A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.; Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.; Linker, S. D.; Littenberg, T. B.; Liu, J.; Lo, R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lovelace, G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macas, R.; Macfoy, S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña Hernandez, I.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.; Markosyan, A. S.; Markowitz, A.; Maros, E.; Marquina, A.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Mason, K.; Massera, E.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matas, A.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McCuller, L.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McNeill, L.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Mejuto-Villa, E.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, B. B.; Miller, J.; Millhouse, M.; Milovich-Goff, M. C.; Minazzoli, O.; Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moffa, D.; Moggi, A.; Mogushi, K.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muñiz, E. A.; Muratore, M.; Murray, P. G.; Napier, K.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Neilson, J.; Nelemans, G.; Nelson, T. J. N.; Nery, M.; Neunzert, A.; Nevin, L.; Newport, J. M.; Newton, G.; Ng, K. K. Y.; Nguyen, T. T.; Nichols, D.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; North, C.; Nuttall, L. K.; Oberling, J.; O'Dea, G. D.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Okada, M. A.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ormiston, R.; Ortega, L. F.; O'Shaughnessy, R.; Ossokine, S.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pace, A. E.; Page, J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, Howard; Pan, Huang-Wei; Pang, B.; Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Parida, A.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patil, M.; Patricelli, B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pirello, M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell, J.; Prasad, J.; Pratt, J. W. W.; Pratten, G.; Predoi, V.; Prestegard, T.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rajbhandari, B.; Rakhmanov, M.; Ramirez, K. E.; Ramos-Buades, A.; Rapagnani, P.; Raymond, V.; Razzano, M.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Ren, W.; Reyes, S. D.; Ricci, F.; Ricker, P. M.; Rieger, S.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romel, C. L.; Romie, J. H.; Rosińska, D.; Ross, M. P.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Rutins, G.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sanchez, L. E.; Sanchis-Gual, N.; Sandberg, V.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Scheel, M.; Scheuer, J.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schulte, B. W.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.; Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shaner, M. B.; Shao, L.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, L. P.; Singh, A.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.; Somala, S.; Son, E. J.; Sonnenberg, J. A.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staats, K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stevenson, S. P.; Stone, R.; Stops, D. J.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Strunk, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Suresh, J.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Tait, S. C.; Talbot, C.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Tasson, J. D.; Taylor, J. A.; Taylor, R.; Tewari, S. V.; Theeg, T.; Thies, F.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.; Torres-Forné, A.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.; Tso, R.; Tsukada, L.; Tsuna, D.; Tuyenbayev, D.; Ueno, K.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walet, R.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, J. Z.; Wang, W. H.; Wang, Y. F.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wessel, E. K.; Weßels, P.; Westerweck, J.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Wilken, D.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Wofford, J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.; Wysocki, D. M.; Xiao, S.; Yamamoto, H.; Yancey, C. C.; Yang, L.; Yap, M. J.; Yazback, M.; Yu, Hang; Yu, Haocun; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zelenova, T.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.-H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2017-12-01

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO's first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far.

Spin-electron acoustic soliton and exchange interaction in separate spin evolution quantum plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru

Separate spin evolution quantum hydrodynamics is generalized to include the Coulomb exchange interaction, which is considered as interaction between the spin-down electrons being in quantum states occupied by one electron. The generalized model is applied to study the non-linear spin-electron acoustic waves. Existence of the spin-electron acoustic soliton is demonstrated. Contributions of concentration, spin polarization, and exchange interaction to the properties of the spin electron acoustic soliton are studied.

Dynamical structure factor of the J1-J2 Heisenberg model in one dimension: The variational Monte Carlo approach

NASA Astrophysics Data System (ADS)

Ferrari, Francesco; Parola, Alberto; Sorella, Sandro; Becca, Federico

2018-06-01

The dynamical spin structure factor is computed within a variational framework to study the one-dimensional J1-J2 Heisenberg model. Starting from Gutzwiller-projected fermionic wave functions, the low-energy spectrum is constructed from two-spinon excitations. The direct comparison with Lanczos calculations on small clusters demonstrates the excellent description of both gapless and gapped (dimerized) phases, including incommensurate structures for J2/J1>0.5 . Calculations on large clusters show how the intensity evolves when increasing the frustrating ratio and give an unprecedented accurate characterization of the dynamical properties of (nonintegrable) frustrated spin models.

Transmittance and Tunneling Current through a Trapezoidal Barrier under Spin Polarization Consideration

NASA Astrophysics Data System (ADS)

Noor, F. A.; Nabila, E.; Mardianti, H.; Ariani, T. I.; Khairurrijal

2018-04-01

The transmittance and tunneling current in heterostructures under spin polarization consideration were studied by employing a zinc-blended structure for the heterostructures. An electron tunnels through a potential barrier by applying a bias voltage to the barrier, which is called the trapezoidal potential barrier. In order to study the transmittance, an Airy wave function approach was employed to find the transmittance. The obtained transmittance was then utilized to compute the tunneling current by using a Gauss quadrature method. It was shown that the transmittances were asymmetric with the incident angle of the electron. It was also shown that the tunneling currents increased as the bias voltage increased.

Field-induced spin density wave and spiral phases in a layered antiferromagnet

DOE PAGES

Stone, Matthew B.; Lumsden, Mark D.; Garlea, Vasile O.; ...

2015-07-28

Here we determine the low-field ordered magnetic phases of the S=1 dimerized antiferromagnet Ba 3Mn 2O 8 using single crystal neutron diffraction. We find that for magnetic fields between μ 0H=8.80 T and 10.56 T applied along themore » $$1\\bar{1}0$$ direction the system exhibits spin density wave order with incommensurate wave vectors of type (η,η,ε). For μ 0H > 10.56 T, the magnetic order changes to a spiral phase with incommensurate wave vectors only along the [hh0] direction. For both field induced ordered phases, the magnetic moments are lying in the plane perpendicular to the field direction. Finally, the nature of these two transitions is fundamentally different: the low-field transition is a second order transition to a spin-density wave ground state, while the one at higher field, toward the spiral phase, is of first order.« less

Novel Feshbach resonances in a ^40K spin-mixture

NASA Astrophysics Data System (ADS)

Walraven, J. T. M.; Ludewig, A.; Tiecke, T. G.

2010-03-01

We present experimental results on novel s-wave Feshbach resonances in ^40K spin-mixtures. Using an extended version of the Asymptotic Bound-state Model (ABM) [1] we predict Feshbach resonances with more promising characteristics than the commonly used resonances in the (|F,mF>) |9/2,-9/2>+|9/2,-7/2> and |9/2,-9/2>+|9/2,-5/2> spin mixtures. We report on an s-wave resonance in the |9/2,-5/2>+|9/2,-3/2> mixture. We have experimentally observed the corresponding loss-feature at B0˜178 G with a width of ˜10G. This resonance is promising due to its large predicted width and the absence of an overlapping p-wave resonance. We present our recent results on measurements of the resonance width and the stability of the system around this and other observed s-wave and p-wave resonances. [4pt] [1] T.G. Tiecke, et al., Phys. Rev. Lett. 104, 053202 (2010).

Multigap superconductivity in the charge density wave superconductor LaPt2Si2

NASA Astrophysics Data System (ADS)

Das, Debarchan; Gupta, Ritu; Bhattacharyya, A.; Biswas, P. K.; Adroja, D. T.; Hossain, Z.

2018-05-01

The superconducting gap structure of a charge density wave (CDW) superconductor LaPt2Si2 (Tc=1.6 K) having a quasi-two-dimensional crystal structure has been investigated using muon spin rotation/relaxation (μ SR ) measurements in transverse field (TF), zero field (ZF), and longitudinal field (LF) geometries. Rigorous analysis of TF-μ SR spectra in the superconducting state corroborates that the temperature dependence of the effective penetration depth, λL, derived from muon spin depolarization, fits to a two gap s wave model (i.e., s +s wave) suggesting that the Fermi surface contains two gaps of different magnitude rather than an isotropic gap expected for a conventional s wave superconductor. On the other hand, ZF μ SR data do not show any significant change in muon spin relaxation rate above and below the superconducting transition temperature indicating the fact that time-reversal symmetry is preserved in the superconducting state of this material.

Magnetohydrodynamic waves with relativistic electrons and positrons in degenerate spin-1/2 astrophysical plasmas

NASA Astrophysics Data System (ADS)

Maroof, R.; Ali, S.; Mushtaq, A.; Qamar, A.

2015-11-01

Linear properties of high and low frequency waves are studied in an electron-positron-ion (e-p-i) dense plasma with spin and relativity effects. In a low frequency regime, the magnetohydrodynamic (MHD) waves, namely, the magnetoacoustic and Alfven waves are presented in a magnetized plasma, in which the inertial ions are taken as spinless and non-degenerate, whereas the electrons and positrons are treated quantum mechanically due to their smaller mass. Quantum corrections associated with the spin magnetization and density correlations for electrons and positrons are re-considered and a generalized dispersion relation for the low frequency MHD waves is derived to account for relativistic degeneracy effects. On the basis of angles of propagation, the dispersion relations of different modes are discussed analytically in a degenerate relativistic plasma. Numerical results reveal that electron and positron relativistic degeneracy effects significantly modify the dispersive properties of MHD waves. Our present analysis should be useful for understanding the collective interactions in dense astrophysical compact objects, like, the white dwarfs and in atmosphere of neutron stars.

All optical detection of picosecond spin-wave dynamics in 2D annular antidot lattice

NASA Astrophysics Data System (ADS)

Porwal, Nikita; Mondal, Sucheta; Choudhury, Samiran; De, Anulekha; Sinha, Jaivardhan; Barman, Anjan; Datta, Prasanta Kumar

2018-02-01

Novel magnetic structures with precisely controlled dimensions and shapes at the nanoscale have potential applications in spin logic, spintronics and other spin-based communication devices. We report the fabrication of 2D bi-structure magnonic crystal in the form of embedded nanodots in a periodic Ni80Fe20 antidot lattice structure (annular antidot) by focused ion-beam lithography. The spin-wave spectra of the annular antidot sample, studied for the first time by a time-resolved magneto-optic Kerr effect microscopy show a remarkable variation with bias field, which is important for the above device applications. The optically induced spin-wave spectra show multiple modes in the frequency range 14.7 GHz-3.5 GHz due to collective interactions between the dots and antidots as well as the annular elements within the whole array. Numerical simulations qualitatively reproduce the experimental results, and simulated mode profiles reveal the spatial distribution of the spin-wave modes and internal magnetic fields responsible for these observations. It is observed that the internal field strength increases by about 200 Oe inside each dot embedded within the hole of annular antidot lattice as compared to pure antidot lattice and pure dot lattice. The stray field for the annular antidot lattice is found to be significant (0.8 kOe) as opposed to the negligible values of the same for the pure dot lattice and pure antidot lattice. Our findings open up new possibilities for development of novel artificial crystals.

Some Fundamental Issues in Ground-State Density Functional Theory: A Guide for the Perplexed.

PubMed

Perdew, John P; Ruzsinszky, Adrienn; Constantin, Lucian A; Sun, Jianwei; Csonka, Gábor I

2009-04-14

Some fundamental issues in ground-state density functional theory are discussed without equations: (1) The standard Hohenberg-Kohn and Kohn-Sham theorems were proven for a Hamiltonian that is not quite exact for real atoms, molecules, and solids. (2) The density functional for the exchange-correlation energy, which must be approximated, arises from the tendency of electrons to avoid one another as they move through the electron density. (3) In the absence of a magnetic field, either spin densities or total electron density can be used, although the former choice is better for approximations. (4) "Spin contamination" of the determinant of Kohn-Sham orbitals for an open-shell system is not wrong but right. (5) Only to the extent that symmetries of the interacting wave function are reflected in the spin densities should those symmetries be respected by the Kohn-Sham noninteracting or determinantal wave function. Functionals below the highest level of approximations should however sometimes break even those symmetries, for good physical reasons. (6) Simple and commonly used semilocal (lower-level) approximations for the exchange-correlation energy as a functional of the density can be accurate for closed systems near equilibrium and yet fail for open systems of fluctuating electron number. (7) The exact Kohn-Sham noninteracting state need not be a single determinant, but common approximations can fail when it is not. (8) Over an open system of fluctuating electron number, connected to another such system by stretched bonds, semilocal approximations make the exchange-correlation energy and hole-density sum rule too negative. (9) The gap in the exact Kohn-Sham band structure of a crystal underestimates the real fundamental gap but may approximate the first exciton energy in the large-gap limit. (10) Density functional theory is not really a mean-field theory, although it looks like one. The exact functional includes strong correlation, and semilocal approximations often overestimate the strength of static correlation through their semilocal exchange contributions. (11) Only under rare conditions can excited states arise directly from a ground-state theory.

Transfer-Matrix Method for Solving the Spin 1/2 Antiferromagnetic Heisenberg Chain

NASA Astrophysics Data System (ADS)

Garcia-Bach, M. A.; Klein, D. J.; Valenti, R.

Following the discovery of high Tc superconductivity in the copper oxides, there has been a great deal of interest in the RVB wave function proposed by Anderson [1]. As a warm-up exercise we have considered a valence-bond wave function for the one dimensional spin-1/2 Heisenberg chain. The main virtue of our work is to propose a new variational singlet wavefunction which is almost analytically tractable by a transfer-matrix technique. We have obtained the ground state energy for finite as well as infinite chains, in good agreement with exact results. Correlation functions, excited states, and the effects of other interactions (e.g., spin-Peierls) are also accessible within this scheme [2]. Since the ground state of the chain is known to be a singlet (Lieb & Mattis [3]), we write the appropriate wave function as a superposition of valence-bond singlets, |ψ > =∑ limits k C k | k>, where |k> is a spin configuration obtained by pairing all spins into singlet pairs, in a way which is common in valence-bond calculations of large molecules. As in that case, each configuration, |k>, can be represented by a Rümer diagram, with directed bonds connecting each pair of spins on the chain. The ck's are variational co-efficients, the form of which is determined as follows: Each singlet configuration (Rümer diagram) is divided into "zones", a "zone" corresponding to the region between two consecutive sites. Each zone is indexed by its distance from the end of the chain and by the number of bonds crossing it. Our procedure assigns a variational parameter, xij, to the jth zone, when crossed by i bonds. The resulting wavefunction for an N-site chain is written as |ψ > =∑ limits k ∏ M limits { i =1} ∏ { N -1}limits { j =1} X ij{ m ij (k)} | k> where mij(k) equals 1 when zone j is crossed by i bonds and zero otherwise. To make the calculation tractable we reduce the number of variational parameters by disallowing configurations with bonds connecting any two sites separated by more than 2M lattice points. (For simplicity, we have limited ourselves to M=3, but the scheme can be used for any M). With the simple ansatz, matrix elements can be calculated by a transfer-matrix method. To understand the transfer-matrix method note that since only local zone parameters appear in the description of each state |k>, matrix elements and overlaps, < k| bar S q bar S{ q +1} |k'> and , are completely specified by a small number of "local states" associated with each zone. Within a given zone a local state is defined by (i) the number of bonds crossing the zone and (ii), by whether the bonds originate from the initial (|k>) or final (|k'>) state. It is then easy to see that "local states" of consecutive zones are connected by a 15 × 15 transfer matrix (for the case M=3). Furthermore, the overlap matrix element can be written as a product of transfer-matrices associated with each zone of the chain. When calculating matrix elements of the Hamiltonian, an additional matrix, U, must be defined, to represent the particular zone involving the two spins connected by the Heisenberg interaction. The relevant details as well as the comparison with exact results will be given elsewhere. We are planning to ultimately apply this method to the two dimensional case, and hope to include the effects of holes.

Spin wave based parallel logic operations for binary data coded with domain walls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urazuka, Y.; Oyabu, S.; Chen, H.

2014-05-07

We numerically investigate the feasibility of spin wave (SW) based parallel logic operations, where the phase of SW packet (SWP) is exploited as a state variable and the phase shift caused by the interaction with domain wall (DW) is utilized as a logic inversion functionality. A designed functional element consists of parallel ferromagnetic nanowires (6 nm-thick, 36 nm-width, 5120 nm-length, and 200 nm separation) with the perpendicular magnetization and sub-μm scale overlaid conductors. The logic outputs for binary data, coded with the existence (“1”) or absence (“0”) of the DW, are inductively read out from interferometric aspect of the superposed SWPs, one of themmore » propagating through the stored data area. A practical exclusive-or operation, based on 2π periodicity in the phase logic, is demonstrated for the individual nanowire with an order of different output voltage V{sub out}, depending on the logic output for the stored data. The inductive output from the two nanowires exhibits well defined three different signal levels, corresponding to the information distance (Hamming distance) between 2-bit data stored in the multiple nanowires.« less

Spin-orbital fluctuations in the paramagnetic Mott insulator (V1-xCrx)2O3

NASA Astrophysics Data System (ADS)

Leiner, Jonathan; Stone, Matthew; Lumsden, Mark; Bao, Wei; Broholm, Collin

2015-03-01

The phase diagram of rhombohedral V2O3 features several distinct strongly correlated phases as a function of doping, pressure and temperature. When doped with chromium for 180 K

Control of circular polarization of electroluminescence in spin light-emitting diodes based on InGaAs/GaAs/δ〈Mn〉 heterostructures

NASA Astrophysics Data System (ADS)

Malysheva, E. I.; Dorokhin, M. V.; Demina, P. B.; Zdoroveyshchev, A. V.; Rykov, A. V.; Ved', M. V.; Danilov, Yu. A.

2017-11-01

Circularly polarized luminescence of light-emitting InGaAs/GaAs structures with a delta-doped Mn layer in a GaAs barrier was studied. The structural parameters were varied by different ways, among them are homogeneous and delta-doping with acceptor impurity, and removal of donor doping from the technological process. As it was found, the magnitude and polarity of the degree of circular polarization of luminescence strongly depend on the technological mode chosen. Simultaneous modeling of wave functions of structures highlights a good agreement between the parameters of circularly polarized luminescence and spatial distribution of wave functions of heavy holes relative to the Mn delta-layer.

Solving the quantum many-body problem with artificial neural networks

NASA Astrophysics Data System (ADS)

Carleo, Giuseppe; Troyer, Matthias

2017-02-01

The challenge posed by the many-body problem in quantum physics originates from the difficulty of describing the nontrivial correlations encoded in the exponential complexity of the many-body wave function. Here we demonstrate that systematic machine learning of the wave function can reduce this complexity to a tractable computational form for some notable cases of physical interest. We introduce a variational representation of quantum states based on artificial neural networks with a variable number of hidden neurons. A reinforcement-learning scheme we demonstrate is capable of both finding the ground state and describing the unitary time evolution of complex interacting quantum systems. Our approach achieves high accuracy in describing prototypical interacting spins models in one and two dimensions.

Modeling rapidly spinning, merging black holes with numerical relativity for the era of first gravitational-wave observations

NASA Astrophysics Data System (ADS)

Lovelace, Geoffrey; Simulating eXtreme Collaboration; LIGO Scientific Collaboration

2016-03-01

The Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO) began searching for gravitational waves in September 2015, with three times the sensitivity of the initial LIGO experiment. Merging black holes are among the most promising sources of gravitational waves for Advanced LIGO, but near the time of merger, the emitted waves can only be computed using numerical relativity. In this talk, I will present new numerical-relativity simulations of merging black holes, made using the Spectral Einstein Code [black-holes.org/SpEC.html], including cases with black-hole spins that are nearly as fast as possible. I will discuss how such simulations will be able to rapidly follow up gravitational-wave observations, improving our understanding of the waves' sources.

Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

NASA Astrophysics Data System (ADS)

Mukherjee, Arunava; Messenger, Chris; Riles, Keith

2018-02-01

The LIGO's discovery of binary black hole mergers has opened up a new era of transient gravitational wave astronomy. The potential detection of gravitational radiation from another class of astronomical objects, rapidly spinning nonaxisymmetric neutron stars, would constitute a new area of gravitational wave astronomy. Scorpius X-1 (Sco X-1) is one of the most promising sources of continuous gravitational radiation to be detected with present-generation ground-based gravitational wave detectors, such as Advanced LIGO and Advanced Virgo. As the sensitivity of these detectors improve in the coming years, so will power of the search algorithms being used to find gravitational wave signals. Those searches will still require integration over nearly year long observational spans to detect the incredibly weak signals from rotating neutron stars. For low mass X-ray binaries such as Sco X-1 this difficult task is compounded by neutron star "spin wandering" caused by stochastic accretion fluctuations. In this paper, we analyze X-ray data from the R X T E satellite to infer the fluctuating torque on the neutron star in Sco X-1. We then perform a large-scale simulation to quantify the statistical properties of spin-wandering effects on the gravitational wave signal frequency and phase evolution. We find that there are a broad range of expected maximum levels of frequency wandering corresponding to maximum drifts of between 0.3 - 50 μ Hz /sec over a year at 99% confidence. These results can be cast in terms of the maximum allowed length of a coherent signal model neglecting spin-wandering effects as ranging between 5-80 days. This study is designed to guide the development and evaluation of Sco X-1 search algorithms.

Self-oscillation of standing spin wave in ring resonator with proportional-integral-derivative control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, B.; Urazuka, Y.; Chen, H.

2014-05-07

We report on numerical analysis on self-oscillation of standing spin wave excited in a nanostructured active ring resonator, consists of a ferromagnetic nanowire with perpendicular anisotropy. The confined resonant modes are along the nanowire length. A positive feedback with proportional-integral-derivative gain control was adopted in the active ring. Stable excitation of the 1st order standing spin wave has been demonstrated with micromagnetic simulations, taking into account the thermal effect with a random field model. The stationary standing spin wave with a pre-determined set variable of precession amplitude was attained within 20 ns by optimizing the proportional-integral-derivative gain control parameters. The resultmore » indicates that a monochromatic oscillation frequency f{sub osc} is extracted from the initial thermal fluctuation state and selectively amplified with the positive feedback loop. The obtained f{sub osc} value of 5.22 GHz practically agrees with the theoretical prediction from dispersion relation of the magneto static forward volume wave. It was also confirmed that the f{sub osc} change due to the temperature rise can be compensated with an external perpendicular bias field H{sub b}. The observed quick compensation time with an order of nano second suggests the fast operation speed in the practical device application.« less

Photonic-magnonic crystals: Multifunctional periodic structures for magnonic and photonic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kłos, J. W., E-mail: klos@amu.edu.pl; Krawczyk, M.; Dadoenkova, Yu. S.

2014-05-07

We investigate the properties of a photonic-magnonic crystal, a complex multifunctional one-dimensional structure with magnonic and photonic band gaps in the GHz and PHz frequency ranges for spin waves and light, respectively. The system consists of periodically distributed dielectric magnetic slabs of yttrium iron garnet and nonmagnetic spacers with an internal structure of alternating TiO{sub 2} and SiO{sub 2} layers which form finite-size dielectric photonic crystals. We show that the spin-wave coupling between the magnetic layers, and thus the formation of the magnonic band structure, necessitates a nonzero in-plane component of the spin-wave wave vector. A more complex structure perceivedmore » by light is evidenced by the photonic miniband structure and the transmission spectra in which we have observed transmission peaks related to the repetition of the magnetic slabs in the frequency ranges corresponding to the photonic band gaps of the TiO{sub 2}/SiO{sub 2} stack. Moreover, we show that these modes split to very high sharp (a few THz wide) subpeaks in the transmittance spectra. The proposed novel multifunctional artificial crystals can have interesting applications and be used for creating common resonant cavities for spin waves and light to enhance the mutual influence between them.« less

Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

NASA Astrophysics Data System (ADS)

Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

2018-04-01

The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

Spin-density fluctuations and the fluctuation-dissipation theorem in 3 d ferromagnetic metals

DOE PAGES

Wysocki, Alex L.; Valmispild, V. N.; Kutepov, A.; ...

2017-11-15

Spatial and time scales of spin-density fluctuations (SDFs) were analyzed in 3d ferromagnets using ab initio linear-response calculations of complete wave-vector and energy dependence of the dynamic spin susceptibility tensor. We demonstrate that SDFs are spread continuously over the entire Brillouin zone and while the majority of them reside within the 3d bandwidth, a significant amount comes from much higher energies. A validity of the adiabatic approximation in spin dynamics is discussed. The SDF spectrum is shown to have two main constituents: a minor low-energy spin-wave contribution and a much larger high-energy component from more localized excitations. Furthermore, using themore » fluctuation-dissipation theorem, the on-site spin correlator and the related effective fluctuating moment were properly evaluated and their universal dependence on the 3d band population is further discussed.« less