Transverse-momentum-dependent quark distribution functions of spin-one targets: Formalism and covariant calculations

DOE PAGES

Ninomiya, Yu; Bentz, Wolfgang; Cloet, Ian C.

2017-10-24

In this paper, we present a covariant formulation and model calculations of the leading-twist time-reversal even transverse-momentum-dependent quark distribution functions (TMDs) for a spin-one target. Emphasis is placed on a description of these three-dimensional distribution functions which is independent of any constraints on the spin quantization axis. We apply our covariant spin description to all nine leading-twist time-reversal even ρ meson TMDs in the framework provided by the Nambu–Jona-Lasinio model, incorporating important aspects of quark confinement via the infrared cutoff in the proper-time regularization scheme. In particular, the behaviors of the three-dimensional TMDs in a tensor polarized spin-one hadron aremore » illustrated. Sum rules and positivity constraints are discussed in detail. Our results do not exhibit the familiar Gaussian behavior in the transverse momentum, and other results of interest include the finding that the tensor polarized TMDs—associated with spin-one hadrons—are very sensitive to quark orbital angular momentum, and that the TMDs associated with the quark operator γ +γ Tγ 5 would vanish were it not for dynamical chiral symmetry breaking. In addition, we find that 44% of the ρ meson's spin is carried by the orbital angular momentum of the quarks, and that the magnitude of the tensor polarized quark distribution function is about 30% of the unpolarized quark distribution. Finally, a qualitative comparison between our results for the tensor structure of a quark-antiquark bound state is made to existing experimental and theoretical results for the two-nucleon (deuteron) bound state.« less

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}.

3D Spin-Liquid State in an Organic Hyperkagome Lattice of Mott Dimers

NASA Astrophysics Data System (ADS)

Mizuno, Asato; Shuku, Yoshiaki; Matsushita, Michio M.; Tsuchiizu, Masahisa; Hara, Yuuki; Wada, Nobuo; Shimizu, Yasuhiro; Awaga, Kunio

2017-08-01

We report the first 3D spin liquid state of isotropic organic spins. Structural analysis, and magnetic and heat-capacity measurements were carried out for a chiral organic radical salt, (TBA) 1.5[(-)-NDI -Δ ] (TBA denotes tetrabutylammonium and NDI denotes naphthalene diimide), in which (-)-NDI -Δ forms a K4 structure due to its triangular molecular structure and an intermolecular π -π overlap between the NDI moieties. This lattice was identical to the hyperkagome lattice of S =1 /2 Mott dimers, and should exhibit 3D spin frustration. In fact, even though the high-temperature magnetic susceptibility followed the Curie-Weiss law with a negative Weiss constant of θ =-15 K , the low-temperature magnetic measurements revealed no long-range magnetic ordering down to 70 mK, and suggested the presence of a spin liquid state with a large residual paramagnetism χ0 of 8.5 ×10-6 emu g-1 at the absolute zero temperature. This was supported by the N 14 NMR measurements down to 0.38 K. Further, the low-temperature heat capacities cp down to 68 mK clearly indicated the presence of cp for the spin liquid state, which can be fitted to the power law of T0.62 in the wide temperature range 0.07-4.5 K.

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.

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves.

PubMed

Thurber, Kent R; Tycko, Robert

2014-05-14

We report solid state (13)C and (1)H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, (1)H and cross-polarized (13)C NMR signals from (15)N,(13)C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Optimally Squeezed Spin States

NASA Astrophysics Data System (ADS)

Rojo, Alberto

2004-03-01

We consider optimally spin-squeezed states that maximize the sensitivity of the Ramsey spectroscopy, and for which the signal to noise ratio scales as the number of particles N. Using the variational principle we prove that these states are eigensolutions of the Hamiltonian H(λ)=λ S_z^2-S_x, and that, for large N, the states become equivalent to the quadrature squeezed states of the harmonic oscillator. We present numerical results that illustrate the validity of the equivalence. We also present results of spin squeezing via atom-field interactions within the context of the Tavis-Cummings model. An ensemble of N two-level atoms interacts with a quantized cavity field. For all the atoms initially in their ground states, it is shown that spin squeezing of both the atoms and the field can be achieved provided the initial state of the cavity field has coherence between number states differing by 2. Most of the discussion is restricted to the case of a cavity field initially in a coherent state, but initial squeezed states for the field are also discussed. An analytic solution is found that is valid in the limit that the number of atoms is much greater than unity. References: A. G. Rojo, Phys. Rev A, 68, 013807 (2003); Claudiu Genes, P. R. Berman, and A. G. Rojo Phys. Rev. A 68, 043809 (2003).

Spin Rate Distribution of Small Asteroids Shaped by YORP Effect

NASA Astrophysics Data System (ADS)

Pravec, Petr

2008-09-01

We studied a distribution of spin rates of main belt/Mars crossing (MB/MC) asteroids with diameters 3-15 km using data obtained within the Photometric Survey of Asynchronous Binary Asteroids (Pravec et al. 2008). We found that the spin distribution of the small asteroids is uniform in the range from f = 1 to 9.5 d-1, and there is an excess of slow rotators with f < 1 d-1. The observed distribution appears to be controlled by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. The magnitude of the excess of slow rotators is related to the residence time of slowed down asteroids in the excess and the rate of spin rate change outside the excess. We estimated a median YORP spin rate change of 0.022 d-1/Myr for asteroids in our sample (i.e., a median time in which the spin rate changes by 1 d-1 is 45 Myr), thus the residence time of slowed down asteroids in the excess is 110 Myr. The spin rate distribution of near-Earth asteroids (NEAs) with sizes in the range 0.2-3 km ( 5-times smaller in median diameter than the MB/MC asteroids sample) shows a similar excess of slow rotators, but there is also a concentration of NEAs at fast spin rates with f = 9-10 d-1. The concentration at fast spin rates is correlated with a narrower distribution of spin rates of primaries of binary systems among NEAs; the difference may be due to the apparently more evolved population of binaries among MB/MC asteroids. Reference: Pravec, P., and 30 colleagues, 2008. Spin rate distribution of small asteroids. Icarus, in press. DOI: http://dx.doi.org/10.1016/j.icarus.2008.05.012

Constraining the noise-free distribution of halo spin parameters

NASA Astrophysics Data System (ADS)

Benson, Andrew J.

2017-11-01

Any measurement made using an N-body simulation is subject to noise due to the finite number of particles used to sample the dark matter distribution function, and the lack of structure below the simulation resolution. This noise can be particularly significant when attempting to measure intrinsically small quantities, such as halo spin. In this work, we develop a model to describe the effects of particle noise on halo spin parameters. This model is calibrated using N-body simulations in which the particle noise can be treated as a Poisson process on the underlying dark matter distribution function, and we demonstrate that this calibrated model reproduces measurements of halo spin parameter error distributions previously measured in N-body convergence studies. Utilizing this model, along with previous measurements of the distribution of halo spin parameters in N-body simulations, we place constraints on the noise-free distribution of halo spins. We find that the noise-free median spin is 3 per cent lower than that measured directly from the N-body simulation, corresponding to a shift of approximately 40 times the statistical uncertainty in this measurement arising purely from halo counting statistics. We also show that measurement of the spin of an individual halo to 10 per cent precision requires at least 4 × 104 particles in the halo - for haloes containing 200 particles, the fractional error on spins measured for individual haloes is of order unity. N-body simulations should be viewed as the results of a statistical experiment applied to a model of dark matter structure formation. When viewed in this way, it is clear that determination of any quantity from such a simulation should be made through forward modelling of the effects of particle noise.

Improving quantum state transfer efficiency and entanglement distribution in binary tree spin network through incomplete collapsing measurements

NASA Astrophysics Data System (ADS)

Behzadi, Naghi; Ahansaz, Bahram

2018-04-01

We propose a mechanism for quantum state transfer (QST) over a binary tree spin network on the basis of incomplete collapsing measurements. To this aim, we perform initially a weak measurement (WM) on the central qubit of the binary tree network where the state of our concern has been prepared on that qubit. After the time evolution of the whole system, a quantum measurement reversal (QMR) is performed on a chosen target qubit. By taking optimal value for the strength of QMR, it is shown that the QST quality from the sending qubit to any typical target qubit on the binary tree is considerably improved in terms of the WM strength. Also, we show that how high-quality entanglement distribution over the binary tree network is achievable by using this approach.

Spin-polarized surface resonances accompanying topological surface state formation

DOE PAGES

Jozwiak, Chris; Sobota, Jonathan A.; Gotlieb, Kenneth; ...

2016-10-14

Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi 2Se 3. By performing simultaneous spin, time, and angle-resolved photoemission spectroscopy, we map the spin-polarized unoccupied electronic structure and identify a surface resonance which is distinct from the topological surface state, yet shares a similar spin-orbital texture with opposite orientation. Its momentum dependence and spin texture imply an intimate connection with the topological surface state. Calculations show these two distinct states canmore » emerge from trivial Rashba-like states that change topology through the spin-orbit-induced band inversion. As a result, this work thus provides a compelling view of the coevolution of surface states through a topological phase transition, enabled by the unique capability of directly measuring the spin-polarized unoccupied band structure.« less

Spin-polarized surface resonances accompanying topological surface state formation

PubMed Central

Jozwiak, Chris; Sobota, Jonathan A.; Gotlieb, Kenneth; Kemper, Alexander F.; Rotundu, Costel R.; Birgeneau, Robert J.; Hussain, Zahid; Lee, Dung-Hai; Shen, Zhi-Xun; Lanzara, Alessandra

2016-01-01

Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi2Se3. By performing simultaneous spin, time, and angle-resolved photoemission spectroscopy, we map the spin-polarized unoccupied electronic structure and identify a surface resonance which is distinct from the topological surface state, yet shares a similar spin-orbital texture with opposite orientation. Its momentum dependence and spin texture imply an intimate connection with the topological surface state. Calculations show these two distinct states can emerge from trivial Rashba-like states that change topology through the spin-orbit-induced band inversion. This work thus provides a compelling view of the coevolution of surface states through a topological phase transition, enabled by the unique capability of directly measuring the spin-polarized unoccupied band structure. PMID:27739428

Designing spin-channel geometries for entanglement distribution

NASA Astrophysics Data System (ADS)

Levi, E. K.; Kirton, P. G.; Lovett, B. W.

2016-09-01

We investigate different geometries of spin-1/2 nitrogen impurity channels for distributing entanglement between pairs of remote nitrogen vacancy centers (NVs) in diamond. To go beyond the system size limits imposed by directly solving the master equation, we implement a matrix product operator method to describe the open system dynamics. In so doing, we provide an early demonstration of how the time-evolving block decimation algorithm can be used for answering a problem related to a real physical system that could not be accessed by other methods. For a fixed NV separation there is an interplay between incoherent impurity spin decay and coherent entanglement transfer: Long-transfer-time, few-spin systems experience strong dephasing that can be overcome by increasing the number of spins in the channel. We examine how missing spins and disorder in the coupling strengths affect the dynamics, finding that in some regimes a spin ladder is a more effective conduit for information than a single-spin chain.

High Spin States in ^24Mg

NASA Astrophysics Data System (ADS)

Schwartz, J.; Lister, C. J.; Wuosmaa, A.; Betts, R. R.; Blumenthal, D.; Carpenter, M. P.; Davids, C. N.; Fischer, S. M.; Hackman, G.; Janssens, R. V. F.

1996-05-01

The ^12C(^16O,α)^24Mg reaction was used at 51.5MeV to populate high angular momentum states in ^24Mg. Gamma-rays de-exciting high spin states were detected in a 20 detector spectrometer (the AYE-ball) triggered by the ANL Fragment Mass Analyser (FMA). Channel selection, through detection of ^24Mg nuclei with the appropriate time of flight, was excellent. All the known decays from high spin states were seen in a few hours, with the exception of the 5.04 MeV γ-decay of the J^π=9^- state at 16.904 MeV footnote A.E.Smith et al., Phys. Lett. \\underlineB176, (1986)292. which could not be confirmed. The potential of the technique for studying the radiative decay of states with very high spin in light nuclei will be discussed.

High-spin states in neutron-deficient nuclei near A=80

NASA Astrophysics Data System (ADS)

Theisen, L. V.; Tabor, S. L.; Medsker, L. R.; Neuschaefer, G.; Fry, L. H., Jr.; Clements, J. S.

1982-03-01

In-beam γ-ray spectroscopy with the reactions 54Fe + 28Si and 56Fe + 28Si at beam energies from 80 to 99 MeV were used to study high-spin states in neutron-deficient nuclei in the mass A~80 region. Measurements of γ-ray energies, intensities, angular distributions, excitation functions, and γ-γ coincidences were used to assign new levels in 79Rb and 80Sr. For the first time, high-spin states in 81Sr have been observed. NUCLEAR REACTIONS 56Fe(28Si,xpynγ) and 54Fe(28Si,xpynγ) Elab=80-99 MeV; measured Eγ, Iγ, γ-γ coincidences, σ(Eγ,E), and σ(Eγ,θ) 79Rb, 80Sr, and 81Sr deduced levels, Jπ. Enriched targets.

Equal-Spin Andreev Reflection on Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor.

PubMed

Matsuo, Sadashige; Ueda, Kento; Baba, Shoji; Kamata, Hiroshi; Tateno, Mizuki; Shabani, Javad; Palmstrøm, Christopher J; Tarucha, Seigo

2018-02-22

The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.

Spin-Forbidden Reactions: Adiabatic Transition States Using Spin-Orbit Coupled Density Functional Theory.

PubMed

Gaggioli, Carlo Alberto; Belpassi, Leonardo; Tarantelli, Francesco; Harvey, Jeremy N; Belanzoni, Paola

2018-04-06

A spin-forbidden chemical reaction involves a change in the total electronic spin state from reactants to products. The mechanistic study is challenging because such a reaction does not occur on a single diabatic potential energy surface (PES), but rather on two (or multiple) spin diabatic PESs. One possible approach is to calculate the so-called "minimum energy crossing point" (MECP) between the diabatic PESs, which however is not a stationary point. Inclusion of spin-orbit coupling between spin states (SOC approach) allows the reaction to occur on a single adiabatic PES, in which a transition state (TS SOC) as well as activation free energy can be calculated. This Concept article summarizes a previously published application in which, for the first time, the SOC effects, using spin-orbit ZORA Hamiltonian within density functional theory (DFT) framework, are included and account for the mechanism of a spin-forbidden reaction in gold chemistry. The merits of the MECP and TS SOC approaches and the accuracy of the results are compared, considering both our recent calculations on molecular oxygen addition to gold(I)-hydride complexes and new calculations for the prototype spin-forbidden N 2 O and N 2 Se dissociation reactions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Entanglement in a solid-state spin ensemble.

PubMed

Simmons, Stephanie; Brown, Richard M; Riemann, Helge; Abrosimov, Nikolai V; Becker, Peter; Pohl, Hans-Joachim; Thewalt, Mike L W; Itoh, Kohei M; Morton, John J L

2011-02-03

Entanglement is the quintessential quantum phenomenon. It is a necessary ingredient in most emerging quantum technologies, including quantum repeaters, quantum information processing and the strongest forms of quantum cryptography. Spin ensembles, such as those used in liquid-state nuclear magnetic resonance, have been important for the development of quantum control methods. However, these demonstrations contain no entanglement and ultimately constitute classical simulations of quantum algorithms. Here we report the on-demand generation of entanglement between an ensemble of electron and nuclear spins in isotopically engineered, phosphorus-doped silicon. We combined high-field (3.4 T), low-temperature (2.9 K) electron spin resonance with hyperpolarization of the (31)P nuclear spin to obtain an initial state of sufficient purity to create a non-classical, inseparable state. The state was verified using density matrix tomography based on geometric phase gates, and had a fidelity of 98% relative to the ideal state at this field and temperature. The entanglement operation was performed simultaneously, with high fidelity, on 10(10) spin pairs; this fulfils one of the essential requirements for a silicon-based quantum information processor.

Correlations and Werner states in finite spin linear arrays

NASA Astrophysics Data System (ADS)

Wells, P. R.; Chaves, C. M.; d'Albuquerque e Castro, J.; Koiller, Belita

2013-10-01

Pairwise quantum correlations in the ground state of an N-spins antiferromagnetic Heisenberg chain are investigated. By varying the exchange coupling between two neighboring sites, it is possible to reversibly drive spins from entangled to disentangled states. For even N, the two-spin density matrix is written in the form of a Werner state, allowing identification of its single parameter with the usual spin-spin correlation function. The N = 4 chain is identified as a promising system for practical demonstrations of non-classical correlations and the realization of Werner states in familiar condensed matter systems. Fabrication and measurement ingredients are within current capabilities.

π Spin Berry Phase in a Quantum-Spin-Hall-Insulator-Based Interferometer: Evidence for the Helical Spin Texture of the Edge States

NASA Astrophysics Data System (ADS)

Chen, Wei; Deng, Wei-Yin; Hou, Jing-Min; Shi, D. N.; Sheng, L.; Xing, D. Y.

2016-08-01

The quantum spin Hall insulator is characterized by helical edge states, with the spin polarization of the electron being locked to its direction of motion. Although the edge-state conduction has been observed, unambiguous evidence of the helical spin texture is still lacking. Here, we investigate the coherent edge-state transport in an interference loop pinched by two point contacts. Because of the helical character, the forward interedge scattering enforces a π spin rotation. Two successive processes can only produce a nontrivial 2 π or trivial 0 spin rotation, which can be controlled by the Rashba spin-orbit coupling. The nontrivial spin rotation results in a geometric π Berry phase, which can be detected by a π phase shift of the conductance oscillation relative to the trivial case. Our results provide smoking gun evidence for the helical spin texture of the edge states. Moreover, it also provides the opportunity to all electrically explore the trajectory-dependent spin Berry phase in condensed matter.

Spin Solid versus Magnetic Charge Ordered State in Artificial Honeycomb Lattice of Connected Elements

PubMed Central

Glavic, Artur; Summers, Brock; Dahal, Ashutosh; Kline, Joseph; Van Herck, Walter; Sukhov, Alexander; Ernst, Arthur

2018-01-01

Abstract The nature of magnetic correlation at low temperature in two‐dimensional artificial magnetic honeycomb lattice is a strongly debated issue. While theoretical researches suggest that the system will develop a novel zero entropy spin solid state as T → 0 K, a confirmation to this effect in artificial honeycomb lattice of connected elements is lacking. This study reports on the investigation of magnetic correlation in newly designed artificial permalloy honeycomb lattice of ultrasmall elements, with a typical length of ≈12 nm, using neutron scattering measurements and temperature‐dependent micromagnetic simulations. Numerical modeling of the polarized neutron reflectometry data elucidates the temperature‐dependent evolution of spin correlation in this system. As temperature reduces to ≈7 K, the system tends to develop novel spin solid state, manifested by the alternating distribution of magnetic vortex loops of opposite chiralities. Experimental results are complemented by temperature‐dependent micromagnetic simulations that confirm the dominance of spin solid state over local magnetic charge ordered state in the artificial honeycomb lattice with connected elements. These results enable a direct investigation of novel spin solid correlation in the connected honeycomb geometry of 2D artificial structure. PMID:29721429

Dynamic spin injection into a quantum well coupled to a spin-split bound state

NASA Astrophysics Data System (ADS)

Maslova, N. S.; Rozhansky, I. V.; Mantsevich, V. N.; Arseyev, P. I.; Averkiev, N. S.; Lähderanta, E.

2018-05-01

We present a theoretical analysis of dynamic spin injection due to spin-dependent tunneling between a quantum well (QW) and a bound state split in spin projection due to an exchange interaction or external magnetic field. We focus on the impact of Coulomb correlations at the bound state on spin polarization and sheet density kinetics of the charge carriers in the QW. The theoretical approach is based on kinetic equations for the electron occupation numbers taking into account high order correlation functions for the bound state electrons. It is shown that the on-site Coulomb repulsion leads to an enhanced dynamic spin polarization of the electrons in the QW and a delay in the carriers tunneling into the bound state. The interplay of these two effects leads to nontrivial dependence of the spin polarization degree, which can be probed experimentally using time-resolved photoluminescence experiments. It is demonstrated that the influence of the Coulomb interactions can be controlled by adjusting the relaxation rates. These findings open a new way of studying the Hubbard-like electron interactions experimentally.

Investigation of high spin states in 133Cs

NASA Astrophysics Data System (ADS)

Xu, Q.; Xiao, Z. G.; Zhu, S. J.; Qi, C.; Jia, H.; Qi, B.; Wang, R. S.; Cheng, W. J.; Zhang, Y.; Yi, H.; Lü, L. M.; Wang, Y. J.; Li, H. J.; Huang, Y.; Zhang, Z.; Wu, X. G.; Li, C. B.; Zheng, Y.; Chen, Q. M.; Zhou, W. K.; Li, G. S.

2018-05-01

High spin states in 133Cs nucleus have been studied with the reaction 130Te (7Li, 4n) at a beam energy of 38 MeV. The level scheme has been expanded with spin up to 31/2 \\hbar. Compared with a recent paper, ground state band and other two collective band structures at lower spin states have been confirmed. Another collective band structure at higher spin states as well as some levels and transitions are updated. Compared with the experimental data, large-scale shell model and tilted axis cranking model calculations have been carried out. The results show that the band-head configuration of yrast band based on 7/2+ ground state and the side band built on the 5/2+ state are a pair of pseudospin partner states with π \\tilde{f}_{7/2,5/2}. The negative parity band based on 1071.5 keV level originates from π h_{11/2} orbital. Another band built on 2642.9 keV level at high spin states has been proposed with oblate deformation. Other characteristics for these bands were also discussed.

Magnetic field sensors using 13-spin cat states

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

Simmons, Stephanie; Karlen, Steven D.; Jones, Jonathan A.

2010-08-15

Measurement devices could benefit from entangled correlations to yield a measurement sensitivity approaching the physical Heisenberg limit. Building upon previous magnetometric work using pseudoentangled spin states in solution-state NMR, we present two conceptual advancements to better prepare and interpret the pseudoentanglement resource. We apply these to a 13-spin cat state to measure the local magnetic field with a 12.2 sensitivity increase over an equivalent number of isolated spins.

Spin State Equilibria of Asteroids due to YORP Effects

NASA Astrophysics Data System (ADS)

Golubov, Oleksiy; Scheeres, Daniel J.; Lipatova, Veronika

2016-05-01

Spins of small asteroids are controlled by the Yarkovsky--O'Keefe--Radzievskii--Paddack (YORP) effect. The normal version of this effect has two components: the axial component alters the rotation rate, while the obliquity component alters the obliquity. Under this model the rotation state of an asteroid can be described in a phase plane with the rotation rate along the polar radius and the obliquity as the polar angle. The YORP effect induces a phase flow in this plane, which determines the distribution of asteroid rotation rates and obliquities.We study the properties of this phase flow for several typical cases. Some phase flows have stable attractors, while in others all trajectories go to very small or large rotation rates. In the simplest case of zero thermal inertia approximate analytical solutions to dynamics equations are possible. Including thermal inertia and the Tangential YORP effect makes the possible evolutionary scenarios much more diverse. We study possible evolution paths and classify the most general trends. Also we discuss possible implications for the distribution of asteroid rotation rates and obliquities.A special emphasis is put on asteroid (25143) Itokawa, whose shape model is well determined, but who's measured YORP acceleration does not agree with the predictions of normal YORP. We show that Itokawa's rotational state can be explained by the presence of tangential YORP and that it may be in or close to a stable spin state equilibrium. The implications of such states will be discussed.

Spin-polarized confined states in Ag films on Fe(110)

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

Moras, Paolo; Bihlmayer, G.; Vescovo, Elio

Spin- and angle-resolved photoemission spectroscopy of thin Ag(111) films on ferromagnetic Fe(110) shows a series of spin-polarized peaks. These features derive from Ag sp-bands, which form quantum well states and resonances due to confinement by a spin-dependent interface potential barrier. The spin-up states are broader and located at higher binding energy than the corresponding spin-down states at Gamma, although the differences attenuate near the Fermi level. The spin-down states display multiple gap openings, which interrupt their parabolic-like dispersion. As a result, first-principles calculations attribute these findings to the symmetry- and spin-selective hybridization of the Ag states with the exchange-split bandsmore » of the substrate.« less

Spin-polarized confined states in Ag films on Fe(110)

DOE PAGES

Moras, Paolo; Bihlmayer, G.; Vescovo, Elio; ...

2017-11-16

Spin- and angle-resolved photoemission spectroscopy of thin Ag(111) films on ferromagnetic Fe(110) shows a series of spin-polarized peaks. These features derive from Ag sp-bands, which form quantum well states and resonances due to confinement by a spin-dependent interface potential barrier. The spin-up states are broader and located at higher binding energy than the corresponding spin-down states at Gamma, although the differences attenuate near the Fermi level. The spin-down states display multiple gap openings, which interrupt their parabolic-like dispersion. As a result, first-principles calculations attribute these findings to the symmetry- and spin-selective hybridization of the Ag states with the exchange-split bandsmore » of the substrate.« less

Matter distribution and spin-orbit force in spherical nuclei

NASA Astrophysics Data System (ADS)

Co', G.; Anguiano, M.; De Donno, V.; Lallena, A. M.

2018-03-01

We investigate the possibility that some nuclei show density distributions with a depletion in the center, a semibubble structure, by using a Hartree-Fock plus Bardeen-Cooper-Schrieffer approach. We separately study the proton, neutron, and matter distributions in 37 spherical nuclei mainly in the s -d shell region. We found a relation between the semibubble structure and the energy splitting of spin-orbit partner single particle levels. The presence of semibubble structure reduces this splitting, and we study its consequences on the excitation spectrum of the nuclei under investigation by using a quasiparticle random-phase-approximation approach. The excitation energies of the low-lying 4+ states can be related to the presence of semibubble structure in nuclei.

Chiral filtration-induced spin/valley polarization in silicene line defects

NASA Astrophysics Data System (ADS)

Ren, Chongdan; Zhou, Benhu; Sun, Minglei; Wang, Sake; Li, Yunfang; Tian, Hongyu; Lu, Weitao

2018-06-01

The spin/valley polarization in silicene with extended line defects is investigated according to the chiral filtration mechanism. It is shown that the inner-built quantum Hall pseudo-edge states with identical chirality can serve as a chiral filter with a weak magnetic field and that the transmission process is restrained/strengthened for chiral states with reversed/identical chirality. With two parallel line defects, which act as natural chiral filtration, the filter effect is greatly enhanced, and 100% spin/valley polarization can be achieved.

Magnetoelectric Effect in a Spin-State Transition System

NASA Astrophysics Data System (ADS)

Naka, Makoto; Mizoguchi, Eriko; Nasu, Joji; Ishihara, Sumio

2018-06-01

Magnetic, dielectric, and magnetoelectric properties in a spin-state transition system are examined, motivated by the recent discovery of multiferroic behavior in a cobalt oxide. We construct an effective model Hamiltonian on the basis of the two-orbital Hubbard model, in which the spin-state degrees of freedom in magnetic ions couple with ferroelectric-type lattice distortions. A phase transition occurs from the high-temperature low-spin phase to the low-temperature high-spin ferroelectric phase with an accompanying increase in spin entropy. The calculated results are consistent with the experimental pressure-temperature phase diagram. We predict the magnetic-field induced electric polarization in the low-spin paraelectric phase near the ferroelectric phase boundary.

Spin-state responses to light impurity substitution in low-spin perovskite LaCoO3

NASA Astrophysics Data System (ADS)

Tomiyasu, Keisuke; Kubota, Yuuki; Shimomura, Saya; Onodera, Mitsugi; Koyama, Syun-Ichi; Nojima, Tsutomu; Ishihara, Sumio; Nakao, Hironori; Murakami, Youichi

2013-06-01

We studied the spin-state responses to light impurity substitution in low-spin perovskite LaCoO3 (Co3+: d6) through magnetization, x-ray fluorescence, and electrical resistivity measurements of single-crystal LaCo0.99M0.01O3 (M = Cr, Mn, Fe, Ni). In the magnetization curves measured at 1.8 K, a change in the spin-state was not observed for Cr, Mn, or Fe substitution but was observed for Ni substitution. Strong magnetic anisotropy was also found in the Ni-substituted sample. The fluorescence measurements revealed that the valences were roughly estimated to be Cr3+, Mn(4-δ)+, Fe(3+δ')+, and Ni3+. From the observed chemical trends, we propose that the chemical potential is a key factor in inducing the change of the low-spin state. By expanding a model of the ferromagnetic spin-state heptamer generated by hole doping [Podlesnyak , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.247603 101, 247603 (2008)], the emergence of highly anisotropic spin-state molecular ferromagnets induced by low-spin Ni3+ with Jahn-Teller activity is suggested. We also discuss applicability of the present results to other materials with Fe (d6).

Complete tomography of a high-fidelity solid-state entangled spin-photon qubit pair.

PubMed

De Greve, Kristiaan; McMahon, Peter L; Yu, Leo; Pelc, Jason S; Jones, Cody; Natarajan, Chandra M; Kim, Na Young; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Kamp, Martin; Höfling, Sven; Hadfield, Robert H; Forchel, Alfred; Fejer, M M; Yamamoto, Yoshihisa

2013-01-01

Entanglement between stationary quantum memories and photonic qubits is crucial for future quantum communication networks. Although high-fidelity spin-photon entanglement was demonstrated in well-isolated atomic and ionic systems, in the solid-state, where massively parallel, scalable networks are most realistically conceivable, entanglement fidelities are typically limited due to intrinsic environmental interactions. Distilling high-fidelity entangled pairs from lower-fidelity precursors can act as a remedy, but the required overhead scales unfavourably with the initial entanglement fidelity. With spin-photon entanglement as a crucial building block for entangling quantum network nodes, obtaining high-fidelity entangled pairs becomes imperative for practical realization of such networks. Here we report the first results of complete state tomography of a solid-state spin-photon-polarization-entangled qubit pair, using a single electron-charged indium arsenide quantum dot. We demonstrate record-high fidelity in the solid-state of well over 90%, and the first (99.9%-confidence) achievement of a fidelity that will unambiguously allow for entanglement distribution in solid-state quantum repeater networks.

Solution of the Lindblad equation for spin helix states.

PubMed

Popkov, V; Schütz, G M

2017-04-01

Using Lindblad dynamics we study quantum spin systems with dissipative boundary dynamics that generate a stationary nonequilibrium state with a nonvanishing spin current that is locally conserved except at the boundaries. We demonstrate that with suitably chosen boundary target states one can solve the many-body Lindblad equation exactly in any dimension. As solution we obtain pure states at any finite value of the dissipation strength and any system size. They are characterized by a helical stationary magnetization profile and a ballistic spin current which is independent of system size, even when the quantum spin system is not integrable. These results are derived in explicit form for the one-dimensional spin-1/2 Heisenberg chain and its higher-spin generalizations, which include the integrable spin-1 Zamolodchikov-Fateev model and the biquadratic Heisenberg chain.

Proton spin structure from measurable parton distributions.

PubMed

Ji, Xiangdong; Xiong, Xiaonu; Yuan, Feng

2012-10-12

We present a systematic study of the proton spin structure in terms of measurable parton distributions. For a transversely polarized proton, we derive a polarization sum rule from the leading generalized parton distributions appearing in hard exclusive processes. For a longitudinally polarized proton, we obtain a helicity decomposition from well-known quark and gluon helicity distributions and orbital angular-momentum contributions. The latter are shown to be related to measurable subleading generalized parton distributions and quantum-phase space Wigner distributions.

Optimization of identity operation in NMR spectroscopy via genetic algorithm: Application to the TEDOR experiment

NASA Astrophysics Data System (ADS)

Manu, V. S.; Veglia, Gianluigi

2016-12-01

Identity operation in the form of π pulses is widely used in NMR spectroscopy. For an isolated single spin system, a sequence of even number of π pulses performs an identity operation, leaving the spin state essentially unaltered. For multi-spin systems, trains of π pulses with appropriate phases and time delays modulate the spin Hamiltonian to perform operations such as decoupling and recoupling. However, experimental imperfections often jeopardize the outcome, leading to severe losses in sensitivity. Here, we demonstrate that a newly designed Genetic Algorithm (GA) is able to optimize a train of π pulses, resulting in a robust identity operation. As proof-of-concept, we optimized the recoupling sequence in the transferred-echo double-resonance (TEDOR) pulse sequence, a key experiment in biological magic angle spinning (MAS) solid-state NMR for measuring multiple carbon-nitrogen distances. The GA modified TEDOR (GMO-TEDOR) experiment with improved recoupling efficiency results in a net gain of sensitivity up to 28% as tested on a uniformly 13C, 15N labeled microcrystalline ubiquitin sample. The robust identity operation achieved via GA paves the way for the optimization of several other pulse sequences used for both solid- and liquid-state NMR used for decoupling, recoupling, and relaxation experiments.

Energy Spectrum for the System, of N Ising Spins with Identical, Spin-Spin Coupling K/N - Anatomy of Phase Transition

NASA Astrophysics Data System (ADS)

Czachor, A.

2008-04-01

For the Kittel-Shore-Kac interspin coupling K/N between N Ising spins the ferromagnetic phase transition in specific heat vs. T plot has appeared in literature as a purely mathematical phenomenon, via the exact calculation of the sum of states Z(T) and subsequent differentiations with respect to temperature T. Physical nature of the transition remains in such derivation invisible. As it is expected to be related to the interaction/temperature competition in populating energy levels of the system, in this paper we construct the density of energy states D(E) (or energy spectrum) of such systems, both for the ferromagnetic (K > 0) and antiferromagnetic (K < 0) coupling between spins. This allows one to see the essence of the difference between these systems as related to the discrete vs. quasi-continuous shape of the spectra at low energy states.

Spin state switching in iron coordination compounds

PubMed Central

Gaspar, Ana B; Garcia, Yann

2013-01-01

Summary The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices. The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property. PMID:23504535

Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

NASA Astrophysics Data System (ADS)

Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.

2015-11-01

We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7-Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with the

Tuning Interfacial States Using Organic Molecules as Spin Filters

NASA Astrophysics Data System (ADS)

Deloach, Andrew; Wang, Jingying; Papa, Christopher M.; Myahkostupov, Mykhaylo; Castellano, Felix N.; Dougherty, Daniel B.; Jiang, Wei; Liu, Feng

Organic semiconductors are known to have long spin relaxation times which makes them a good candidate for spintronics. However, an issue with these materials is that at metal-organic interfaces there is a conductivity mismatch problem that suppresses spin injection. To overcome this, orbital mixing at the interface can be tuned with an organic spacer layer to promote the formation of spin polarized interface states. These states act as a ``spin filters'' and have been proposed as an explanation for the large tunneling magnetoresistance seen in devices using tris-(8-hydroxyquinolate)-aluminum(Alq3). Here, we show that the spin polarized interface states can be tuned from metallic to resistive by subtle changes in molecular orbitals. This is done using spin polarized scanning tunneling microscopy with three different tris-(8-hydroxyquinolate) compounds: aluminum, chromium, and iron. Differences in d-orbital mixing results in different mechanisms of interfacial coupling, giving rise to metallic or resistive interface states. Supported by the U.S. DoE award No. DE-SC0010324.

Waiting time distribution revealing the internal spin dynamics in a double quantum dot

NASA Astrophysics Data System (ADS)

Ptaszyński, Krzysztof

2017-07-01

Waiting time distribution and the zero-frequency full counting statistics of unidirectional electron transport through a double quantum dot molecule attached to spin-polarized leads are analyzed using the quantum master equation. The waiting time distribution exhibits a nontrivial dependence on the value of the exchange coupling between the dots and the gradient of the applied magnetic field, which reveals the oscillations between the spin states of the molecule. The zero-frequency full counting statistics, on the other hand, is independent of the aforementioned quantities, thus giving no insight into the internal dynamics. The fact that the waiting time distribution and the zero-frequency full counting statistics give a nonequivalent information is associated with two factors. Firstly, it can be explained by the sensitivity to different timescales of the dynamics of the system. Secondly, it is associated with the presence of the correlation between subsequent waiting times, which makes the renewal theory, relating the full counting statistics and the waiting time distribution, no longer applicable. The study highlights the particular usefulness of the waiting time distribution for the analysis of the internal dynamics of mesoscopic systems.

Rigorous decoupling between edge states in frustrated spin chains and ladders

NASA Astrophysics Data System (ADS)

Chepiga, Natalia; Mila, Frédéric

2018-05-01

We investigate the occurrence of exact zero modes in one-dimensional quantum magnets of finite length that possess edge states. Building on conclusions first reached in the context of the spin-1/2 X Y chain in a field and then for the spin-1 J1-J2 Heisenberg model, we show that the development of incommensurate correlations in the bulk invariably leads to oscillations in the sign of the coupling between edge states, and hence to exact zero energy modes at the crossing points where the coupling between the edge states rigorously vanishes. This is true regardless of the origin of the frustration (e.g., next-nearest-neighbor coupling or biquadratic coupling for the spin-1 chain), of the value of the bulk spin (we report on spin-1/2, spin-1, and spin-2 examples), and of the value of the edge-state emergent spin (spin-1/2 or spin-1).

Relativistic distribution function for particles with spin at local thermodynamical equilibrium

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

Becattini, F., E-mail: becattini@fi.infn.it; INFN Sezione di Firenze, Florence; Universität Frankfurt, Frankfurt am Main

2013-11-15

We present an extension of relativistic single-particle distribution function for weakly interacting particles at local thermodynamical equilibrium including spin degrees of freedom, for massive spin 1/2 particles. We infer, on the basis of the global equilibrium case, that at local thermodynamical equilibrium particles acquire a net polarization proportional to the vorticity of the inverse temperature four-vector field. The obtained formula for polarization also implies that a steady gradient of temperature entails a polarization orthogonal to particle momentum. The single-particle distribution function in momentum space extends the so-called Cooper–Frye formula to particles with spin 1/2 and allows us to predict theirmore » polarization in relativistic heavy ion collisions at the freeze-out. -- Highlights: •Single-particle distribution function in local thermodynamical equilibrium with spin. •Polarization of spin 1/2 particles in a fluid at local thermodynamical equilibrium. •Prediction of a new effect: a steady gradient of temperature induces a polarization. •Application to the calculation of polarization in relativistic heavy ion collisions.« less

Physics and application of persistent spin helix state in semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Kohda, Makoto; Salis, Gian

2017-07-01

In order to utilize the spin degree of freedom in semiconductors, control of spin states and transfer of the spin information are fundamental requirements for future spintronic devices and quantum computing. Spin orbit (SO) interaction generates an effective magnetic field for moving electrons and enables spin generation, spin manipulation and spin detection without using external magnetic field and magnetic materials. However, spin relaxation also takes place due to a momentum dependent SO-induced effective magnetic field. As a result, SO interaction is considered to be a double-edged sword facilitating spin control but preventing spin transport over long distances. The persistent spin helix (PSH) state solves this problem since uniaxial alignment of the SO field with SU(2) symmetry enables the suppression of spin relaxation while spin precession can still be controlled. Consequently, understanding the PSH becomes an important step towards future spintronic technologies for classical and quantum applications. Here, we review recent progress of PSH in semiconductor heterostructures and its device application. Fundamental physics of SO interaction and the conditions of a PSH state in semiconductor heterostructures are discussed. We introduce experimental techniques to observe a PSH and explain both optical and electrical measurements for detecting a long spin relaxation time and the formation of a helical spin texture. After emphasizing the bulk Dresselhaus SO coefficient γ, the application of PSH states for spin transistors and logic circuits are discussed.

Distribution of localized states from fine analysis of electron spin resonance spectra of organic semiconductors: Physical meaning and methodology

NASA Astrophysics Data System (ADS)

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

2012-02-01

We develop an analytical method for the processing of electron spin resonance (ESR) spectra. The goal is to obtain the distributions of trapped carriers over both their degree of localization and their binding energy in semiconductor crystals or films composed of regularly aligned organic molecules [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.056602 104, 056602 (2010)]. Our method has two steps. We first carry out a fine analysis of the shape of the ESR spectra due to the trapped carriers; this reveals the distribution of the trap density of the states over the degree of localization. This analysis is based on the reasonable assumption that the linewidth of the trapped carriers is predetermined by their degree of localization because of the hyperfine mechanism. We then transform the distribution over the degree of localization into a distribution over the binding energies. The transformation uses the relationships between the binding energies and the localization parameters of the trapped carriers. The particular relation for the system under study is obtained by the Holstein model for trapped polarons using a diagrammatic Monte Carlo analysis. We illustrate the application of the method to pentacene organic thin-film transistors.

Excited-State Spin Manipulation and Intrinsic Nuclear Spin Memory using Single Nitrogen-Vacancy Centers in Diamond

NASA Astrophysics Data System (ADS)

Fuchs, Gregory

2011-03-01

Nitrogen vacancy (NV) center spins in diamond have emerged as a promising solid-state system for quantum information processing and precision metrology at room temperature. Understanding and developing the built-in resources of this defect center for quantum logic and memory is critical to achieving these goals. In the first case, we use nanosecond duration microwave manipulation to study the electronic spin of single NV centers in their orbital excited-state (ES). We demonstrate ES Rabi oscillations and use multi-pulse resonant control to differentiate between phonon-induced dephasing, orbital relaxation, and coherent electron-nuclear interactions. A second resource, the nuclear spin of the intrinsic nitrogen atom, may be an ideal candidate for a quantum memory due to both the long coherence of nuclear spins and their deterministic presence. We investigate coherent swaps between the NV center electronic spin state and the nuclear spin state of nitrogen using Landau-Zener transitions performed outside the asymptotic regime. The swap gates are generated using lithographically fabricated waveguides that form a high-bandwidth, two-axis vector magnet on the diamond substrate. These experiments provide tools for coherently manipulating and storing quantum information in a scalable solid-state system at room temperature. We gratefully acknowledge support from AFOSR, ARO, and DARPA.

Robust state transfer in the quantum spin channel via weak measurement and quantum measurement reversal

NASA Astrophysics Data System (ADS)

He, Zhi; Yao, Chunmei; Zou, Jian

2013-10-01

Using the weak measurement (WM) and quantum measurement reversal (QMR) approach, robust state transfer and entanglement distribution can be realized in the spin-(1)/(2) Heisenberg chain. We find that the ultrahigh fidelity and long distance of quantum state transfer with certain success probability can be obtained using proper WM and QMR, i.e., the average fidelity of a general pure state from 80% to almost 100%, which is almost size independent. We also find that the distance and quality of entanglement distribution for the Bell state and the general Werner mixed state can be obviously improved by the WM and QMR approach.

Spin Axis Distribution of the Hungaria Asteroids via Lightcurve Inversion

NASA Astrophysics Data System (ADS)

Warner, Brian D.

2015-05-01

In the past decade or so, the influence on small asteroids of the YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect, which is the asymmetric thermal emission of received sunlight, has been firmly established. The two strongest pieces of evidence are the nearly flat distribution of rotation rates of small asteroids and the distribution of spin axes (poles). YORP theory says that the spin axes, barring outside influences, are eventually forced to low obliquities, i.e., the poles are located near the north or south ecliptic poles. This would seem natural for objects with low orbital inclinations. However, for objects with high orbital inclinations, such as the Hungarias, there are some questions if this would still be the case. The authors and other observers have accumulated dense lightcurves of the Hungaria asteroids for more than a decade. The combination of these dense lightcurves and sparse data from asteroid search surveys has allowed using lightcurve inversion techniques to determine the spin axes for almost 75 Hungaria asteroids. The results confirm earlier works that show an anisotropic distribution of spin axes that favors the ecliptic poles and, as predicted for the Hungarias, a preponderance of retrograde rotators.

Epitaxial strain-mediated spin-state transitions: can we switch off magnetism?

NASA Astrophysics Data System (ADS)

Rondinelli, James; Spaldin, Nicola

2008-03-01

We use first-principles density functional theory calculations to explore spin-state transitions in epitaxially strained LaCoO3. While high-spin to low-spin state transitions in minerals are common in geophysics, where pressures can reach over 200 GPa, we explore whether heteroepitaxial strain can achieve similar transitions with moderate strain in thin films. LaCoO3 is known to undergo a low-spin (S=0, t2g^6eg^0) to intermediate-spin (S=1, t2g^5eg^1) or high-spin (S=2, t2g^4eg^2) state transition with increasing temperature, and thus makes it a promising candidate material for strain-mediated spin transitions. Here we discuss the physics of the low-spin transition and changes in the electronic structure of LaCoO3, most notably, the metal-insulator transition that accompanies the spin-state transitions with epitaxial strain. As thin film growth techniques continue to reach atomic-level precision, we suggest this is another approach for controlling magnetism in complex oxide heterostructures.

Spin-state crossover and low-temperature magnetic state in yttrium-doped Pr0.7Ca0.3CoO3

NASA Astrophysics Data System (ADS)

Knížek, K.; Hejtmánek, J.; Maryško, M.; Novák, P.; Šantavá, E.; Jirák, Z.; Naito, T.; Fujishiro, H.; de la Cruz, Clarina

2013-12-01

The structural and magnetic properties of two mixed-valence cobaltites with a formal population of 0.30 Co4+ ions per f.u., (Pr1-yYy)0.7Ca0.3CoO3 (y=0 and 0.15), have been studied down to very low temperatures by means of high-resolution neutron diffraction, SQUID magnetometry, and heat-capacity measurements. The results are interpreted within the scenario of the spin-state crossover from a room-temperature mixture of the intermediate-spin Co3+ and low-spin Co4+ (IS/LS) to the LS/LS mixture in the sample ground states. In contrast to the yttrium-free y=0 that retains the metallic-like character and exhibits ferromagnetic (FM) ordering below 55 K, the doped system y=0.15 undergoes a first-order metal-insulator transition at 132 K, during which not only the crossover to low-spin states but also a partial electron transfer from Pr3+ 4f to cobalt 3d states takes place simultaneously. Taking into account the nonmagnetic character of LS Co3+, such a valence shift electronic transition causes a magnetic dilution, formally to 0.12 LS Co4+ or 0.12 t2g hole spins per f.u., which is the reason for an insulating, highly nonuniform magnetic ground state without long-range order. Nevertheless, even in that case there exists a relatively strong molecular field distributed over all the crystal lattice. It is argued that the spontaneous FM order in y=0 and the existence of strong FM correlations in y=0.15 apparently contradict the single t2g band character of LS/LS phase. The explanation we suggest relies on a model of the defect-induced, itinerant hole-mediated magnetism, where the defects are identified with the magnetic high-spin Co3+ species stabilized near oxygen vacancies.

High spin states of 72-74Kr

NASA Astrophysics Data System (ADS)

Kaushik, M.; Kumawat, M.; Singh, U. K.; Saxena, G.

2018-05-01

A theoretical investigation has made on the structure of high spin states of 72-74Kr within the framework of cranked Hartree-Fock-Bogoliubov (CHFB) theory employing a pairing + quadrupole + hexadecapole model interaction. Dependence of shape with the spin, excitation energy, alignment of proton as well as neutron 0g9/2 orbital along with backbending phenomenon are discussed upto a high spin J = 26. We found reasonable agreement with the experimental values and other theoretical calculations.

Electrically tunable spin filtering for electron tunneling between spin-resolved quantum Hall edge states and a quantum dot

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

Kiyama, H., E-mail: kiyama@meso.t.u-tokyo.ac.jp; Fujita, T.; Teraoka, S.

2014-06-30

Spin filtering with electrically tunable efficiency is achieved for electron tunneling between a quantum dot and spin-resolved quantum Hall edge states by locally gating the two-dimensional electron gas (2DEG) leads near the tunnel junction to the dot. The local gating can change the potential gradient in the 2DEG and consequently the edge state separation. We use this technique to electrically control the ratio of the dot–edge state tunnel coupling between opposite spins and finally increase spin filtering efficiency up to 91%, the highest ever reported, by optimizing the local gating.

Fermionic spin liquid analysis of the paramagnetic state in volborthite

NASA Astrophysics Data System (ADS)

Chern, Li Ern; Schaffer, Robert; Sorn, Sopheak; Kim, Yong Baek

2017-10-01

Recently, thermal Hall effect has been observed in the paramagnetic state of volborthite, which consists of distorted kagome layers with S =1 /2 local moments. Despite the appearance of magnetic order below 1 K , the response to external magnetic field and unusual properties of the paramagnetic state above 1 K suggest possible realization of exotic quantum phases. Motivated by these discoveries, we investigate possible spin liquid phases with fermionic spinon excitations in a nonsymmorphic version of the kagome lattice, which belongs to the two-dimensional crystallographic group p 2 g g . This nonsymmorphic structure is consistent with the spin model obtained in the density functional theory calculation. Using projective symmetry group analysis and fermionic parton mean field theory, we identify twelve distinct Z2 spin liquid states, four of which are found to have correspondence in the eight Schwinger boson spin liquid states we classified earlier. We focus on the four fermionic states with bosonic counterpart and find that the spectrum of their corresponding root U (1 ) states features spinon Fermi surface. The existence of spinon Fermi surface in candidate spin liquid states may offer a possible explanation of the finite thermal Hall conductivity observed in volborthite.

Enhanced Spin Squeezing in Atomic Ensembles via Control of the Internal Spin States

NASA Astrophysics Data System (ADS)

Shojaee, Ezad; Norris, Leigh; Baragiola, Ben; Montano, Enrique; Hemmer, Daniel; Jessen, Poul; Deutsch, Ivan

2015-05-01

Abstract: We study the process by which the collective spin squeezing of an ensemble of Cesium atoms is enhanced by control of the internal spin state of the atoms. By increasing the initial atomic projection noise, one can enhance the Faraday interaction that entangles the atoms with a probe. The light acts as a quantum bus for creating atom-atom entanglement via measurement backaction. Further control can be used to transfer this entanglement to metrologically useful squeezing. We numerically simulate this protocol by a stochastic master equation, including QND measurement and optical pumping, which accounts for decoherence and transfer of coherences between magnetic sub-levels. We study the tradeoff between the enhanced entangling interaction and increased rates of decoherence for different initial state preparations. Under realistic conditions, we find that we can achieve squeezing with a ``CAT-State'' superpostion |F = 4, Mz = 4> + |F, Mz = -4> of ~ 9.9 dB and for the spin coherent state |F = 4, Mx = 4> of ~ 7.5 dB. The increased entanglement enabled by the CAT state preparation is partially, but not completely reduced by the increased fragility to decoherence. National Science Foundation.

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.

A Christian identity for the liberal state?

PubMed

Joppke, Christian

2013-12-01

It seems to be impossible for the liberal state to embrace a Christian identity, because 'liberalism' is exactly a device for separating state and religion. Discussing the implications of a recent decision of the European Court of Human Rights, Lautsi v. Italy (2011), I argue that this is not necessarily so. If paired with a liberal commitment to pluralism, a Christian identity might even be more inclusive of minority religions than a narrowly 'liberal' state identity, which has been the dominant response in Western Europe to the challenge of immigrant diversity, especially that of Muslim origins. © London School of Economics and Political Science 2013.

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

The influence of further-neighbor spin-spin interaction on a ground state of 2D coupled spin-electron model in a magnetic field

NASA Astrophysics Data System (ADS)

Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej; Tomašovičová, Natália

2018-05-01

An exhaustive ground-state analysis of extended two-dimensional (2D) correlated spin-electron model consisting of the Ising spins localized on nodal lattice sites and mobile electrons delocalized over pairs of decorating sites is performed within the framework of rigorous analytical calculations. The investigated model, defined on an arbitrary 2D doubly decorated lattice, takes into account the kinetic energy of mobile electrons, the nearest-neighbor Ising coupling between the localized spins and mobile electrons, the further-neighbor Ising coupling between the localized spins and the Zeeman energy. The ground-state phase diagrams are examined for a wide range of model parameters for both ferromagnetic as well as antiferromagnetic interaction between the nodal Ising spins and non-zero value of external magnetic field. It is found that non-zero values of further-neighbor interaction leads to a formation of new quantum states as a consequence of competition between all considered interaction terms. Moreover, the new quantum states are accompanied with different magnetic features and thus, several kinds of field-driven phase transitions are observed.

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

Spin-adapted matrix product states and operators

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

Keller, Sebastian, E-mail: sebastian.keller@phys.chem.ethz.ch; Reiher, Markus, E-mail: markus.reiher@phys.chem.ethz.ch

Matrix product states (MPSs) and matrix product operators (MPOs) allow an alternative formulation of the density matrix renormalization group algorithm introduced by White. Here, we describe how non-abelian spin symmetry can be exploited in MPSs and MPOs by virtue of the Wigner–Eckart theorem at the example of the spin-adapted quantum chemical Hamiltonian operator.

Spin-flop states in a synthetic antiferromagnet and variations of unidirectional anisotropy in FeMn-based spin valves

NASA Astrophysics Data System (ADS)

Milyaev, M. A.; Naumova, L. I.; Chernyshova, T. A.; Proglyado, V. V.; Kulesh, N. A.; Patrakov, E. I.; Kamenskii, I. Yu.; Ustinov, V. V.

2016-12-01

Spin valves with a synthetic antiferromagnet have been prepared by magnetron sputtering. Regularities of the formation of single- and two-phase spin-flop states in the synthetic antiferromagnet have been studied using magnetoresistance measurements and imaging the magnetic structure. A thermomagnetic treatment of spin valve in a field that corresponds to the single-phase spin-flop state of synthetic antiferromagnet was shown to allow us to obtain a magnetically sensitive material characterized by hysteresis-free field dependence of the magnetoresistance.

Reassessment of fission fragment angular distributions from continuum states in the context of transition-state theory

NASA Astrophysics Data System (ADS)

Vaz, Louis C.; Alexander, John M.

1983-07-01

Fission angular distributions have been studied for years and have been treated as classic examples of trasitions-state theory. Early work involving composite nuclei of relatively low excitation energy E ∗ (⪅35 MeV) and spin I (⪅25ħ) gave support to theory and delimited interesting properties of the transitions-state nuclei. More recent research on fusion fission and sequential fission after deeply inelastic reactions involves composite nuclei of much higher energies (⪅200 MeV) and spins (⪅100ħ). Extension of the basic ideas developed for low-spin nuclei requires detailed consideration of the role of these high spins and, in particular, the “spin window” for fussion. We have made empirical correlations of cross sections for evaporation residues and fission in order to get a description of this spin window. A systematic reanalysis has been made for fusion fission induced by H, He and heavier ions. Empirical correlations of K 20 (K 20 = {IeffT }/{h̷2}) are presented along with comparisons of Ieff to moments of inertia for saddle-point nuclei from the rotating liquid drop model. This model gives an excellent guide for the intermidiate spin zone (30⪅ I ⪅65), while strong shell and/or pairing effects are evident for excitations less than ⪅35 MeV. Observations of strong anisotropies for very high-spin systems signal the demise of certain approximation commonly made in the theory, and suggestions are made toward this end.

Yrare low-spin positive-parity states in N = 88 66 154 Dy

NASA Astrophysics Data System (ADS)

Zimba, G. L.; Bvumbi, S. P.; Masiteng, L. P.; Jones, P.; Sharpey-Schafer, J. F.; Majola, S. N. T.; Dinoko, T. S.; Shirinda, O.; Lawrie, J. J.; Easton, J. E.; Khumalo, N. A.; Msebi, L.; Mashita, P. I.; Papka, P.; Roux, D. G.; Negi, D.

2018-04-01

Low-spin positive-parity yrare states of 66 154 Dy88 were established using the 155Gd(3He,4n) reaction at a beam energy of E_{lab} = 37.5 MeV. The AFRODITE spectrometer array at iThemba LABS was used to record γγ coincidences and measure DCO ratios and polarisation asymmetries. The K^{π}=2+ γ band has been observed up to spin 13+ in the odd spins and to 12+ in the even spins. The staggering parameter S( I) of the γ band is compared to that found in other N = 88 isotones. Different behaviour of S( I) with increasing spin is observed for each of the isotones. We conjecture that the variation in S( I) is mainly due to mixing of the even-spin states with the same spin and parity states in neighbouring rotational bands. A second K^{π}=2+ band has been established up to a spin of 12+ in the even spins. We suggest that this is a γ band based on the J^{π} = 0+ state at Ex = 660.6 keV.

High spin states of 141Pm

NASA Astrophysics Data System (ADS)

Bhattacharyya, Sarmishtha; Chanda, Somen; Bhattacharjee, Tumpa; Basu, Swapan Kumar; Bhowmik, R. K.; Muralithar, S.; Singh, R. P.; Ghugre, S. S.

2004-01-01

The high spin states in the N=80 odd- A141Pm nucleus have been investigated by in-beam γ-spectroscopic techniques following the reaction 133Cs( 12C, 4n) 141Pm at E=65 MeV using a modest γ detector array, consisting of seven Compton-suppressed high purity germanium detectors and a multiplicity ball of 14 bismuth germanate elements. Thirty new γ rays have been assigned to 141Pm on the basis of γ-ray singles and γγ-coincidence data. The level scheme of 141Pm has been extended upto an excitation energy of 5.2 MeV and spin {35}/{2}ℏ and 16 new levels have been proposed. Spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced directional correlation orientation ratios for strong transitions. The meanlives of a few excited states have been determined from the pulsed beam- γγ coincidence data using the generalised centroid-shift method. The level structure is discussed in the light of known systematics of neighbouring N=80 isotonic nuclei.

Entangled spins and ghost-spins

NASA Astrophysics Data System (ADS)

Jatkar, Dileep P.; Narayan, K.

2017-09-01

We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

Spin polarized electronic states and spin textures at the surface of oxygen-deficient SrTiO3

NASA Astrophysics Data System (ADS)

Jeschke, Harald O.; Altmeyer, Michaela; Rozenberg, Marcelo; Gabay, Marc; Valenti, Roser

We investigate the electronic structure and spin texture at the (001) surface of SrTiO3 in the presence of oxygen vacancies by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic non-magnetic DFT calculations exhibit Rashba-like spin winding with a characteristic energy scale ~ 10 meV. However, when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ~ 100 meV at the Γ point. This energy scale is comparable to the observations in SARPES experiments performed on the two-dimensional electronic states confined near the (001) surface of SrTiO3. We find the spin polarized state to be the ground state of the system, and while magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft through grants SFB/TR 49 and FOR 1346.

Nonlocal Nuclear Spin Quieting in Quantum Dot Molecules: Optically Induced Extended Two-Electron Spin Coherence Time.

PubMed

Chow, Colin M; Ross, Aaron M; Kim, Danny; Gammon, Daniel; Bracker, Allan S; Sham, L J; Steel, Duncan G

2016-08-12

We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.

Nonlocal Nuclear Spin Quieting in Quantum Dot Molecules: Optically Induced Extended Two-Electron Spin Coherence Time

NASA Astrophysics Data System (ADS)

Chow, Colin M.; Ross, Aaron M.; Kim, Danny; Gammon, Daniel; Bracker, Allan S.; Sham, L. J.; Steel, Duncan G.

2016-08-01

We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.

Stochastic switching of TiO2-based memristive devices with identical initial memory states

PubMed Central

2014-01-01

In this work, we show that identical TiO2-based memristive devices that possess the same initial resistive states are only phenomenologically similar as their internal structures may vary significantly, which could render quite dissimilar switching dynamics. We experimentally demonstrated that the resistive switching of practical devices with similar initial states could occur at different programming stimuli cycles. We argue that similar memory states can be transcribed via numerous distinct active core states through the dissimilar reduced TiO2-x filamentary distributions. Our hypothesis was finally verified via simulated results of the memory state evolution, by taking into account dissimilar initial filamentary distribution. PMID:24994953

Chiral tunneling of topological states: towards the efficient generation of spin current using spin-momentum locking.

PubMed

Habib, K M Masum; Sajjad, Redwan N; Ghosh, Avik W

2015-05-01

We show that the interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D topological insulator (TI). Our calculations show that the chiral tunneling across a TI pn junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, gate-tunable spin-to-charge current ratio (∼20) at the reflected end. At the transmitted end, the ratio stays close to 1 and the electrons are completely spin polarized.

Holographic spin networks from tensor network states

NASA Astrophysics Data System (ADS)

Singh, Sukhwinder; McMahon, Nathan A.; Brennen, Gavin K.

2018-01-01

In the holographic correspondence of quantum gravity, a global on-site symmetry at the boundary generally translates to a local gauge symmetry in the bulk. We describe one way how the global boundary on-site symmetries can be gauged within the formalism of the multiscale renormalization ansatz (MERA), in light of the ongoing discussion between tensor networks and holography. We describe how to "lift" the MERA representation of the ground state of a generic one dimensional (1D) local Hamiltonian, which has a global on-site symmetry, to a dual quantum state of a 2D "bulk" lattice on which the symmetry appears gauged. The 2D bulk state decomposes in terms of spin network states, which label a basis in the gauge-invariant sector of the bulk lattice. This decomposition is instrumental to obtain expectation values of gauge-invariant observables in the bulk, and also reveals that the bulk state is generally entangled between the gauge and the remaining ("gravitational") bulk degrees of freedom that are not fixed by the symmetry. We present numerical results for ground states of several 1D critical spin chains to illustrate that the bulk entanglement potentially depends on the central charge of the underlying conformal field theory. We also discuss the possibility of emergent topological order in the bulk using a simple example, and also of emergent symmetries in the nongauge (gravitational) sector in the bulk. More broadly, our holographic model translates the MERA, a tensor network state, to a superposition of spin network states, as they appear in lattice gauge theories in one higher dimension.

In-Beam Studies of High Spin States in Mercury -182 and MERCURY-184

NASA Astrophysics Data System (ADS)

Bindra, Kanwarjit Singh

The high spin states in ^{182 }Hg were studied by using the reaction ^{154}Gd(^{32}S, 4n) at the Holifield Heavy Ion Research Facility. In addition, the in-beam gamma-rays in ^{183}Hg were identified for the first time using the reaction ^{155}Gd(^{32}S, 4n) at the Argonne BGO-FMA facility. Five new bands were observed for the first time in ^{182}Hg by studying the gamma-gamma coincidence relationships. The spins and parities of the nuclear levels were assigned on the basis of the measured ratios of directional correlations for oriented nuclei (DCO ratios). Shape co-existence similar to that observed in ^{184{-}186}Hg was established. The well deformed prolate band was extended to a state with tentative spin (20^+). The 2^+ state of the prolate band was identified at an energy of 548.6 keV which is higher in energy than in ^{184}Hg. A two parameter band mixing calculation yielded an interaction strength of 87 keV between the prolate 2^+ and the oblate 2^+ states. Four of the five new bands were found to be similar in behavior to ones seen in ^{184}Hg. An attempt was made to study the behavior of some of these bands at high spins by analyzing their kinematic and dynamic moments of inertia. The gamma-ray transitions in ^{183}Hg were identified from fragment-gamma and gamma-gamma coincidence measurements. A total of five bands of levels were identified and the spins and parities of the levels were assigned by comparing the level scheme of ^{138 }Hg obtained with that of ^ {185}Hg established previously. The interpretation of these bands in terms of associated quasi-particle configurations also relies on noted similarities with the structure of ^{185}Hg. Shape co-existence was established in ^{183}Hg as a result of this study. Two of the bands associated with the (624) 9/2^+ orbital were found to exhibit signature splitting, as expected for i _{13/2} excitations built on the prolate shape with moderate deformation. Two other bands which do not show signature splitting

Ground-state energies of the nonlinear sigma model and the Heisenberg spin chains

NASA Technical Reports Server (NTRS)

Zhang, Shoucheng; Schulz, H. J.; Ziman, Timothy

1989-01-01

A theorem on the O(3) nonlinear sigma model with the topological theta term is proved, which states that the ground-state energy at theta = pi is always higher than the ground-state energy at theta = 0, for the same value of the coupling constant g. Provided that the nonlinear sigma model gives the correct description for the Heisenberg spin chains in the large-s limit, this theorem makes a definite prediction relating the ground-state energies of the half-integer and the integer spin chains. The ground-state energies obtained from the exact Bethe ansatz solution for the spin-1/2 chain and the numerical diagonalization on the spin-1, spin-3/2, and spin-2 chains support this prediction.

Retrieving the ground state of spin glasses using thermal noise: Performance of quantum annealing at finite temperatures.

PubMed

Nishimura, Kohji; Nishimori, Hidetoshi; Ochoa, Andrew J; Katzgraber, Helmut G

2016-09-01

We study the problem to infer the ground state of a spin-glass Hamiltonian using data from another Hamiltonian with interactions disturbed by noise from the original Hamiltonian, motivated by the ground-state inference in quantum annealing on a noisy device. It is shown that the average Hamming distance between the inferred spin configuration and the true ground state is minimized when the temperature of the noisy system is kept at a finite value, and not at zero temperature. We present a spin-glass generalization of a well-established result that the ground state of a purely ferromagnetic Hamiltonian is best inferred at a finite temperature in the sense of smallest Hamming distance when the original ferromagnetic interactions are disturbed by noise. We use the numerical transfer-matrix method to establish the existence of an optimal finite temperature in one- and two-dimensional systems. Our numerical results are supported by mean-field calculations, which give an explicit expression of the optimal temperature to infer the spin-glass ground state as a function of variances of the distributions of the original interactions and the noise. The mean-field prediction is in qualitative agreement with numerical data. Implications on postprocessing of quantum annealing on a noisy device are discussed.

Memory-built-in quantum cloning in a hybrid solid-state spin register

NASA Astrophysics Data System (ADS)

Wang, W.-B.; Zu, C.; He, L.; Zhang, W.-G.; Duan, L.-M.

2015-07-01

As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude. The realization of a cloning machine with built-in quantum memory provides a key step for application of quantum cloning in quantum information science.

Memory-built-in quantum cloning in a hybrid solid-state spin register.

PubMed

Wang, W-B; Zu, C; He, L; Zhang, W-G; Duan, L-M

2015-07-16

As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude. The realization of a cloning machine with built-in quantum memory provides a key step for application of quantum cloning in quantum information science.

Memory-built-in quantum cloning in a hybrid solid-state spin register

PubMed Central

Wang, W.-B.; Zu, C.; He, L.; Zhang, W.-G.; Duan, L.-M.

2015-01-01

As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude. The realization of a cloning machine with built-in quantum memory provides a key step for application of quantum cloning in quantum information science. PMID:26178617

Spin distribution of evaporation residues formed in complete and incomplete fusion in 16O+154Sm system

NASA Astrophysics Data System (ADS)

Singh, D.; Linda, Sneha B.; Giri, Pankaj K.; Mahato, Amritraj; Tripathi, R.; Kumar, Harish; Afzal Ansari, M.; Sathik, N. P. M.; Ali, Rahbar; Kumar, Rakesh; Muralithar, S.; Singh, R. P.

2017-11-01

Spin distributions for several evaporation residues populated in the 16O+154Sm system have been measured at projectile energy ≈ 6.2 MeV/A by using the charged particle-γ-coincidence technique. The measured spin distributions of the evaporation residues populated through incomplete fusion associated with 'fast' α and 2α-emission channels are found to be entirely different from fusion-evaporation channels. It is observed that the mean input angular momentum for the evaporation residues formed in incomplete fusion channel is relatively higher than that observed for evaporation residues in complete fusion channels. The feeding intensity profile of evaporation residues populated through complete fusion and incomplete fusion have also been studied. The incomplete fusion channels are found to have narrow range feeding only for high spin states, while complete fusion channels are strongly fed over a broad spin range and widely populated. Comparison of present results with earlier data suggests that the mean input angular momentum values are relatively smaller for spherical target than that of deformed target using the same projectile and incident energy highlighting the role of target deformation in incomplete fusion dynamics.

Spin coherent states phenomena probed by quantum state tomography in Zeeman perturbed nuclear quadrupole resonance

NASA Astrophysics Data System (ADS)

Teles, João; Auccaise, Ruben; Rivera-Ascona, Christian; Araujo-Ferreira, Arthur G.; Andreeta, José P.; Bonagamba, Tito J.

2018-07-01

Recently, we reported an experimental implementation of quantum information processing (QIP) by nuclear quadrupole resonance (NQR). In this work, we present the first quantum state tomography (QST) experimental implementation in the NQR QIP context. Two approaches are proposed, employing coherence selection by temporal and spatial averaging. Conditions for reduction in the number of cycling steps are analyzed, which can be helpful for larger spin systems. The QST method was applied to the study of spin coherent states, where the alignment-to-orientation phenomenon and the evolution of squeezed spin states show the effect of the nonlinear quadrupole interaction intrinsic to the NQR system. The quantum operations were implemented using a single-crystal sample of KClO3 and observing ^{35}Cl nuclei, which posses spin 3/2.

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.

Nuclear-spin-independent short-range three-body physics in ultracold atoms.

PubMed

Gross, Noam; Shotan, Zav; Kokkelmans, Servaas; Khaykovich, Lev

2010-09-03

We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold 7Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross, Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.

Low- and high-spin excited states in 139Pr

NASA Astrophysics Data System (ADS)

Aryaeinejad, R.; McHarris, Wm. C.

1988-05-01

The level structure of the N=80 nucleus 139Pr has been studied in-beam by the 140Ce(p,2nγ)139Pr reaction using a 25-MeV p beam and by the 139La(α,4nγ)139Pr reaction using a 47-MeV α beam. γ-ray singles, γ-γ coincidence (prompt and delayed), and γ-ray angular distribution experiments were performed. We have assigned 41 γ rays deexciting 24 states in 139Pr from the (p,2nγ) reaction and 43 γ rays deexciting 31 (generally higher-spin) states from the (α,4nγ) reaction, for a total of 43 different states. These in-beam experiments, taken together with results from 139Ndm+g decay and the 141Pr(p,t)139Pr reaction, allowed Jπ assignments to be made for most of the states and allowed us to deduce the intrinsic configurations for many of them. These are discussed in terms of single-quasiparticle shell-model states and triaxial weak-coupled collective states and are compared with systematics for this nuclear region.

Electrical control of flying spin precession in chiral 1D edge states

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

Nakajima, Takashi; Komiyama, Susumu; Lin, Kuan-Ting

2013-12-04

Electrical control and detection of spin precession are experimentally demonstrated by using spin-resolved edge states in the integer quantum Hall regime. Spin precession is triggered at a corner of a biased metal gate, where electron orbital motion makes a sharp turn leading to a nonadiabatic change in the effective magnetic field via spin-orbit interaction. The phase of precession is controlled by the group velocity of edge-state electrons tuned by gate bias voltage: Spin-FET-like coherent control of spin precession is thus realized by all-electrical means.

A state interaction spin-orbit coupling density matrix renormalization group method

NASA Astrophysics Data System (ADS)

Sayfutyarova, Elvira R.; Chan, Garnet Kin-Lic

2016-06-01

We describe a state interaction spin-orbit (SISO) coupling method using density matrix renormalization group (DMRG) wavefunctions and the spin-orbit mean-field (SOMF) operator. We implement our DMRG-SISO scheme using a spin-adapted algorithm that computes transition density matrices between arbitrary matrix product states. To demonstrate the potential of the DMRG-SISO scheme we present accurate benchmark calculations for the zero-field splitting of the copper and gold atoms, comparing to earlier complete active space self-consistent-field and second-order complete active space perturbation theory results in the same basis. We also compute the effects of spin-orbit coupling on the spin-ladder of the iron-sulfur dimer complex [Fe2S2(SCH3)4]3-, determining the splitting of the lowest quartet and sextet states. We find that the magnitude of the zero-field splitting for the higher quartet and sextet states approaches a significant fraction of the Heisenberg exchange parameter.

A state interaction spin-orbit coupling density matrix renormalization group method

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

Sayfutyarova, Elvira R.; Chan, Garnet Kin-Lic

We describe a state interaction spin-orbit (SISO) coupling method using density matrix renormalization group (DMRG) wavefunctions and the spin-orbit mean-field (SOMF) operator. We implement our DMRG-SISO scheme using a spin-adapted algorithm that computes transition density matrices between arbitrary matrix product states. To demonstrate the potential of the DMRG-SISO scheme we present accurate benchmark calculations for the zero-field splitting of the copper and gold atoms, comparing to earlier complete active space self-consistent-field and second-order complete active space perturbation theory results in the same basis. We also compute the effects of spin-orbit coupling on the spin-ladder of the iron-sulfur dimer complex [Fe{submore » 2}S{sub 2}(SCH{sub 3}){sub 4}]{sup 3−}, determining the splitting of the lowest quartet and sextet states. We find that the magnitude of the zero-field splitting for the higher quartet and sextet states approaches a significant fraction of the Heisenberg exchange parameter.« less

Spin imbalance effect on the Larkin-Ovchinnikov-Fulde-Ferrel state

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

Yoshii, Ryosuke; Tsuchiya, Shunji; Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kanagawa 223-8521

2011-07-01

We study spin imbalance effects on the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) state relevant for superconductors under a strong magnetic field and spin polarized ultracold Fermi gas. We obtain the exact solution for the condensates with arbitrary spin imbalance and the fermion spectrum perturbatively in the presence of small spin imbalance. We also obtain fermion zero mode exactly without perturbation theory.

Spin-polarized ground state and exact quantization at ν=5/2

NASA Astrophysics Data System (ADS)

Pan, Wei

2002-03-01

The nature of the even-denominator fractional quantum Hall effect at ν=5/2 remains elusive, in particular, its ground state spin-polarization. An earlier, so-called "hollow core" model arrived at a spin-unpolarized wave function. The more recent calculations based on a model of BCS-like pairing of composite fermions, however, suggest that its ground state is spin-polarized. In this talk, I will first review the earlier experiments and then present our recent experimental results showing evidence for a spin-polarized state at ν=5/2. Our ultra-low temperature experiments on a high quality sample established the fully developed FQHE state at ν=5/2 as well as at ν=7/3 and 8/3, manifested by a vanishing R_xx and exact quantization of the Hall plateau. The tilted field experiments showed that the added in-plane magnetic fields not only destroyed the FQHE at ν=5/2, as seen before, but also induced an electrical anisotropy, which is now interpreted as a phase transition from a paired, spin-polarized ν=5/2 state to a stripe phase, not unlike the ones at ν=9/2, 11/2, etc in the N > 1 higher Landau levels. Furthermore, in the experiments on the heterojunction insulated-gate field-effect transistors (HIGFET) at dilution refrigerator temperatures, a strong R_xx minimum and a concomitant developing Hall plateau were observed at ν=5/2 in a magnetic field as high as 12.6 Tesla. This and the subsequent density dependent studies of its energy gap largely rule out a spin-singlet state and point quite convincingly towards a spin-polarized ground state at ν=5/2.

Unambiguously identifying spin states of transition-metal ions in the Earth (Invited)

NASA Astrophysics Data System (ADS)

Hsu, H.

2010-12-01

The spin state of a transition-metal ion in crystalline solids, defined by the number of unpaired electrons in the ion’s incomplete 3d shell, may vary with many factors, such as temperature, pressure, strain, and the local atomic configuration, to name a few. Such a phenomenon, known as spin-state crossover, plays a crucial role in spintronic materials. Recently, the pressure-induced spin-state crossover in iron-bearing minerals has been recognized to affect the minerals’ structural and elastic properties. However, the detailed mechanism of such crossover in iron-bearing magnesium silicate perovskite, the most abundant mineral in the Earth, remains unclear. A significant part of this confusion arises from the difficulty in reliably extracting the spin state from experiments. For the same reason, the thermally-induced spin-state crossover in lanthanum cobaltite (LaCoO3) has been controversial for more than four decades. In this talk, I will discuss how first-principle calculations can help clarifying these long-standing controversies. In addition to the total energy, equation of state, and elastic properties of each spin state, first-principle calculations also predict the electric field gradient (EFG) at the nucleus of each transition-metal ion. Our calculations showed that the nuclear EFG, a quantity that can be measured via Mössbauer or nuclear magnetic resonance (NMR) spectroscopy, depends primarily on the spin state, irrespective of the concentration or configuration of transition-metal ions. Such robustness makes EFG a unique fingerprint to identify the spin state. The combination of first-principle calculations and Mössbauer/NMR spectroscopy can therefore be a reliable and efficient approach in tackling spin-state crossover problems in the Earth. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The

Thermodynamics of Polaronic States in Artificial Spin Ice

NASA Astrophysics Data System (ADS)

Farhan, Alan

Artificial spin ices represent a class of systems consisting of lithographically patterned nanomagnets arranged in two-dimensional geometries. They were initially introduced as a two-dimensional analogue to geometrically frustrated pyrochlore spin ice, and the most recent introduction of artificial spin ice systems with thermally activated moment fluctuations not only delivered the possibility to directly investigate geometrical frustration and emergent phenomena with real space imaging, but also paved the way to design and investigate new two-dimensional magnetic metamaterials, where material properties can be directly manipulated giving rise to properties that do not exist in nature. Here, taking advantage of cryogenic photoemission electron microscopy, and using the concept of emergent magnetic charges, we are able to directly visualize the creation and annihilation of screened emergent magnetic monopole defects in artificial spin ice. We observe that these polaronic states arise as intermediate states, separating an energetically excited out-of-equilibrium state and low-energy equilibrium configurations. They appear as a result of a local screening effect between emergent magnetic charge defects and their neighboring magnetic charges, thus forming a transient minimum, before the system approaches a global minimum with the least amount of emergent magnetic charge defects. This project is funded by the Swiss National Science Foundation.

Spin polarization and magnetic dichroism in photoemission from core and valence states in localized magnetic systems. IV. Core-hole polarization in resonant photoemission

NASA Astrophysics Data System (ADS)

van der Laan, Gerrit; Thole, B. T.

1995-12-01

A simple theory is presented for core-hole polarization probed by resonant photoemission in a two-steps approximation. After excitation from a core level to the valence shell, the core hole decays into two shallower core holes under emission of an electron. The nonspherical core hole and the final state selected cause a specific angle and spin distribution of the emitted electron. The experiment is characterized by the ground-state moments, the polarization of the light, and the spin and angular distribution of the emitted electron. The intensity is a sum over ground-state expectation values of tensor operators times the probability to create a polarized core hole using polarized light, times the probability for decay of such a core hole into the final state. We give general expressions for the angle- and spin-dependent intensities in various regimes of Coulomb and spin-orbit interaction: LS, LSJ, and jjJ coupling. The core-polarization analysis, which generalizes the use of sum rules in x-ray absorption spectroscopy where the integrated peak intensities give ground-state expectation values of the spin and orbital moment operators, makes it possible to measure different linear combinations of these operators. As an application the 2p3/23p3p decay in ferromagnetic nickel is calculated using Hartree-Fock values for the radial matrix elements and phase factors, and compared with experiment, the dichroism is smaller in the 3P final state but stronger in the 1D, 1S peak.

Memory-built-in quantum cloning in a hybrid solid-state spin register

NASA Astrophysics Data System (ADS)

Wang, Weibin; Zu, Chong; He, Li; Zhang, Wengang; Duan, Luming

2015-05-01

As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude, and making it an ideal memory qubit. Our experiment is based on control of an individual nitrogen vacancy (NV) center in the diamond, which is a diamond defect that attracts strong interest in recent years with great potential for implementation of quantum information protocols.

Direct measurement of nonlocal entanglement of two-qubit spin quantum states.

PubMed

Cheng, Liu-Yong; Yang, Guo-Hui; Guo, Qi; Wang, Hong-Fu; Zhang, Shou

2016-01-18

We propose efficient schemes of direct concurrence measurement for two-qubit spin and photon-polarization entangled states via the interaction between single-photon pulses and nitrogen-vacancy (NV) centers in diamond embedded in optical microcavities. For different entangled-state types, diversified quantum devices and operations are designed accordingly. The initial unknown entangled states are possessed by two spatially separated participants, and nonlocal spin (polarization) entanglement can be measured with the aid of detection probabilities of photon (NV center) states. This non-demolition entanglement measurement manner makes initial entangled particle-pair avoid complete annihilation but evolve into corresponding maximally entangled states. Moreover, joint inter-qubit operation or global qubit readout is not required for the presented schemes and the final analyses inform favorable performance under the current parameters conditions in laboratory. The unique advantages of spin qubits assure our schemes wide potential applications in spin-based solid quantum information and computation.

Generalized concurrence measure for faithful quantification of multiparticle pure state entanglement using Lagrange's identity and wedge product

NASA Astrophysics Data System (ADS)

Bhaskara, Vineeth S.; Panigrahi, Prasanta K.

2017-05-01

Concurrence, introduced by Hill and Wootters (Phys Rev Lett 78:5022, 1997), provides an important measure of entanglement for a general pair of qubits that is faithful: strictly positive for entangled states and vanishing for all separable states. Such a measure captures the entire content of entanglement, providing necessary and sufficient conditions for separability. We present an extension of concurrence to multiparticle pure states in arbitrary dimensions by a new framework using the Lagrange's identity and wedge product representation of separability conditions, which coincides with the "I-concurrence" of Rungta et al. (Phys Rev A 64:042315, 2001) who proposed by extending Wootters's spin-flip operator to a so-called universal inverter superoperator. Our framework exposes an inherent geometry of entanglement and may be useful for the further extensions to mixed and continuous variable states.

Entangling distant solid-state spins via thermal phonons

NASA Astrophysics Data System (ADS)

Cao, Puhao; Betzholz, Ralf; Zhang, Shaoliang; Cai, Jianming

2017-12-01

The implementation of quantum entangling gates between qubits is essential to achieve scalable quantum computation. Here, we propose a robust scheme to realize an entangling gate for distant solid-state spins via a mechanical oscillator in its thermal equilibrium state. By appropriate Hamiltonian engineering and usage of a protected subspace, we show that the proposed scheme is able to significantly reduce the thermal effect of the mechanical oscillator on the spins. In particular, we demonstrate that a high entangling gate fidelity can be achieved even for a relatively high thermal occupation. Our scheme can thus relax the requirement for ground-state cooling of the mechanical oscillator, and may find applications in scalable quantum information processing in hybrid solid-state architectures.

Fuel Distribution Estimate via Spin Period to Precession Period Ratio for the Advanced Composition Explorer

NASA Technical Reports Server (NTRS)

DeHart, Russell; Smith, Eric; Lakin, John

2015-01-01

The spin period to precession period ratio of a non-axisymmetric spin-stabilized spacecraft, the Advanced Composition Explorer (ACE), was used to estimate the remaining mass and distribution of fuel within its propulsion system. This analysis was undertaken once telemetry suggested that two of the four fuel tanks had no propellant remaining, contrary to pre-launch expectations of the propulsion system performance. Numerical integration of possible fuel distributions was used to calculate moments of inertia for the spinning spacecraft. A Fast Fourier Transform (FFT) of output from a dynamics simulation was employed to relate calculated moments of inertia to spin and precession periods. The resulting modeled ratios were compared to the actual spin period to precession period ratio derived from the effect of post-maneuver nutation angle on sun sensor measurements. A Monte Carlo search was performed to tune free parameters using the observed spin period to precession period ratio over the life of the mission. This novel analysis of spin and precession periods indicates that at the time of launch, propellant was distributed unevenly between the two pairs of fuel tanks, with one pair having approximately 20% more propellant than the other pair. Furthermore, it indicates the pair of the tanks with less fuel expelled all of its propellant by 2014 and that approximately 46 kg of propellant remains in the other two tanks, an amount that closely matches the operational fuel accounting estimate. Keywords: Fuel Distribution, Moments of Inertia, Precession, Spin, Nutation

The role of the F spin-orbit excited state in the F+H(2) and F+HD reactions

NASA Astrophysics Data System (ADS)

Tzeng, Yi-Ren

In this dissertation we study the role of the F spin-orbit excited state (F*) in the F + H2 and F + HD reactions using quantum mechanical calculations. The calculations involve multiple potential energy surfaces (the Alexander-Stark-Werner, or ASW, PESs), and include an accurate treatment of the couplings (non-adiabatic, spin-orbit, and Coriolis) among all three electronic states. For the F + H2 reaction, we calculate the center-of-mass differential cross sections and laboratory-frame angular distributions at the four different combinations of collision energies and hydrogen isotopomer investigated in the experiments of Neumark et al. [J. Chem. Phys., 82, 3045 (1985)]. Comparisons with the calculations on the Stark-Werner (SW) and Hartke-Stark-Werner (HSW) PESs, which are limited to the lowest electronically adiabatic state, show that non-adiabatic couplings greatly reduce backward scattering. Surprisingly, we find the shapes of both the CM DCSs and LAB ADs are insensitive to the fraction of F* presented in the F beam. For the F + HD reaction, we calculate the excitation functions and product translational energy distribution functions to study the reactivity of F*. Comparisons with the experiment by Liu and co-workers [J. Chem. Phys., 113, 3633 (2000)] confirm the relatively low reactivity of spin-orbit excited state (F*) atoms. Excellent agreement with the experiment is obtained under the assumption that the F*:F concentration ratio equals 0.16:0.84 in the molecular beam, which corresponds to a thermal equilibrium of the two spin-orbit states at the experimental temperature (600K). From the accurate calculation of the F* reactivity and its relatively small contribution to the overall reactivity of the reaction, we attribute discrepancies between calculation and experiment to an inadequacy in the simulation of the reactivity of the F ground state, likely a result of the residual errors in the ground electronic potential energy surface.

Selective Equilibration of Spin-Polarized Quantum Hall Edge States in Graphene

NASA Astrophysics Data System (ADS)

Amet, F.; Williams, J. R.; Watanabe, K.; Taniguchi, T.; Goldhaber-Gordon, D.

2014-05-01

We report on transport measurements of dual-gated, single-layer graphene devices in the quantum Hall regime, allowing for independent control of the filling factors in adjoining regions. Progress in device quality allows us to study scattering between edge states when the fourfold degeneracy of the Landau level is lifted by electron correlations, causing edge states to be spin and/or valley polarized. In this new regime, we observe a dramatic departure from the equilibration seen in more disordered devices: edge states with opposite spins propagate without mixing. As a result, the degree of equilibration inferred from transport can reveal the spin polarization of the ground state at each filling factor. In particular, the first Landau level is shown to be spin polarized at half filling, providing an independent confirmation of a conclusion of Young et al. [Nat. Phys. 8, 550 (2012)]. The conductance in the bipolar regime is strongly suppressed, indicating that copropagating edge states, even with the same spin, do not equilibrate along PN interfaces. We attribute this behavior to the formation of an insulating ν =0 stripe at the PN interface.

Probing the degenerate states of V-point singularities.

PubMed

Ram, B S Bhargava; Sharma, Anurag; Senthilkumaran, Paramasivam

2017-09-15

V-points are polarization singularities in spatially varying linearly polarized optical fields and are characterized by the Poincare-Hopf index η. Each V-point singularity is a superposition of two oppositely signed orbital angular momentum states in two orthogonal spin angular momentum states. Hence, a V-point singularity has zero net angular momentum. V-points with given |η| have the same (amplitude) intensity distribution but have four degenerate polarization distributions. Each of these four degenerate states also produce identical diffraction patterns. Hence to distinguish these degenerate states experimentally, we present in this Letter a method involving a combination of polarization transformation and diffraction. This method also shows the possibility of using polarization singularities in place of phase singularities in optical communication and quantum information processing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f>1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f >1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

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

Thermodynamic properties of Fermi gases in states with defined many-body spins

NASA Astrophysics Data System (ADS)

Yurovsky, Vladimir

2016-05-01

Zero-range interactions in cold spin- 1 / 2 Fermi gases can be described by single interaction strength, since collisions of atoms in the same spin state are forbidden by the Pauli principle. In a spin-independent trap potential (even in the presence of a homogeneous spin-dependent external field), the gas can persist in a state with the given many-body spin, since the spin operator commutes with the Hamiltonian. Spin and spatial degrees of freedom in such systems are separated, and the spin and spatial wavefunctions form non-Abelian irreducible representations of the symmetric group, unless the total spin is S = N / 2 for N atoms (see). Although the total wavefunction, being a linear combination of products of the spin and spatial functions, is permutation-antisymmetric, the non-Abelian permutation symmetry is disclosed in the matrix elements and, as demonstrated here, in thermodynamic properties. The effects include modification of the specific heat and compressibility of the gas.

Observation of the spin-polarized surface state in a noncentrosymmetric superconductor BiPd

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

Neupane, Madhab; Alidoust, Nasser; Hosen, M. Mofazzel

Recently, noncentrosymmetric superconductor BiPd has attracted considerable research interest due to the possibility of hosting topological superconductivity. Here in this paper we report a systematic high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES study of the normal state electronic and spin properties of BiPd. Our experimental results show the presence of a surface state at higher-binding energy with the location of Dirac point at around 700 meV below the Fermi level. The detailed photon energy, temperature-dependent and spin-resolved ARPES measurements complemented by our first-principles calculations demonstrate the existence of the spin-polarized surface states at high-binding energy. The absence of suchmore » spin-polarized surface states near the Fermi level negates the possibility of a topological superconducting behaviour on the surface. Our direct experimental observation of spin-polarized surface states in BiPd provides critical information that will guide the future search for topological superconductivity in noncentrosymmetric materials.« less

Observation of the spin-polarized surface state in a noncentrosymmetric superconductor BiPd

DOE PAGES

Neupane, Madhab; Alidoust, Nasser; Hosen, M. Mofazzel; ...

2016-11-07

Recently, noncentrosymmetric superconductor BiPd has attracted considerable research interest due to the possibility of hosting topological superconductivity. Here in this paper we report a systematic high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES study of the normal state electronic and spin properties of BiPd. Our experimental results show the presence of a surface state at higher-binding energy with the location of Dirac point at around 700 meV below the Fermi level. The detailed photon energy, temperature-dependent and spin-resolved ARPES measurements complemented by our first-principles calculations demonstrate the existence of the spin-polarized surface states at high-binding energy. The absence of suchmore » spin-polarized surface states near the Fermi level negates the possibility of a topological superconducting behaviour on the surface. Our direct experimental observation of spin-polarized surface states in BiPd provides critical information that will guide the future search for topological superconductivity in noncentrosymmetric materials.« less

Topological winding properties of spin edge states in the Kane-Mele graphene model

NASA Astrophysics Data System (ADS)

Wang, Zhigang; Hao, Ningning; Zhang, Ping

2009-09-01

We study the spin edge states in the quantum spin-Hall (QSH) effect on a single-atomic layer graphene-ribbon system with both intrinsic and Rashba spin-orbit couplings. The Harper equation for solving the energies of the spin edge states is derived. The results show that in the QSH phase, there are always two pairs of gapless spin-filtered edge states in the bulk energy gap, corresponding to two pairs of zero points of the Bloch function on the complex-energy Riemann surface (RS). The topological aspect of the QSH phase can be distinguished by the difference of the winding numbers of the spin edge states with different polarized directions cross the holes of the RS, which is equivalent to the Z2 topological invariance proposed by Kane and Mele [Phys. Rev. Lett. 95, 146802 (2005)].

EPR oximetry in three spatial dimensions using sparse spin distribution

NASA Astrophysics Data System (ADS)

Som, Subhojit; Potter, Lee C.; Ahmad, Rizwan; Vikram, Deepti S.; Kuppusamy, Periannan

2008-08-01

A method is presented to use continuous wave electron paramagnetic resonance imaging for rapid measurement of oxygen partial pressure in three spatial dimensions. A particulate paramagnetic probe is employed to create a sparse distribution of spins in a volume of interest. Information encoding location and spectral linewidth is collected by varying the spatial orientation and strength of an applied magnetic gradient field. Data processing exploits the spatial sparseness of spins to detect voxels with nonzero spin and to estimate the spectral linewidth for those voxels. The parsimonious representation of spin locations and linewidths permits an order of magnitude reduction in data acquisition time, compared to four-dimensional tomographic reconstruction using traditional spectral-spatial imaging. The proposed oximetry method is experimentally demonstrated for a lithium octa- n-butoxy naphthalocyanine (LiNc-BuO) probe using an L-band EPR spectrometer.

Generating spin squeezing states and Greenberger-Horne-Zeilinger entanglement using a hybrid phonon-spin ensemble in diamond

NASA Astrophysics Data System (ADS)

Xia, Keyu; Twamley, Jason

2016-11-01

Quantum squeezing and entanglement of spins can be used to improve the sensitivity in quantum metrology. Here we propose a scheme to create collective coupling of an ensemble of spins to a mechanical vibrational mode actuated by an external magnetic field. We find an evolution time where the mechanical motion decouples from the spins, and the accumulated geometric phase yields a squeezing of 5.9 dB for 20 spins. We also show the creation of a Greenberger-Horne-Zeilinger spin state for 20 spins with a fidelity of ˜0.62 at cryogenic temperature. The numerical simulations show that the geometric-phase-based scheme is mostly immune to thermal mechanical noise.

Low-Spin States From Decay Studies in the Mass 80 Region

PubMed Central

Döring, J.; Aprahamian, A.; Wiescher, M.

2000-01-01

Neutron-deficient nuclei in the mass 80 region are known to exhibit strongly deformed ground states deduced mainly from yrast-state properties measured in-beam via heavy-ion fusion-evaporation reactions. Vibrational excitations and non-yrast states as well as their interplay with the observed rotational collectivity have been less studied to date within this mass region. Thus, several β-decay experiments have been performed to populate low-spin states in the neutron-deficient 80,84Y and 80,84Sr nuclei. An overview of excited 0+ states in Sr and Kr nuclei is given and conclusions about shape evolution at low-spins are presented. In general, the non-yrast states in even-even Sr nuclei show mainly vibration-like collectivity which evolves to rotational behavior with increasing spin and decreasing neutron number. PMID:27551586

Spin State Control of the Perovskite Rh/Co Oxides

PubMed Central

Terasaki, Ichiro; Shibasaki, Soichiro; Yoshida, Shin; Kobayashi, Wataru

2010-01-01

We show why and how the spin state of transition-metal ions affects the thermoelectric properties of transition-metal oxides by investigating two perovskite-related oxides. In the A-site ordered cobalt oxide Sr3YCo4O10.5, partial substitution of Ca for Sr acts as chemical pressure, which compresses the unit cell volume to drive the spin state crossover, and concomitantly changes the magnetization and thermopower. In the perovskite rhodium oxide LaRhO3, partial substitution of Sr for La acts as hole-doping, and the resistivity and thermopower decrease systematically with the Sr concentration. The thermopower remains large values at high temperatures (>150 μV/K at 800 K), which makes a remarkable contrast to La1−xSrxCoO3. We associate this with the stability of the low spin state of the Rh3+ ions.

Creating Spin-One Fermions in the Presence of Artificial Spin-Orbit Fields: Emergent Spinor Physics and Spectroscopic Properties

NASA Astrophysics Data System (ADS)

Kurkcuoglu, Doga Murat; de Melo, C. A. R. Sá

2018-05-01

We propose the creation and investigation of a system of spin-one fermions in the presence of artificial spin-orbit coupling, via the interaction of three hyperfine states of fermionic atoms to Raman laser fields. We explore the emergence of spinor physics in the Hamiltonian described by the interaction between light and atoms, and analyze spectroscopic properties such as dispersion relation, Fermi surfaces, spectral functions, spin-dependent momentum distributions and density of states. Connections to spin-one bosons and SU(3) systems is made, as well relations to the Lifshitz transition and Pomeranchuk instability are presented.

Quantum entanglement and spin control in silicon nanocrystal.

PubMed

Berec, Vesna

2012-01-01

Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure (29)Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of (29)Si <100> axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm) to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of (29)Si. Quantum discretization of density of states (DOS) was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD) and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution.PACS NUMBERS: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj.

Spin-state blockade in Te6+-substituted electron-doped LaCoO3

NASA Astrophysics Data System (ADS)

Tomiyasu, Keisuke; Koyama, Shun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi

2015-03-01

Perovskite-type LaCoO3 (Co3+: d6) is a rare inorganic material with sensitive and characteristic responses among low, intermediate, and high spin states. For example, in insulating nonmagnetic low-spin states below about 20 K, light hole doping (Ni substitution) induces much larger magnetization than expected; over net 10μB/hole (5μB/Ni) for 1μB/hole (1μB/Ni), in which the nearly isolated dopants locally change the surrounding Co low-spin states to magnetic ones and form spin molecules with larger total spin. Further, the former is isotropic, whereas the latter exhibits characteristic anisotropy probably because of Jahn-Teller distortion. In contrast, for electron doping, relatively insensitive spin-state responses were reported, as in LaCo(Ti4+) O3, but are not clarified, and are somewhat controversial. Here, we present macroscopic measurement data of another electron-doped system LaCo(Te6+) O3 and discuss the spin-state responses. This study was financially supported by Grants-in-Aid for Young Scientists (B) (No. 22740209 and 26800174) from the MEXT of Japan.

Matrix product states for su(2) invariant quantum spin chains

NASA Astrophysics Data System (ADS)

Zadourian, Rubina; Fledderjohann, Andreas; Klümper, Andreas

2016-08-01

A systematic and compact treatment of arbitrary su(2) invariant spin-s quantum chains with nearest-neighbour interactions is presented. The ground-state is derived in terms of matrix product states (MPS). The fundamental MPS calculations consist of taking products of basic tensors of rank 3 and contractions thereof. The algebraic su(2) calculations are carried out completely by making use of Wigner calculus. As an example of application, the spin-1 bilinear-biquadratic quantum chain is investigated. Various physical quantities are calculated with high numerical accuracy of up to 8 digits. We obtain explicit results for the ground-state energy, entanglement entropy, singlet operator correlations and the string order parameter. We find an interesting crossover phenomenon in the correlation lengths.

Optical charge state control of spin defects in 4H-SiC

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

Wolfowicz, Gary; Anderson, Christopher P.; Yeats, Andrew L.

Defects in silicon carbide (SiC) have emerged as a favorable platform for optically active spin-based quantum technologies. Spin qubits exist in specific charge states of these defects, where the ability to control these states can provide enhanced spin-dependent readout and long-term charge stability. We investigate this charge state control for two major spin qubits in 4H-SiC, the divacancy and silicon vacancy, obtaining bidirectional optical charge conversion between the bright and dark states of these defects. We measure increased photoluminescence from divacancy ensembles by up to three orders of magnitude using near-ultraviolet excitation, depending on the substrate, and without degrading themore » electron spin coherence time. This charge conversion remains stable for hours at cryogenic temperatures, allowing spatial and persistent patterning of the charge state populations. As a result, we develop a comprehensive model of the defects and optical processes involved, offering a strong basis to improve material design and to develop quantum applications in SiC.« less

Optical charge state control of spin defects in 4H-SiC

DOE PAGES

Wolfowicz, Gary; Anderson, Christopher P.; Yeats, Andrew L.; ...

2017-11-30

Defects in silicon carbide (SiC) have emerged as a favorable platform for optically active spin-based quantum technologies. Spin qubits exist in specific charge states of these defects, where the ability to control these states can provide enhanced spin-dependent readout and long-term charge stability. We investigate this charge state control for two major spin qubits in 4H-SiC, the divacancy and silicon vacancy, obtaining bidirectional optical charge conversion between the bright and dark states of these defects. We measure increased photoluminescence from divacancy ensembles by up to three orders of magnitude using near-ultraviolet excitation, depending on the substrate, and without degrading themore » electron spin coherence time. This charge conversion remains stable for hours at cryogenic temperatures, allowing spatial and persistent patterning of the charge state populations. As a result, we develop a comprehensive model of the defects and optical processes involved, offering a strong basis to improve material design and to develop quantum applications in SiC.« less

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.

Spin-squeezing and Dicke-state preparation by heterodyne measurement

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

Vanderbruggen, T.; Bernon, S.; Bertoldi, A.

2011-01-15

We investigate the quantum nondemolition (QND) measurement of an atomic population based on a heterodyne detection and show that the induced back-action allows for the preparation of both spin-squeezed and Dicke states. We use a wave-vector formalism to describe the stochastic process of the measurement and the associated atomic evolution. Analytical formulas of the atomic distribution momenta are derived in the weak-coupling regime both for short- and long-time behavior, and they are in good agreement with those obtained by a Monte Carlo simulation. The experimental implementation of the proposed heterodyne detection scheme is discussed. The role played in the squeezingmore » process by the spontaneous emission is considered.« less

Polar-Core Spin Vortex of Quasi-2D Spin-2 Condensate in a Flat-Bottomed Optical Trap

NASA Astrophysics Data System (ADS)

Zheng, Gong-Ping; Chang, Gao-Zhan; Li, Pin; Li, Ting

2017-10-01

Motivated by the recent experiments realized in a flat-bottomed optical trap [Science 347 (2015) 167; Nat. Commun. 6 (2015) 6162], we study the ground state of polar-core spin vortex of quasi-2D spin-2 condensate in a homogeneous trap plus a weak magnetic field. The exact spatial distribution of local spin is obtained and the vortex core are observed to decrease with the growth of the effective spin-spin interaction. For the larger effective spin-spin interaction, the spatial distribution of spin magnitude in spin-2 condensate we obtained agrees well with that of spin-1 condensate in a homogeneous trap, where a polar-core spin vortex was schematically demonstrated as a fully-magnetized planar spin texture with a zero-spin core. The effective spin-spin interaction is proportional to both the bare spin-spin interaction and the radius of the homogeneous trap, simultaneously. Thus the polar-core spin vortex we obtained can be easily controlled by the radius of the trap. Supported by the National Natural Science Foundation of China under Grant No. 11274095, the Key Scientific Research Project of Henan Province of China under Grant No. 16A140011, and the High Performance Computing Center of Henan Normal University

On the structure and spin states of Fe(III)-EDDHA complexes.

PubMed

Gómez-Gallego, Mar; Fernández, Israel; Pellico, Daniel; Gutiérrez, Angel; Sierra, Miguel A; Lucena, Juan J

2006-07-10

DFT methods are suitable for predicting both the geometries and spin states of EDDHA-Fe(III) complexes. Thus, extensive DFT computational studies have shown that the racemic-Fe(III) EDDHA complex is more stable than the meso isomer, regardless of the spin state of the central iron atom. A comparison of the energy values obtained for the complexes under study has also shown that high-spin (S = 5/2) complexes are more stable than low-spin (S = 1/2) ones. These computational results matched the experimental results of the magnetic susceptibility values of both isomers. In both cases, their behavior has been fitted as being due to isolated high-spin Fe(III) in a distorted octahedral environment. The study of the correlation diagram also confirms the high-spin iron in complex 2b. The geometry optimization of these complexes performed with the standard 3-21G* basis set for hydrogen, carbon, oxygen, and nitrogen and the Hay-Wadt small-core effective core potential (ECP) including a double-xi valence basis set for iron, followed by single-point energy refinement with the 6-31G* basis set, is suitable for predicting both the geometries and the spin-states of EDDHA-Fe(III) complexes. The presence of a high-spin iron in Fe(III)-EDDHA complexes could be the key to understanding their lack of reactivity in electron-transfer processes, either chemically or electrochemically induced, and their resistance to photodegradation.

High-fidelity projective read-out of a solid-state spin quantum register.

PubMed

Robledo, Lucio; Childress, Lilian; Bernien, Hannes; Hensen, Bas; Alkemade, Paul F A; Hanson, Ronald

2011-09-21

Initialization and read-out of coupled quantum systems are essential ingredients for the implementation of quantum algorithms. Single-shot read-out of the state of a multi-quantum-bit (multi-qubit) register would allow direct investigation of quantum correlations (entanglement), and would give access to further key resources such as quantum error correction and deterministic quantum teleportation. Although spins in solids are attractive candidates for scalable quantum information processing, their single-shot detection has been achieved only for isolated qubits. Here we demonstrate the preparation and measurement of a multi-spin quantum register in a low-temperature solid-state system by implementing resonant optical excitation techniques originally developed in atomic physics. We achieve high-fidelity read-out of the electronic spin associated with a single nitrogen-vacancy centre in diamond, and use this read-out to project up to three nearby nuclear spin qubits onto a well-defined state. Conversely, we can distinguish the state of the nuclear spins in a single shot by mapping it onto, and subsequently measuring, the electronic spin. Finally, we show compatibility with qubit control: we demonstrate initialization, coherent manipulation and single-shot read-out in a single experiment on a two-qubit register, using techniques suitable for extension to larger registers. These results pave the way for a test of Bell's inequalities on solid-state spins and the implementation of measurement-based quantum information protocols. © 2011 Macmillan Publishers Limited. All rights reserved

Solid-state electron spin lifetime limited by phononic vacuum modes.

PubMed

Astner, T; Gugler, J; Angerer, A; Wald, S; Putz, S; Mauser, N J; Trupke, M; Sumiya, H; Onoda, S; Isoya, J; Schmiedmayer, J; Mohn, P; Majer, J

2018-04-01

Longitudinal relaxation is the process by which an excited spin ensemble decays into its thermal equilibrium with the environment. In solid-state spin systems, relaxation into the phonon bath usually dominates over the coupling to the electromagnetic vacuum 1-9 . In the quantum limit, the spin lifetime is determined by phononic vacuum fluctuations 10 . However, this limit was not observed in previous studies due to thermal phonon contributions 11-13 or phonon-bottleneck processes 10, 14,15 . Here we use a dispersive detection scheme 16,17 based on cavity quantum electrodynamics 18-21 to observe this quantum limit of spin relaxation of the negatively charged nitrogen vacancy (NV - ) centre 22 in diamond. Diamond possesses high thermal conductivity even at low temperatures 23 , which eliminates phonon-bottleneck processes. We observe exceptionally long longitudinal relaxation times T 1 of up to 8 h. To understand the fundamental mechanism of spin-phonon coupling in this system we develop a theoretical model and calculate the relaxation time ab initio. The calculations confirm that the low phononic density of states at the NV - transition frequency enables the spin polarization to survive over macroscopic timescales.

Universal scheme for finite-probability perfect transfer of arbitrary multispin states through spin chains

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

Man, Zhong-Xiao, E-mail: zxman@mail.qfnu.edu.cn; An, Nguyen Ba, E-mail: nban@iop.vast.ac.vn; Xia, Yun-Jie, E-mail: yjxia@mail.qfnu.edu.cn

In combination with the theories of open system and quantum recovering measurement, we propose a quantum state transfer scheme using spin chains by performing two sequential operations: a projective measurement on the spins of ‘environment’ followed by suitably designed quantum recovering measurements on the spins of interest. The scheme allows perfect transfer of arbitrary multispin states through multiple parallel spin chains with finite probability. Our scheme is universal in the sense that it is state-independent and applicable to any model possessing spin–spin interactions. We also present possible methods to implement the required measurements taking into account the current experimental technologies.more » As applications, we consider two typical models for which the probabilities of perfect state transfer are found to be reasonably high at optimally chosen moments during the time evolution. - Highlights: • Scheme that can achieve perfect quantum state transfer is devised. • The scheme is state-independent and applicable to any spin-interaction models. • The scheme allows perfect transfer of arbitrary multispin states. • Applications to two typical models are considered in detail.« less

Opposite brain emotion-regulation patterns in identity states of dissociative identity disorder: a PET study and neurobiological model.

PubMed

Reinders, Antje A T S; Willemsen, Antoon T M; den Boer, Johan A; Vos, Herry P J; Veltman, Dick J; Loewenstein, Richard J

2014-09-30

Imaging studies in posttraumatic stress disorder (PTSD) have shown differing neural network patterns between hypo-aroused/dissociative and hyper-aroused subtypes. Since dissociative identity disorder (DID) involves different emotional states, this study tests whether DID fits aspects of the differing brain-activation patterns in PTSD. While brain activation was monitored using positron emission tomography, DID individuals (n=11) and matched DID-simulating healthy controls (n=16) underwent an autobiographic script-driven imagery paradigm in a hypo-aroused and a hyper-aroused identity state. Results were consistent with those previously found in the two PTSD subtypes for the rostral/dorsal anterior cingulate, the prefrontal cortex, and the amygdala and insula, respectively. Furthermore, the dissociative identity state uniquely activated the posterior association areas and the parahippocampal gyri, whereas the hyper-aroused identity state uniquely activated the caudate nucleus. Therefore, we proposed an extended PTSD-based neurobiological model for emotion modulation in DID: the hypo-aroused identity state activates the prefrontal cortex, cingulate, posterior association areas and parahippocampal gyri, thereby overmodulating emotion regulation; the hyper-aroused identity state activates the amygdala and insula as well as the dorsal striatum, thereby undermodulating emotion regulation. This confirms the notion that DID is related to PTSD as hypo-aroused and hyper-arousal states in DID and PTSD are similar. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Coherent manipulation of quantum spin states in a single molecular nanomagnet

NASA Astrophysics Data System (ADS)

Wernsdorfer, Wolfgang

The endeavour of quantum electronics is driven by one of the most ambitious technological goals of today's scientists: the realization of an operational quantum computer (http://qurope.eu). We started to address this goal by the new research field of molecular quantum spintronics. The building blocks are magnetic molecules, i.e. well-defined spin qubits. We will discuss this still largely unexplored field and present our first results: For example, using a molecular spin-transistor, we achieved the electronic read-out of the nuclear spin of an individual metal atom embedded in an SMM. We could show very long spin lifetimes (>10 s). Using the hyperfine Stark effect, which transforms electric fields into local effective magnetic fields, we could not only tune the resonance frequency by several MHz, but also perform coherent quantum manipulations on a single nuclear qubit faster than a μs by means of electrical fields only, establishing the individual addressability of identical nuclear qubits. Using three different microwave frequencies, we could implement a simple four-level Grover algorithm. S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science 344, 1135 (2014).

Cox's Chair Revisited: Can Spinning Alter Mood States?

PubMed

Winter, Lotta; Wollmer, M Axel; Laurens, Jean; Straumann, Dominik; Kruger, Tillmann H C

2013-01-01

Although there is clinical and historical evidence for a vivid relation between the vestibular and emotional systems, the neuroscientific underpinnings are poorly understood. The "spin doctors" of the nineteenth century used spinning chairs (e.g., Cox's chair) to treat conditions of mania or elevated arousal. On the basis of a recent study on a hexapod motion-simulator, in this prototypic investigation we explore the impact of yaw stimulation on a spinning chair on mood states. Using a controlled experimental stimulation paradigm on a unique 3-D-turntable at the University of Zurich we included 11 healthy subjects and assessed parameters of mood states and autonomic nervous system activity. The Multidimensional Mood State Questionnaire and Visual Analog Scales (VAS) were used to assess changes of mood in response to a 100 s yaw stimulation. In addition heart rate was continuously monitored during the experiment. Subjects indicated feeling less "good," "relaxed," "comfortable," and "calm" and reported an increased alertness after vestibular stimulation. However, there were no objective adverse effects of the stimulation. Accordingly, heart rate did not significantly differ in response to the stimulation. This is the first study in a highly controlled setting using the historical approach of stimulating the vestibular system to impact mood states. It demonstrates a specific interaction between the vestibular system and mood states and thereby supports recent experimental findings with a different stimulation technique. These results may inspire future research on the clinical potential of this method.

Ground-state phase diagram in the Kugel-Khomskii model with finite spin-orbit interactions

NASA Astrophysics Data System (ADS)

Koga, Akihisa; Nakauchi, Shiryu; Nasu, Joji

2018-05-01

We study ground-state properties in the Kugel-Khomskii model on the two-dimensional honeycomb lattice. Using the cluster mean-field approximations, we deal with the exchange and spin-orbit couplings on an equal footing. We then discuss the stability of the ferromagnetically ordered states against the nonmagnetic state, which is adiabatically connected to the quantum spin liquid state realized in a strong spin-orbit coupling limit.

Near-Earth asteroid satellite spins under spin-orbit coupling

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

Naidu, Shantanu P.; Margot, Jean-Luc

We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaoticmore » regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asychronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of light curve and radar observations.« less

Full Stark control of polariton states on a spin-orbit hypersphere

NASA Astrophysics Data System (ADS)

Li, Feng; Cancellieri, E.; Buonaiuto, G.; Skolnick, M. S.; Krizhanovskii, D. N.; Whittaker, D. M.

2016-11-01

The orbital angular momentum and the polarization of light are physical quantities widely investigated for classical and quantum information processing. In this work we propose to take advantage of strong light-matter coupling, circular-symmetric confinement, and transverse-electric transverse-magnetic splitting to exploit states where these two degrees of freedom are combined. To this end we develop a model based on a spin-orbit Poincaré hypersphere. Then we consider the example of semiconductor polariton systems and demonstrate full ultrafast Stark control of spin-orbit states. Moreover, by controlling states on three different spin-orbit spheres and switching from one sphere to another we demonstrate the control of different logic bits within one single physical system.

Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet

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

Fu, Mingxuan; Imai, Takahashi; Han, Tian -Heng

2015-11-06

Here, the kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu 3(OH) 6Cl 2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction.more » Combined with the magnetic field dependence of χ kagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.« less

Spin-lattice relaxation of individual solid-state spins

NASA Astrophysics Data System (ADS)

Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

2018-03-01

Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

Full-gap superconductivity in spin-polarised surface states of topological semimetal β-PdBi2.

PubMed

Iwaya, K; Kohsaka, Y; Okawa, K; Machida, T; Bahramy, M S; Hanaguri, T; Sasagawa, T

2017-10-17

A bulk superconductor possessing a topological surface state at the Fermi level is a promising system to realise long-sought topological superconductivity. Although several candidate materials have been proposed, experimental demonstrations concurrently exploring spin textures and superconductivity at the surface have remained elusive. Here we perform spectroscopic-imaging scanning tunnelling microscopy on the centrosymmetric superconductor β-PdBi 2 that hosts a topological surface state. By combining first-principles electronic-structure calculations and quasiparticle interference experiments, we determine the spin textures at the surface, and show not only the topological surface state but also all other surface bands exhibit spin polarisations parallel to the surface. We find that the superconducting gap fully opens in all the spin-polarised surface states. This behaviour is consistent with a possible spin-triplet order parameter expected for such in-plane spin textures, but the observed superconducting gap amplitude is comparable to that of the bulk, suggesting that the spin-singlet component is predominant in β-PdBi 2 .Although several materials have been proposed as topological superconductors, spin textures and superconductivity at the surface remain elusive. Here, Iwaya et al. determine the spin textures at the surface of a superconductor β-PdBi 2 and find the superconducting gap opening in all spin-polarised surface states.

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.

Finite-Momentum Dimer Bound State in Spin-Orbit Coupled Fermi Gas

NASA Astrophysics Data System (ADS)

Dong, Lin; Jiang, Lei; Hu, Hui; Pu, Han

2013-03-01

We investigate the two-body properties of a spin-1/2 Fermi gas subject to a spin-orbit coupling induced by laser fields. When attractive s-wave interaction between unlike spins is present, the system may form a dimer bound state. Surprisingly, under proper conditions, the bound state obtains finite center-of-mass momentum, whereas under the same condition but in the absence of the two-body interaction, the system has zero total momentum. This unusual result can be regarded as a consequence of the broken Galilean invariance by the spin-orbit coupling. Such a finite-momentum bound state will have profound effects on the many-body properties of the system. HP is supported by the NSF, the Welch Foundation (Grant No. C-1669), and DARPA. HH is supported by the ARC Discovery Projects (Grant No. DP0984522) and the National Basic Research Program of China (NFRP-China, Grant No. 2011CB921502).

A momentum-space formulation without partial wave decomposition for scattering of two spin-half particles

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

Fachruddin, Imam, E-mail: imam.fachruddin@sci.ui.ac.id; Salam, Agus

2016-03-11

A new momentum-space formulation for scattering of two spin-half particles, both either identical or unidentical, is formulated. As basis states the free linear-momentum states are not expanded into the angular-momentum states, the system’s spin states are described by the product of the spin states of the two particles, and the system’s isospin states by the total isospin states of the two particles. We evaluate the Lippmann-Schwinger equations for the T-matrix elements in these basis states. The azimuthal behavior of the potential and of the T-matrix elements leads to a set of coupled integral equations for the T-matrix elements in twomore » variables only, which are the magnitude of the relative momentum and the scattering angle. Some symmetry relations for the potential and the T-matrix elements reduce the number of the integral equations to be solved. A set of six spin operators to express any interaction of two spin-half particles is introduced. We show the spin-averaged differential cross section as being calculated in terms of the solution of the set of the integral equations.« less

Phenomenological study of decoherence in solid-state spin qubits due to nuclear spin diffusion

NASA Astrophysics Data System (ADS)

Biercuk, Michael J.; Bluhm, Hendrik

2011-06-01

We present a study of the prospects for coherence preservation in solid-state spin qubits using dynamical decoupling protocols. Recent experiments have provided the first demonstrations of multipulse dynamical decoupling sequences in this qubit system, but quantitative analyses of potential coherence improvements have been hampered by a lack of concrete knowledge of the relevant noise processes. We present calculations of qubit coherence under the application of arbitrary dynamical decoupling pulse sequences based on an experimentally validated semiclassical model. This phenomenological approach bundles the details of underlying noise processes into a single experimentally relevant noise power spectral density. Our results show that the dominant features of experimental measurements in a two-electron singlet-triplet spin qubit can be replicated using a 1/ω2 noise power spectrum associated with nuclear spin flips in the host material. Beginning with this validation, we address the effects of nuclear programming, high-frequency nuclear spin dynamics, and other high-frequency classical noise sources, with conjectures supported by physical arguments and microscopic calculations where relevant. Our results provide expected performance bounds and identify diagnostic metrics that can be measured experimentally in order to better elucidate the underlying nuclear spin dynamics.

Far-from-Equilibrium Field Theory of Many-Body Quantum Spin Systems: Prethermalization and Relaxation of Spin Spiral States in Three Dimensions

NASA Astrophysics Data System (ADS)

Babadi, Mehrtash; Demler, Eugene; Knap, Michael

2015-10-01

We study theoretically the far-from-equilibrium relaxation dynamics of spin spiral states in the three-dimensional isotropic Heisenberg model. The investigated problem serves as an archetype for understanding quantum dynamics of isolated many-body systems in the vicinity of a spontaneously broken continuous symmetry. We present a field-theoretical formalism that systematically improves on the mean field for describing the real-time quantum dynamics of generic spin-1 /2 systems. This is achieved by mapping spins to Majorana fermions followed by a 1 /N expansion of the resulting two-particle-irreducible effective action. Our analysis reveals rich fluctuation-induced relaxation dynamics in the unitary evolution of spin spiral states. In particular, we find the sudden appearance of long-lived prethermalized plateaus with diverging lifetimes as the spiral winding is tuned toward the thermodynamically stable ferro- or antiferromagnetic phases. The emerging prethermalized states are characterized by different bosonic modes being thermally populated at different effective temperatures and by a hierarchical relaxation process reminiscent of glassy systems. Spin-spin correlators found by solving the nonequilibrium Bethe-Salpeter equation provide further insight into the dynamic formation of correlations, the fate of unstable collective modes, and the emergence of fluctuation-dissipation relations. Our predictions can be verified experimentally using recent realizations of spin spiral states with ultracold atoms in a quantum gas microscope [S. Hild et al., Phys. Rev. Lett. 113, 147205 (2014), 10.1103/PhysRevLett.113.147205].

Role of entropy and structural parameters in the spin-state transition of LaCoO3

NASA Astrophysics Data System (ADS)

Chakrabarti, Bismayan; Birol, Turan; Haule, Kristjan

2017-11-01

The spin-state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge self-consistent density functional theory + embedded dynamical mean field theory (DFT+DMFT). We show from first principles that LaCoO3 cannot be described by a single, pure spin state at any temperature. Instead, we observe a gradual change in the population of higher-spin multiplets with increasing temperature, with the high-spin multiplets being excited at the onset of the spin-state transition followed by the intermediate-spin multiplets being excited at the metal-insulator-transition temperature. We explicitly elucidate the critical role of lattice expansion and oxygen octahedral rotations in the spin-state transition. We also reproduce, from first principles, that the spin-state transition and the metal-insulator transition in LaCoO3 occur at different temperature scales. In addition, our results shed light on the importance of electronic entropy in driving the spin-state transition, which has so far been ignored in all first-principles studies of this material.

Ground-state cooling of a carbon nanomechanical resonator by spin-polarized current.

PubMed

Stadler, P; Belzig, W; Rastelli, G

2014-07-25

We study the nonequilibrium steady state of a mechanical resonator in the quantum regime realized by a suspended carbon nanotube quantum dot in contact with two ferromagnets. Because of the spin-orbit interaction and/or an external magnetic field gradient, the spin on the dot couples directly to the flexural eigenmodes. Accordingly, the nanomechanical motion induces inelastic spin flips of the tunneling electrons. A spin-polarized current at finite bias voltage causes either heating or active cooling of the mechanical modes. We show that maximal cooling is achieved at resonant transport when the energy splitting between two dot levels of opposite spin equals the vibrational frequency. Even for weak electron-resonator coupling and moderate polarizations we can achieve ground-state cooling with a temperature of the leads, for instance, of T = 10 ω.

Distributed acoustic cues for caller identity in macaque vocalization.

PubMed

Fukushima, Makoto; Doyle, Alex M; Mullarkey, Matthew P; Mishkin, Mortimer; Averbeck, Bruno B

2015-12-01

Individual primates can be identified by the sound of their voice. Macaques have demonstrated an ability to discern conspecific identity from a harmonically structured 'coo' call. Voice recognition presumably requires the integrated perception of multiple acoustic features. However, it is unclear how this is achieved, given considerable variability across utterances. Specifically, the extent to which information about caller identity is distributed across multiple features remains elusive. We examined these issues by recording and analysing a large sample of calls from eight macaques. Single acoustic features, including fundamental frequency, duration and Weiner entropy, were informative but unreliable for the statistical classification of caller identity. A combination of multiple features, however, allowed for highly accurate caller identification. A regularized classifier that learned to identify callers from the modulation power spectrum of calls found that specific regions of spectral-temporal modulation were informative for caller identification. These ranges are related to acoustic features such as the call's fundamental frequency and FM sweep direction. We further found that the low-frequency spectrotemporal modulation component contained an indexical cue of the caller body size. Thus, cues for caller identity are distributed across identifiable spectrotemporal components corresponding to laryngeal and supralaryngeal components of vocalizations, and the integration of those cues can enable highly reliable caller identification. Our results demonstrate a clear acoustic basis by which individual macaque vocalizations can be recognized.

Distributed acoustic cues for caller identity in macaque vocalization

PubMed Central

Doyle, Alex M.; Mullarkey, Matthew P.; Mishkin, Mortimer; Averbeck, Bruno B.

2015-01-01

Individual primates can be identified by the sound of their voice. Macaques have demonstrated an ability to discern conspecific identity from a harmonically structured ‘coo’ call. Voice recognition presumably requires the integrated perception of multiple acoustic features. However, it is unclear how this is achieved, given considerable variability across utterances. Specifically, the extent to which information about caller identity is distributed across multiple features remains elusive. We examined these issues by recording and analysing a large sample of calls from eight macaques. Single acoustic features, including fundamental frequency, duration and Weiner entropy, were informative but unreliable for the statistical classification of caller identity. A combination of multiple features, however, allowed for highly accurate caller identification. A regularized classifier that learned to identify callers from the modulation power spectrum of calls found that specific regions of spectral–temporal modulation were informative for caller identification. These ranges are related to acoustic features such as the call’s fundamental frequency and FM sweep direction. We further found that the low-frequency spectrotemporal modulation component contained an indexical cue of the caller body size. Thus, cues for caller identity are distributed across identifiable spectrotemporal components corresponding to laryngeal and supralaryngeal components of vocalizations, and the integration of those cues can enable highly reliable caller identification. Our results demonstrate a clear acoustic basis by which individual macaque vocalizations can be recognized. PMID:27019727

Protocol for generating multiphoton entangled states from quantum dots in the presence of nuclear spin fluctuations

NASA Astrophysics Data System (ADS)

Denning, Emil V.; Iles-Smith, Jake; McCutcheon, Dara P. S.; Mork, Jesper

2017-12-01

Multiphoton entangled states are a crucial resource for many applications in quantum information science. Semiconductor quantum dots offer a promising route to generate such states by mediating photon-photon correlations via a confined electron spin, but dephasing caused by the host nuclear spin environment typically limits coherence (and hence entanglement) between photons to the spin T2* time of a few nanoseconds. We propose a protocol for the deterministic generation of multiphoton entangled states that is inherently robust against the dominating slow nuclear spin environment fluctuations, meaning that coherence and entanglement is instead limited only by the much longer spin T2 time of microseconds. Unlike previous protocols, the present scheme allows for the generation of very low error probability polarization encoded three-photon GHZ states and larger entangled states, without the need for spin echo or nuclear spin calming techniques.

State diagram of magnetostatic coupling phase-locked spin-torque oscillators

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

Zhang, Mengwei; Wang, Longze; Wei, Dan, E-mail: weidan@mail.tsinghua.edu.cn

2015-05-07

The state diagram of magnetostatic coupling phase-locked spin torque oscillator (STO) with perpendicular reference layer and planar field generation layer (FGL) is studied by the macrospin model and the micromagnetic model. The state diagrams of current densities are calculated under various external fields. The simulation shows that there are two phase-lock current density regions. In the phase-locked STOs in low current region I, the spin configuration of FGL is uniform; in high current region II, the spin configuration of FGL is highly nonuniform. In addition, the results with different STOs separation L{sub s} are compared, and the coupling between twomore » STOs is largely decreased when L{sub s} is increased from 40 nm to 60 nm.« less

Exact valence bond entanglement entropy and probability distribution in the XXX spin chain and the potts model.

PubMed

Jacobsen, J L; Saleur, H

2008-02-29

We determine exactly the probability distribution of the number N_(c) of valence bonds connecting a subsystem of length L>1 to the rest of the system in the ground state of the XXX antiferromagnetic spin chain. This provides, in particular, the asymptotic behavior of the valence-bond entanglement entropy S_(VB)=N_(c)ln2=4ln2/pi(2)lnL disproving a recent conjecture that this should be related with the von Neumann entropy, and thus equal to 1/3lnL. Our results generalize to the Q-state Potts model.

Complex-network description of thermal quantum states in the Ising spin chain

NASA Astrophysics Data System (ADS)

Sundar, Bhuvanesh; Valdez, Marc Andrew; Carr, Lincoln D.; Hazzard, Kaden R. A.

2018-05-01

We use network analysis to describe and characterize an archetypal quantum system—an Ising spin chain in a transverse magnetic field. We analyze weighted networks for this quantum system, with link weights given by various measures of spin-spin correlations such as the von Neumann and Rényi mutual information, concurrence, and negativity. We analytically calculate the spin-spin correlations in the system at an arbitrary temperature by mapping the Ising spin chain to fermions, as well as numerically calculate the correlations in the ground state using matrix product state methods, and then analyze the resulting networks using a variety of network measures. We demonstrate that the network measures show some traits of complex networks already in this spin chain, arguably the simplest quantum many-body system. The network measures give insight into the phase diagram not easily captured by more typical quantities, such as the order parameter or correlation length. For example, the network structure varies with transverse field and temperature, and the structure in the quantum critical fan is different from the ordered and disordered phases.

Determining titan's spin state from cassini radar images

USGS Publications Warehouse

Stiles, B.W.; Kirk, R.L.; Lorenz, R.D.; Hensley, S.; Lee, E.; Ostro, S.J.; Allison, M.D.; Callahan, P.S.; Gim, Y.; Iess, L.; Del Marmo, P.P.; Hamilton, G.; Johnson, W.T.K.; West, R.D.

2008-01-01

For some 19 areas of Titan's surface, the Cassini RADAR instrument has obtained synthetic aperture radar (SAR) images during two different flybys. The time interval between flybys varies from several weeks to two years. We have used the apparent misregistration (by 10-30 km) of features between separate flybys to construct a refined model of Titan's spin state, estimating six parameters: north pole right ascension and declination, spin rate, and these quantities' first time derivatives We determine a pole location with right ascension of 39.48 degrees and declination of 83.43 degrees corresponding to a 0.3 degree obliquity. We determine the spin rate to be 22.5781 deg day -1 or 0.001 deg day-1 faster than the synchronous spin rate. Our estimated corrections to the pole and spin rate exceed their corresponding standard errors by factors of 80 and 8, respectively. We also found that the rate of change in the pole right ascension is -30 deg century-1, ten times faster than right ascension rate of change for the orbit normal. The spin rate is increasing at a rate of 0.05 deg day -1 per century. We observed no significant change in pole declination over the period for which we have data. Applying our pole correction reduces the feature misregistration from tens of km to 3 km. Applying the spin rate and derivative corrections further reduces the misregistration to 1.2 km. ?? 2008. The American Astronomical Society. All rights reserved.

Theoretical study of dynamic electron-spin-polarization via the doublet-quartet quantum-mixed state and time-resolved ESR spectra of the quartet high-spin state.

PubMed

Teki, Yoshio; Matsumoto, Takafumi

2011-04-07

The mechanism of the unique dynamic electron polarization of the quartet (S = 3/2) high-spin state via a doublet-quartet quantum-mixed state and detail theoretical calculations of the population transfer are reported. By the photo-induced electron transfer, the quantum-mixed charge-separate state is generated in acceptor-donor-radical triad (A-D-R). This mechanism explains well the unique dynamic electron polarization of the quartet state of A-D-R. The generation of the selectively populated quantum-mixed state and its transfer to the strongly coupled pure quartet and doublet states have been treated both by a perturbation approach and by exact numerical calculations. The analytical solutions show that generation of the quantum-mixed states with the selective populations after de-coherence and/or accompanying the (complete) dephasing during the charge-recombination are essential for the unique dynamic electron polarization. Thus, the elimination of the quantum coherence (loss of the quantum information) is the key process for the population transfer from the quantum-mixed state to the quartet state. The generation of high-field polarization on the strongly coupled quartet state by the charge-recombination process can be explained by a polarization transfer from the quantum-mixed charge-separate state. Typical time-resolved ESR patterns of the quantum-mixed state and of the strongly coupled quartet state are simulated based on the generation mechanism of the dynamic electron polarization. The dependence of the spectral pattern of the quartet high-spin state has been clarified for the fine-structure tensor and the exchange interaction of the quantum-mixed state. The spectral pattern of the quartet state is not sensitive towards the fine-structure tensor of the quantum-mixed state, because this tensor contributes only as a perturbation in the population transfer to the spin-sublevels of the quartet state. Based on the stochastic Liouville equation, it is also

Asteroid (367943) 2012 DA14 Flyby Spin State Analysis

NASA Astrophysics Data System (ADS)

Benson, Conor; Scheeres, Daniel J.; Moskovitz, Nicholas

2017-10-01

On February 15, 2013 asteroid 2012 DA14 experienced an extremely close Earth encounter, passing within 27700 km altitude. This flyby gave observers the chance to directly detect flyby-induced changes to the asteroid’s spin state and physical properties. The strongest shape and spin state constraints were provided by Goldstone delay-Doppler radar and visible-wavelength photometry taken after closest approach. These data indicated a roughly 40 m x 20 m object in non-principal axis rotation. NPA states are described by two fundamental periods. Pφ is the average precession period of the long/short axis about the angular momentum vector and Pψ is the rotation period about the long/short axis.WindowCLEAN (Belton & Gandhi 1988) power spectrum analysis of the post flyby light curve showed three prominent frequencies, two of which were 1:2 multiples of each other. Mueller et al. (2002) suggest peaks with this relationship are 1/Pφ and 2/Pφ, implying that Pφ = 6.35 hr. Likely values for Pψ were then 8.72, 13.95, or 23.39 hr. These Pφ,Pψ pairs yielded six candidate spin states in total, one LAM and one SAM per pair.Second to fourth order, two-dimensional Fourier series fits to the light curve were best for periods of 6.359 and 8.724 hr. The two other candidate pairs were also in the top ten fits. Inertia constraints of a roughly 2:1 uniform density ellipsoid eliminated two of the three SAM states. Using JPL Horizons ephemerides and Lambertian ellipsoids, simulated light curves were generated. The simulated and observed power spectra were then compared for all angular momentum poles and reasonable ellipsoid elongations. Only the Pφ = 6.359 hr and Pψ = 8.724 hr LAM state produced light curves consistent with the observed frequency structure. All other states were clearly incompatible. With two well-fitting poles found, phasing the initial attitude and angular velocity yielded plausible matches to the observed light curve. Neglecting gravitational torques, neither

SU(2) slave-boson formulation of spin nematic states in S=(1)/(2) frustrated ferromagnets

NASA Astrophysics Data System (ADS)

Shindou, Ryuichi; Momoi, Tsutomu

2009-08-01

An SU(2) slave-boson formulation of bond-type spin nematic orders is developed in frustrated ferromagnets, where the spin nematic states are described as the resonating spin-triplet valence bond (RVB) states. The d vectors of spin-triplet pairing ansatzes play the role of the directors in the bond-type spin-quadrupolar states. The low-energy excitations around such spin-triplet RVB ansatzes generally comprise the (potentially massless) gauge bosons, massless Goldstone bosons, and spinon individual excitations. Extending the projective symmetry-group argument to the spin-triplet ansatzes, we show how to identify the number of massless gauge bosons efficiently. Applying this formulation, we next (i) enumerate possible mean-field solutions for the S=(1)/(2) ferromagnetic J1-J2 Heisenberg model on the square lattice, with ferromagnetic nearest neighbor J1 and competing antiferromagnetic next-nearest neighbor J2 and (ii) argue their stability against small gauge fluctuations. As a result, two stable spin-triplet RVB ansatzes are found in the intermediate coupling regime around J1:J2≃1:0.4 . One is the Z2 Balian-Werthamer (BW) state stabilized by the Higgs mechanism and the other is the SU(2) chiral p -wave (Anderson-Brinkman-Morel) state stabilized by the Chern-Simon mechanism. The former Z2 BW state in fact shows the same bond-type spin-quadrupolar order as found in the previous exact diagonalization study [Shannon , Phys. Rev. Lett. 96, 027213 (2006)].

Protecting solid-state spins from a strongly coupled environment

NASA Astrophysics Data System (ADS)

Chen, Mo; Calvin Sun, Won Kyu; Saha, Kasturi; Jaskula, Jean-Christophe; Cappellaro, Paola

2018-06-01

Quantum memories are critical for solid-state quantum computing devices and a good quantum memory requires both long storage time and fast read/write operations. A promising system is the nitrogen-vacancy (NV) center in diamond, where the NV electronic spin serves as the computing qubit and a nearby nuclear spin as the memory qubit. Previous works used remote, weakly coupled 13C nuclear spins, trading read/write speed for long storage time. Here we focus instead on the intrinsic strongly coupled 14N nuclear spin. We first quantitatively understand its decoherence mechanism, identifying as its source the electronic spin that acts as a quantum fluctuator. We then propose a scheme to protect the quantum memory from the fluctuating noise by applying dynamical decoupling on the environment itself. We demonstrate a factor of 3 enhancement of the storage time in a proof-of-principle experiment, showing the potential for a quantum memory that combines fast operation with long coherence time.

Fingerprint Recognition with Identical Twin Fingerprints

PubMed Central

Yang, Xin; Tian, Jie

2012-01-01

Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar. PMID:22558204

Fingerprint recognition with identical twin fingerprints.

PubMed

Tao, Xunqiang; Chen, Xinjian; Yang, Xin; Tian, Jie

2012-01-01

Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar.

Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

NASA Astrophysics Data System (ADS)

Gopinath, T.; Veglia, Gianluigi

2013-05-01

We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

PubMed

Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

2014-05-01

Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

Nuclear spin noise in the central spin model

NASA Astrophysics Data System (ADS)

Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail

2018-05-01

We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.

Manipulating topological states by imprinting non-collinear spin textures

DOE PAGES

Streubel, Robert; Han, Luyang; Im, Mi -Young; ...

2015-03-05

Topological magnetic states, such as chiral skyrmions, are of great scientific interest and show huge potential for novel spintronics applications, provided their topological charges can be fully controlled. So far skyrmionic textures have been observed in noncentrosymmetric crystalline materials with low symmetry and at low temperatures. We propose theoretically and demonstrate experimentally the design of spin textures with topological charge densities that can be tailored at ambient temperatures. Tuning the interlayer coupling in vertically stacked nanopatterned magnetic heterostructures, such as a model system of a Co/Pd multilayer coupled to Permalloy, the in-plane non-collinear spin texture of one layer can bemore » imprinted into the out-of-plane magnetised material. We observe distinct spin textures, e.g. vortices, magnetic swirls with tunable opening angle, donut states and skyrmion core configurations. We show that applying a small magnetic field, a reliable switching between topologically distinct textures can be achieved at remanence« less

A photonic link for donor spin qubits in silicon

NASA Astrophysics Data System (ADS)

Simmons, Stephanie

Atomically identical donor spin qubits in silicon offer excellent native quantum properties, which match or outperform many qubit rivals. To scale up such systems it would be advantageous to connect silicon donor spin qubits in a cavity-QED architecture. Many proposals in this direction introduce strong electric dipole interactions to the otherwise largely isolated spin qubit ground state in order to couple to superconducting cavities. Here I present an alternative approach, which uses the built-in strong electric dipole (optical) transitions of singly-ionized double donors in silicon. These donors, such as chalcogen donors S +, Se + and Te +, have the same ground-state spin Hamiltonians as shallow donors yet offer mid-gap binding energies and mid-IR optical access to excited orbital states. This photonic link is spin-selective which could be harnessed to measure and couple donor qubits using photonic cavity-QED. This approach should be robust to device environments with variable strains and electric fields, and will allow for CMOS- compatible, bulk-like, spatially separated donor qubit placement, optical parity measurements, and 4.2K operation. I will present preliminary data in support of this approach, including 4.2K optical initialization/readout in Earth's magnetic field, where long T1 and T2 times have been measured.

Non-identical multiplexing promotes chimera states

NASA Astrophysics Data System (ADS)

Ghosh, Saptarshi; Zakharova, Anna; Jalan, Sarika

2018-01-01

We present the emergence of chimeras, a state referring to coexistence of partly coherent, partly incoherent dynamics in networks of identical oscillators, in a multiplex network consisting of two non-identical layers which are interconnected. We demonstrate that the parameter range displaying the chimera state in the homogeneous first layer of the multiplex networks can be tuned by changing the link density or connection architecture of the same nodes in the second layer. We focus on the impact of the interconnected second layer on the enlargement or shrinking of the coupling regime for which chimeras are displayed in the homogeneous first layer. We find that a denser homogeneous second layer promotes chimera in a sparse first layer, where chimeras do not occur in isolation. Furthermore, while a dense connection density is required for the second layer if it is homogeneous, this is not true if the second layer is inhomogeneous. We demonstrate that a sparse inhomogeneous second layer which is common in real-world complex systems can promote chimera states in a sparse homogeneous first layer.

Iron monocyanide (FeCN): Spin-orbit and vibronic interactions in low-lying electronic states

NASA Astrophysics Data System (ADS)

Jerosimić, Stanka V.; Milovanović, Milan Z.

2018-04-01

The spin-orbit eigenvalues of low-energy quartet and sextet spatially degenerate electronic states of FeCN are reported, together with the combined effect of vibronic and spin-orbit interaction in the lowest-lying 14Δ and 16Δ states of FeCN, by using perturbational and variational method. Spin-orbit constants (ASO) have been calculated in the basis of: (a) two components of each degenerate state, (b) four components of 14Δ and 14Π (16Δ and 16Π) states, and (c) ten components of 16Δ, 16Π, 16Σ+, 14Δ, 14Π, and 14Σ+ states. The present calculations predict the values of ASO= -77 cm-1 for 16Δ and ASO= -108 cm-1 for 14Δ state in the lowest-energy spin-orbit manifolds of each state. The major perturbing state for the 14Δ state is the 14Π state (16Π for the sextet 16Δ). As expected, based on extremely small splitting and shallowness of the bending potential energy curves for the lowest-lying 4,6Δ states, the present study indicate that the vibronic coupling does not create significant splitting of the bending levels, but the influence of anharmonicity in the bending mode is more pronounced. However, the spin-orbit fine structure dominantly influences the spectra of this species.

Nonlocally sensing the magnetic states of nanoscale antiferromagnets with an atomic spin sensor

PubMed Central

Yan, Shichao; Malavolti, Luigi; Burgess, Jacob A. J.; Droghetti, Andrea; Rubio, Angel; Loth, Sebastian

2017-01-01

The ability to sense the magnetic state of individual magnetic nano-objects is a key capability for powerful applications ranging from readout of ultradense magnetic memory to the measurement of spins in complex structures with nanometer precision. Magnetic nano-objects require extremely sensitive sensors and detection methods. We create an atomic spin sensor consisting of three Fe atoms and show that it can detect nanoscale antiferromagnets through minute, surface-mediated magnetic interaction. Coupling, even to an object with no net spin and having vanishing dipolar stray field, modifies the transition matrix element between two spin states of the Fe atom–based spin sensor that changes the sensor’s spin relaxation time. The sensor can detect nanoscale antiferromagnets at up to a 3-nm distance and achieves an energy resolution of 10 μeV, surpassing the thermal limit of conventional scanning probe spectroscopy. This scheme permits simultaneous sensing of multiple antiferromagnets with a single-spin sensor integrated onto the surface. PMID:28560346

Topological Phases in Graphene Nanoribbons: Junction States, Spin Centers, and Quantum Spin Chains

NASA Astrophysics Data System (ADS)

Cao, Ting; Zhao, Fangzhou; Louie, Steven G.

2017-08-01

We show that semiconducting graphene nanoribbons (GNRs) of different width, edge, and end termination (synthesizable from molecular precursors with atomic precision) belong to different electronic topological classes. The topological phase of GNRs is protected by spatial symmetries and dictated by the terminating unit cell. We have derived explicit formulas for their topological invariants and shown that localized junction states developed between two GNRs of distinct topology may be tuned by lateral junction geometry. The topology of a GNR can be further modified by dopants, such as a periodic array of boron atoms. In a superlattice consisting of segments of doped and pristine GNRs, the junction states are stable spin centers, forming a Heisenberg antiferromagnetic spin 1 /2 chain with tunable exchange interaction. The discoveries here not only are of scientific interest for studies of quasi-one-dimensional systems, but also open a new path for design principles of future GNR-based devices through their topological characters.

Topological Phases in Graphene Nanoribbons: Junction States, Spin Centers, and Quantum Spin Chains.

PubMed

Cao, Ting; Zhao, Fangzhou; Louie, Steven G

2017-08-18

We show that semiconducting graphene nanoribbons (GNRs) of different width, edge, and end termination (synthesizable from molecular precursors with atomic precision) belong to different electronic topological classes. The topological phase of GNRs is protected by spatial symmetries and dictated by the terminating unit cell. We have derived explicit formulas for their topological invariants and shown that localized junction states developed between two GNRs of distinct topology may be tuned by lateral junction geometry. The topology of a GNR can be further modified by dopants, such as a periodic array of boron atoms. In a superlattice consisting of segments of doped and pristine GNRs, the junction states are stable spin centers, forming a Heisenberg antiferromagnetic spin 1/2 chain with tunable exchange interaction. The discoveries here not only are of scientific interest for studies of quasi-one-dimensional systems, but also open a new path for design principles of future GNR-based devices through their topological characters.

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.

Reexamination of relaxation of spins due to a magnetic field gradient: Identity of the Redfield and Torrey theories

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

Golub, R.; Rohm, Ryan M.; Swank, C. M.

2011-02-15

There is an extensive literature on magnetic-gradient-induced spin relaxation. Cates, Schaefer, and Happer, in a seminal publication, have solved the problem in the regime where diffusion theory (the Torrey equation) is applicable using an expansion of the density matrix in diffusion equation eigenfunctions and angular momentum tensors. McGregor has solved the problem in the same regime using a slightly more general formulation using the Redfield theory formulated in terms of the autocorrelation function of the fluctuating field seen by the spins and calculating the correlation functions using the diffusion-theory Green's function. The results of both calculations were shown to agreemore » for a special case. In the present work, we show that the eigenfunction expansion of the Torrey equation yields the expansion of the Green's function for the diffusion equation, thus showing the identity of this approach with that of the Redfield theory. The general solution can also be obtained directly from the Torrey equation for the density matrix. Thus, the physical content of the Redfield and Torrey approaches are identical. We then introduce a more general expression for the position autocorrelation function of particles moving in a closed cell, extending the range of applicability of the theory.« less

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.

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.

Quantum teleportation from a propagating photon to a solid-state spin qubit

NASA Astrophysics Data System (ADS)

Gao, W. B.; Fallahi, P.; Togan, E.; Delteil, A.; Chin, Y. S.; Miguel-Sanchez, J.; Imamoğlu, A.

2013-11-01

A quantum interface between a propagating photon used to transmit quantum information and a long-lived qubit used for storage is of central interest in quantum information science. A method for implementing such an interface between dissimilar qubits is quantum teleportation. Here we experimentally demonstrate transfer of quantum information carried by a photon to a semiconductor spin using quantum teleportation. In our experiment, a single photon in a superposition state is generated using resonant excitation of a neutral dot. To teleport this photonic qubit, we generate an entangled spin-photon state in a second dot located 5 m away and interfere the photons from the two dots in a Hong-Ou-Mandel set-up. Thanks to an unprecedented degree of photon-indistinguishability, a coincidence detection at the output of the interferometer heralds successful teleportation, which we verify by measuring the resulting spin state after prolonging its coherence time by optical spin-echo.

Quantum teleportation from a propagating photon to a solid-state spin qubit.

PubMed

Gao, W B; Fallahi, P; Togan, E; Delteil, A; Chin, Y S; Miguel-Sanchez, J; Imamoğlu, A

2013-01-01

A quantum interface between a propagating photon used to transmit quantum information and a long-lived qubit used for storage is of central interest in quantum information science. A method for implementing such an interface between dissimilar qubits is quantum teleportation. Here we experimentally demonstrate transfer of quantum information carried by a photon to a semiconductor spin using quantum teleportation. In our experiment, a single photon in a superposition state is generated using resonant excitation of a neutral dot. To teleport this photonic qubit, we generate an entangled spin-photon state in a second dot located 5 m away and interfere the photons from the two dots in a Hong-Ou-Mandel set-up. Thanks to an unprecedented degree of photon-indistinguishability, a coincidence detection at the output of the interferometer heralds successful teleportation, which we verify by measuring the resulting spin state after prolonging its coherence time by optical spin-echo.

Bifurcation analysis and phase diagram of a spin-string model with buckled states.

PubMed

Ruiz-Garcia, M; Bonilla, L L; Prados, A

2017-12-01

We analyze a one-dimensional spin-string model, in which string oscillators are linearly coupled to their two nearest neighbors and to Ising spins representing internal degrees of freedom. String-spin coupling induces a long-range ferromagnetic interaction among spins that competes with a spin-spin antiferromagnetic coupling. As a consequence, the complex phase diagram of the system exhibits different flat rippled and buckled states, with first or second order transition lines between states. This complexity translates to the two-dimensional version of the model, whose numerical solution has been recently used to explain qualitatively the rippled to buckled transition observed in scanning tunneling microscopy experiments with suspended graphene sheets. Here we describe in detail the phase diagram of the simpler one-dimensional model and phase stability using bifurcation theory. This gives additional insight into the physical mechanisms underlying the different phases and the behavior observed in experiments.

Bifurcation analysis and phase diagram of a spin-string model with buckled states

NASA Astrophysics Data System (ADS)

Ruiz-Garcia, M.; Bonilla, L. L.; Prados, A.

2017-12-01

We analyze a one-dimensional spin-string model, in which string oscillators are linearly coupled to their two nearest neighbors and to Ising spins representing internal degrees of freedom. String-spin coupling induces a long-range ferromagnetic interaction among spins that competes with a spin-spin antiferromagnetic coupling. As a consequence, the complex phase diagram of the system exhibits different flat rippled and buckled states, with first or second order transition lines between states. This complexity translates to the two-dimensional version of the model, whose numerical solution has been recently used to explain qualitatively the rippled to buckled transition observed in scanning tunneling microscopy experiments with suspended graphene sheets. Here we describe in detail the phase diagram of the simpler one-dimensional model and phase stability using bifurcation theory. This gives additional insight into the physical mechanisms underlying the different phases and the behavior observed in experiments.

Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond

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

Farfurnik, D.; Jarmola, A.; Pham, L. M.

2015-08-24

In this study, we demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T 1 effects and DD microwave pulses are used to increase the transverse coherence time T 2 from ~0.7ms up to ~30ms. Furthermore, we extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We also identify that themore » optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.« less

Unifying Exchange Sensitivity in Transition-Metal Spin-State Ordering and Catalysis through Bond Valence Metrics.

PubMed

Gani, Terry Z H; Kulik, Heather J

2017-11-14

Accurate predictions of spin-state ordering, reaction energetics, and barrier heights are critical for the computational discovery of open-shell transition-metal (TM) catalysts. Semilocal approximations in density functional theory, such as the generalized gradient approximation (GGA), suffer from delocalization error that causes them to overstabilize strongly bonded states. Descriptions of energetics and bonding are often improved by introducing a fraction of exact exchange (e.g., erroneous low-spin GGA ground states are instead correctly predicted as high-spin with a hybrid functional). The degree of spin-splitting sensitivity to exchange can be understood based on the chemical composition of the complex, but the effect of exchange on reaction energetics within a single spin state is less well-established. Across a number of model iron complexes, we observe strong exchange sensitivities of reaction barriers and energies that are of the same magnitude as those for spin splitting energies. We rationalize trends in both reaction and spin energetics by introducing a measure of delocalization, the bond valence of the metal-ligand bonds in each complex. The bond valence thus represents a simple-to-compute property that unifies understanding of exchange sensitivity for catalytic properties and spin-state ordering in TM complexes. Close agreement of the resulting per-metal-organic-bond sensitivity estimates, together with failure of alternative descriptors demonstrates the utility of the bond valence as a robust descriptor of how differences in metal-ligand delocalization produce differing relative energetics with exchange tuning. Our unified description explains the overall effect of exact exchange tuning on the paradigmatic two-state FeO + /CH 4 reaction that combines challenges of spin-state and reactivity predictions. This new descriptor-sensitivity relationship provides a path to quantifying how predictions in transition-metal complex screening are sensitive to the

NMR Spin-Lock Induced Crossing (SLIC) Dispersion and Long-Lived Spin States of Gaseous Propane at Low Magnetic Field (0.05 T)

PubMed Central

Barskiy, Danila A.; Salnikov, Oleg G.; Romanov, Alexey S.; Feldman, Matthew A.; Coffey, Aaron M.; Kovtunov, Kirill V.; Koptyug, Igor V.; Chekmenev, Eduard Y.

2017-01-01

When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05 T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the spin-lock induced crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect 1H NMR signal directly at 0.05 T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane. We also measured the exponential decay time constants (TLLSS or TS) of these pseudo-singlet long-lived spin states (LLSS) by varying the time between hyperpolarized propane production and SLIC detection. We have found that, on average, TS is approximately 3 times longer than the corresponding T1 value under the same conditions in the range of pressures studied (up to 7.6 atm). Moreover, TS may exceed 13 seconds at pressures above 7 atm in the gas phase. These results are in agreement with the previous reports, and they corroborate a great potential of long-lived hyperpolarized propane as an inhalable gaseous contrast agent for lung imaging and as a molecular tracer to study porous media using low-field NMR and MRI. PMID:28152435

NMR Spin-Lock Induced Crossing (SLIC) dispersion and long-lived spin states of gaseous propane at low magnetic field (0.05 T)

NASA Astrophysics Data System (ADS)

Barskiy, Danila A.; Salnikov, Oleg G.; Romanov, Alexey S.; Feldman, Matthew A.; Coffey, Aaron M.; Kovtunov, Kirill V.; Koptyug, Igor V.; Chekmenev, Eduard Y.

2017-03-01

When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05 T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the Spin-Lock Induced Crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect 1H NMR signal directly at 0.05 T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane. We also measured the exponential decay time constants (TLLSS or TS) of these pseudo-singlet long-lived spin states (LLSS) by varying the time between hyperpolarized propane production and SLIC detection. We have found that, on average, TS is approximately 3 times longer than the corresponding T1 value under the same conditions in the range of pressures studied (up to 7.6 atm). Moreover, TS may exceed 13 s at pressures above 7 atm in the gas phase. These results are in agreement with the previous reports, and they corroborate a great potential of long-lived hyperpolarized propane as an inhalable gaseous contrast agent for lung imaging and as a molecular tracer to study porous media using low-field NMR and MRI.

Quantum entanglement between an optical photon and a solid-state spin qubit.

PubMed

Togan, E; Chu, Y; Trifonov, A S; Jiang, L; Maze, J; Childress, L; Dutt, M V G; Sørensen, A S; Hemmer, P R; Zibrov, A S; Lukin, M D

2010-08-05

Quantum entanglement is among the most fascinating aspects of quantum theory. Entangled optical photons are now widely used for fundamental tests of quantum mechanics and applications such as quantum cryptography. Several recent experiments demonstrated entanglement of optical photons with trapped ions, atoms and atomic ensembles, which are then used to connect remote long-term memory nodes in distributed quantum networks. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks.

Spin-Orbit Coupling Controlled J = 3 / 2 Electronic Ground State in 5 d 3 Oxides

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

Taylor, A. E.; Calder, S.; Morrow, R.

Entanglement of spin and orbital degrees of freedom drives the formation of novel quantum and topological physical states. Here we report resonant inelastic x-ray scattering measurements of the transition metal oxides Ca3LiOsO6 and Ba2YOsO6, which reveals a dramatic spitting of the t2g manifold. We invoke an intermediate coupling approach that incorporates both spin-orbit coupling and electron-electron interactions on an even footing and reveal that the ground state of 5d3-based compounds, which has remained elusive in previously applied models, is a novel spin-orbit entangled J=3/2 electronic ground state. This work reveals the hidden diversity of spin-orbit controlled ground states in 5dmore » systems and introduces a new arena in the search for spin-orbit controlled phases of matter.« less

Direct Measurement of the Flip-Flop Rate of Electron Spins in the Solid State

NASA Astrophysics Data System (ADS)

Dikarov, Ekaterina; Zgadzai, Oleg; Artzi, Yaron; Blank, Aharon

2016-10-01

Electron spins in solids have a central role in many current and future spin-based devices, ranging from sensitive sensors to quantum computers. Many of these apparatuses rely on the formation of well-defined spin structures (e.g., a 2D array) with controlled and well-characterized spin-spin interactions. While being essential for device operation, these interactions can also result in undesirable effects, such as decoherence. Arguably, the most important pure quantum interaction that causes decoherence is known as the "flip-flop" process, where two interacting spins interchange their quantum state. Currently, for electron spins, the rate of this process can only be estimated theoretically, or measured indirectly, under limiting assumptions and approximations, via spin-relaxation data. This work experimentally demonstrates how the flip-flop rate can be directly and accurately measured by examining spin-diffusion processes in the solid state for physically fixed spins. Under such terms, diffusion can occur only through this flip-flop-mediated quantum-state exchange and not via actual spatial motion. Our approach is implemented on two types of samples, phosphorus-doped 28Si and nitrogen vacancies in diamond, both of which are significantly relevant to quantum sensors and information processing. However, while the results for the former sample are conclusive and reveal a flip-flop rate of approximately 12.3 Hz, for the latter sample only an upper limit of approximately 0.2 Hz for this rate can be estimated.

Graph state generation with noisy mirror-inverting spin chains

NASA Astrophysics Data System (ADS)

Clark, Stephen R.; Klein, Alexander; Bruderer, Martin; Jaksch, Dieter

2007-06-01

We investigate the influence of noise on a graph state generation scheme which exploits a mirror inverting spin chain. Within this scheme the spin chain is used repeatedly as an entanglement bus (EB) to create multi-partite entanglement. The noise model we consider comprises of each spin of this EB being exposed to independent local noise which degrades the capabilities of the EB. Here we concentrate on quantifying its performance as a single-qubit channel and as a mediator of a two-qubit entangling gate, since these are basic operations necessary for graph state generation using the EB. In particular, for the single-qubit case we numerically calculate the average channel fidelity and whether the channel becomes entanglement breaking, i.e. expunges any entanglement the transferred qubit may have with other external qubits. We find that neither local decay nor dephasing noise cause entanglement breaking. This is in contrast to local thermal and depolarizing noise where we determine a critical length and critical noise coupling, respectively, at which entanglement breaking occurs. The critical noise coupling for local depolarizing noise is found to exhibit a power-law dependence on the chain length. For two-qubits we similarly compute the average gate fidelity and whether the ability for this gate to create entanglement is maintained. The concatenation of these noisy gates for the construction of a five-qubit linear cluster state and a Greenberger Horne Zeilinger state indicates that the level of noise that can be tolerated for graph state generation is tightly constrained.

Ground-state information geometry and quantum criticality in an inhomogeneous spin model

NASA Astrophysics Data System (ADS)

Ma, Yu-Quan

2015-09-01

We investigate the ground-state Riemannian metric and the cyclic quantum distance of an inhomogeneous quantum spin-1/2 chain in a transverse field. This model can be diagonalized by using a general canonical transformation to the fermionic Hamiltonian mapped from the spin system. The ground-state Riemannian metric is derived exactly on a parameter manifold ring S1, which is introduced by performing a gauge transformation to the spin Hamiltonian through a twist operator. The cyclic ground-state quantum distance and the second derivative of the ground-state energy are studied in different exchange coupling parameter regions. Particularly, we show that, in the case of exchange coupling parameter Ja = Jb, the quantum ferromagnetic phase can be characterized by an invariant quantum distance and this distance will decay to zero rapidly in the paramagnetic phase. Project supported by the National Natural Science Foundation of China (Grant Nos. 11404023 and 11347131).

Spin injection and inverse Edelstein effect in the surface states of topological Kondo insulator SmB6

PubMed Central

Song, Qi; Mi, Jian; Zhao, Dan; Su, Tang; Yuan, Wei; Xing, Wenyu; Chen, Yangyang; Wang, Tianyu; Wu, Tao; Chen, Xian Hui; Xie, X. C.; Zhang, Chi; Shi, Jing; Han, Wei

2016-01-01

There has been considerable interest in exploiting the spin degrees of freedom of electrons for potential information storage and computing technologies. Topological insulators (TIs), a class of quantum materials, have special gapless edge/surface states, where the spin polarization of the Dirac fermions is locked to the momentum direction. This spin–momentum locking property gives rise to very interesting spin-dependent physical phenomena such as the Edelstein and inverse Edelstein effects. However, the spin injection in pure surface states of TI is very challenging because of the coexistence of the highly conducting bulk states. Here, we experimentally demonstrate the spin injection and observe the inverse Edelstein effect in the surface states of a topological Kondo insulator, SmB6. At low temperatures when only surface carriers are present, a clear spin signal is observed. Furthermore, the magnetic field angle dependence of the spin signal is consistent with spin–momentum locking property of surface states of SmB6. PMID:27834378

Spin injection and inverse Edelstein effect in the surface states of topological Kondo insulator SmB 6

DOE PAGES

Song, Qi; Mi, Jian; Zhao, Dan; ...

2016-11-11

There has been considerable interest in exploiting the spin degrees of freedom of electrons for potential information storage and computing technologies. Topological insulators (TIs), a class of quantum materials, have special gapless edge/surface states, where the spin polarization of the Dirac fermions is locked to the momentum direction. This spin–momentum locking property gives rise to very interesting spin-dependent physical phenomena such as the Edelstein and inverse Edelstein effects. However, the spin injection in pure surface states of TI is very challenging because of the coexistence of the highly conducting bulk states. Here, we experimentally demonstrate the spin injection and observemore » the inverse Edelstein effect in the surface states of a topological Kondo insulator, SmB 6. At low temperatures when only surface carriers are present, a clear spin signal is observed. Moreover, the magnetic field angle dependence of the spin signal is consistent with spin–momentum locking property of surface states of SmB6.« less

Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

NASA Astrophysics Data System (ADS)

He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

2017-08-01

Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

Suppression of spin-state transition in epitaxially strained LaCoO3

NASA Astrophysics Data System (ADS)

Pinta, C.; Fuchs, D.; Merz, M.; Wissinger, M.; Arac, E.; v. Löhneysen, H.; Samartsev, A.; Nagel, P.; Schuppler, S.

2008-11-01

Epitaxial thin films of LaCoO3 (e-LCO) exhibit ferromagnetic order with a transition temperature TC=85K while polycrystalline thin LaCoO3 films (p-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both e-LCO and p-LCO was studied by x-ray absorption spectroscopy at the CoL2,3 and OK edges. Considerable spectral redistributions over temperature are observed for p-LCO . The spectra for e-LCO , on the other hand, do not show any significant changes for temperatures between 30 and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S=0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in e-LCO thin films.

Analytical approaches to the determination of spin-dependent parton distribution functions at NNLO approximation

NASA Astrophysics Data System (ADS)

Salajegheh, Maral; Nejad, S. Mohammad Moosavi; Khanpour, Hamzeh; Tehrani, S. Atashbar

2018-05-01

In this paper, we present SMKA18 analysis, which is a first attempt to extract the set of next-to-next-leading-order (NNLO) spin-dependent parton distribution functions (spin-dependent PDFs) and their uncertainties determined through the Laplace transform technique and Jacobi polynomial approach. Using the Laplace transformations, we present an analytical solution for the spin-dependent Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations at NNLO approximation. The results are extracted using a wide range of proton g1p(x ,Q2) , neutron g1n(x ,Q2) , and deuteron g1d(x ,Q2) spin-dependent structure functions data set including the most recent high-precision measurements from COMPASS16 experiments at CERN, which are playing an increasingly important role in global spin-dependent fits. The careful estimations of uncertainties have been done using the standard Hessian error propagation. We will compare our results with the available spin-dependent inclusive deep inelastic scattering data set and other results for the spin-dependent PDFs in literature. The results obtained for the spin-dependent PDFs as well as spin-dependent structure functions are clearly explained both in the small and large values of x .

Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR line shape

NASA Astrophysics Data System (ADS)

Zschocke, Fabian; Vojta, Matthias

2015-07-01

Kitaev's compass model on the honeycomb lattice realizes a spin liquid whose emergent excitations are dispersive Majorana fermions and static Z2 gauge fluxes. We discuss the proper selection of physical states for finite-size simulations in the Majorana representation, based on a recent paper by F. L. Pedrocchi, S. Chesi, and D. Loss [Phys. Rev. B 84, 165414 (2011), 10.1103/PhysRevB.84.165414]. Certain physical observables acquire large finite-size effects, in particular if the ground state is not fermion-free, which we prove to generally apply to the system in the gapless phase and with periodic boundary conditions. To illustrate our findings, we compute the static and dynamic spin susceptibilities for finite-size systems. Specifically, we consider random-bond disorder (which preserves the solubility of the model), calculate the distribution of local flux gaps, and extract the NMR line shape. We also predict a transition to a random-flux state with increasing disorder.

In-beam spectroscopy of medium- and high-spin states in Ce 133

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

Ayangeakaa, A. D.; Garg, U.; Petrache, C. M.

2016-05-01

Medium and high-spin states in Ce-133 were investigated using the Cd-116(Ne-22, 5n) reaction and the Gammasphere array. The level scheme was extended up to an excitation energy of similar to 22.8 MeV and spin 93/2 (h) over bar. Eleven bands of quadrupole transitions and two new dipole bands are identified. The connections to low-lying states of the previously known, high-spin triaxial bands were firmly established, thus fixing the excitation energy and, in many cases, the spin parity of the levels. Based on comparisons with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant density functional theory, it is shown that allmore » observed bands are characterized by pronounced triaxiality. Competing multiquasiparticle configurations are found to contribute to a rich variety of collective phenomena in this nucleus.« less

29 CFR 779.251 - Goods that have lost their out-of-State identity.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 3 2010-07-01 2010-07-01 false Goods that have lost their out-of-State identity. 779.251... Coverage Interstate Inflow Test Under Prior Act § 779.251 Goods that have lost their out-of-State identity... been processed or manufactured so as to have lost their identity as out-of-State goods before they are...

29 CFR 779.251 - Goods that have lost their out-of-State identity.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 3 2012-07-01 2012-07-01 false Goods that have lost their out-of-State identity. 779.251... Coverage Interstate Inflow Test Under Prior Act § 779.251 Goods that have lost their out-of-State identity... been processed or manufactured so as to have lost their identity as out-of-State goods before they are...

29 CFR 779.251 - Goods that have lost their out-of-State identity.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 3 2014-07-01 2014-07-01 false Goods that have lost their out-of-State identity. 779.251... Coverage Interstate Inflow Test Under Prior Act § 779.251 Goods that have lost their out-of-State identity... been processed or manufactured so as to have lost their identity as out-of-State goods before they are...

29 CFR 779.251 - Goods that have lost their out-of-State identity.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 3 2011-07-01 2011-07-01 false Goods that have lost their out-of-State identity. 779.251... Coverage Interstate Inflow Test Under Prior Act § 779.251 Goods that have lost their out-of-State identity... been processed or manufactured so as to have lost their identity as out-of-State goods before they are...

29 CFR 779.251 - Goods that have lost their out-of-State identity.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 3 2013-07-01 2013-07-01 false Goods that have lost their out-of-State identity. 779.251... Coverage Interstate Inflow Test Under Prior Act § 779.251 Goods that have lost their out-of-State identity... been processed or manufactured so as to have lost their identity as out-of-State goods before they are...

Flight Guidance System Validation Using SPIN

NASA Technical Reports Server (NTRS)

Naydich, Dimitri; Nowakowski, John

1998-01-01

To verify the requirements for the mode control logic of a Flight Guidance System (FGS) we applied SPIN, a widely used software package that supports the formal verification of distributed systems. These requirements, collectively called the FGS specification, were developed at Rockwell Avionics & Communications and expressed in terms of the Consortium Requirements Engineering (CoRE) method. The properties to be verified are the invariants formulated in the FGS specification, along with the standard properties of consistency and completeness. The project had two stages. First, the FGS specification and the properties to be verified were reformulated in PROMELA, the input language of SPIN. This involved a semantics issue, as some constructs of the FGS specification do not have well-defined semantics in CoRE. Then we attempted to verify the requirements' properties using the automatic model checking facilities of SPIN. Due to the large size of the state space of the FGS specification an exhaustive state space analysis with SPIN turned out to be impossible. So we used the supertrace model checking procedure of SPIN that provides for a partial analysis of the state space. During this process, we found some subtle errors in the FGS specification.

Entanglement and quantum state geometry of a spin system with all-range Ising-type interaction

NASA Astrophysics Data System (ADS)

Kuzmak, A. R.

2018-04-01

The evolution of an N spin-1/2 system with all-range Ising-type interaction is considered. For this system we study the entanglement of one spin with the rest spins. It is shown that the entanglement depends on the number of spins and the initial state. Also, the geometry of the manifold, which contains entangled states, is obtained. For this case we find the dependence of entanglement on the scalar curvature of the manifold and examine it for different numbers of spins in the system. Finally we show that the transverse magnetic field leads to a change in the manifold topology.

Room-temperature storage of quantum entanglement using decoherence-free subspace in a solid-state spin system

NASA Astrophysics Data System (ADS)

Wang, F.; Huang, Y.-Y.; Zhang, Z.-Y.; Zu, C.; Hou, P.-Y.; Yuan, X.-X.; Wang, W.-B.; Zhang, W.-G.; He, L.; Chang, X.-Y.; Duan, L.-M.

2017-10-01

We experimentally demonstrate room-temperature storage of quantum entanglement using two nuclear spins weakly coupled to the electronic spin carried by a single nitrogen-vacancy center in diamond. We realize universal quantum gate control over the three-qubit spin system and produce entangled states in the decoherence-free subspace of the two nuclear spins. By injecting arbitrary collective noise, we demonstrate that the decoherence-free entangled state has coherence time longer than that of other entangled states by an order of magnitude in our experiment.

Laser photoelectron spectroscopy of MnH - and FeH - : Electronic structures of the metal hydrides, identification of a low-spin excited state of MnH, and evidence for a low-spin ground state of FeH

NASA Astrophysics Data System (ADS)

Stevens, Amy E.; Feigerle, C. S.; Lineberger, W. C.

1983-05-01

The laser photoelectron spectra of MnH- and MnD-, and FeH- and FeD- are reported. A qualitative description of the electronic structure of the low-spin and high-spin states of the metal hydrides is developed, and used to interpret the spectra. A diagonal transition in the photodetachment to the known high-spin, 7Σ+, ground state of MnH is observed. An intense off-diagonal transition to a state of MnH, at 1725±50 cm-1 excitation energy, is attributed to loss of an antibonding electron from MnH-, to yield a low-spin quintet state of MnH. For FeH- the photodetachment to the ground state is an off-diagonal transition, attributed to loss of the antibonding electron from FeH-, to yield a low-spin quartet ground state of FeH. A diagonal transition results in an FeH state at 1945±55 cm-1; this state of FeH is assigned as the lowest-lying high-spin sextet state of FeH. An additional excited state of MnH and two other excited states of FeH are observed. Excitation energies for all the states are reported; vibrational frequencies and bond lengths for the ions and several states of the neutrals are also determined from the spectra. The electron affinity of MnH is found to be 0.869±0.010 eV; and the electron affinity of FeH is determined to be 0.934±0.011 eV. Spectroscopic constants for the various deuterides are also reported.

Bilinear magnetoelectric resistance as a probe of three-dimensional spin texture in topological surface states

DOE PAGES

He, Pan; Zhang, Steven S. -L.; Zhu, Dapeng; ...

2018-02-05

Surface states of three-dimensional topological insulators exhibit the phenomenon of spin-momentum locking, whereby the orientation of an electron spin is determined by its momentum. Probing the spin texture of these states is of critical importance for the realization of topological insulator devices, but the main technique currently available is spin-and angle-resolved photoemission spectroscopy. Here in this paper we reveal a close link between the spin texture and a new kind of magnetoresistance, which depends on the relative orientation of the current with respect to the magnetic field as well as the crystallographic axes, and scales linearly with both the appliedmore » electric and magnetic fields. This bilinear magnetoelectric resistance can be used to map the spin texture of topological surface states by simple transport measurements. For a prototypical Bi 2Se 3 single layer, we can map both the in-plane and out-of-plane components of the spin texture (the latter arising from hexagonal warping). Theoretical calculations suggest that the bilinear magnetoelectric resistance originates from conversion of a non-equilibrium spin current into a charge current under application of the external magnetic field.« less

Bilinear magnetoelectric resistance as a probe of three-dimensional spin texture in topological surface states

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

He, Pan; Zhang, Steven S. -L.; Zhu, Dapeng

Surface states of three-dimensional topological insulators exhibit the phenomenon of spin-momentum locking, whereby the orientation of an electron spin is determined by its momentum. Probing the spin texture of these states is of critical importance for the realization of topological insulator devices, but the main technique currently available is spin-and angle-resolved photoemission spectroscopy. Here in this paper we reveal a close link between the spin texture and a new kind of magnetoresistance, which depends on the relative orientation of the current with respect to the magnetic field as well as the crystallographic axes, and scales linearly with both the appliedmore » electric and magnetic fields. This bilinear magnetoelectric resistance can be used to map the spin texture of topological surface states by simple transport measurements. For a prototypical Bi 2Se 3 single layer, we can map both the in-plane and out-of-plane components of the spin texture (the latter arising from hexagonal warping). Theoretical calculations suggest that the bilinear magnetoelectric resistance originates from conversion of a non-equilibrium spin current into a charge current under application of the external magnetic field.« less

Bilinear magnetoelectric resistance as a probe of three-dimensional spin texture in topological surface states

NASA Astrophysics Data System (ADS)

He, Pan; Zhang, Steven S.-L.; Zhu, Dapeng; Liu, Yang; Wang, Yi; Yu, Jiawei; Vignale, Giovanni; Yang, Hyunsoo

2018-05-01

Surface states of three-dimensional topological insulators exhibit the phenomenon of spin-momentum locking, whereby the orientation of an electron spin is determined by its momentum. Probing the spin texture of these states is of critical importance for the realization of topological insulator devices, but the main technique currently available is spin- and angle-resolved photoemission spectroscopy. Here we reveal a close link between the spin texture and a new kind of magnetoresistance, which depends on the relative orientation of the current with respect to the magnetic field as well as the crystallographic axes, and scales linearly with both the applied electric and magnetic fields. This bilinear magnetoelectric resistance can be used to map the spin texture of topological surface states by simple transport measurements. For a prototypical Bi2Se3 single layer, we can map both the in-plane and out-of-plane components of the spin texture (the latter arising from hexagonal warping). Theoretical calculations suggest that the bilinear magnetoelectric resistance originates from conversion of a non-equilibrium spin current into a charge current under application of the external magnetic field.

Spin-dependent Electron Correlations of a System with Broken Spin Symmetry

NASA Astrophysics Data System (ADS)

Yi, K. S.; Kim, J. I.; Kim, J. S.

2001-04-01

The spin-dependent local field corrections Gσ, σ'/ (q, ω) of a spin-polarized electron gas(SPEG) are examined within a genralized RPA. Numerical results of Gσ, σ/ (q, 0) for both the majority and minority spin electrons of SPEG show a complicated but interesting behavior as one varies the spin polarization ζ of the SPEG. A pronounced maximum in Gσ, σ/ (q, 0) is observed and the location of the peaks are found to depend strongly on the values of ζ. We also show some numerical results of the mixed susceptibilities χem and χme, which are finite and not identical in SPEG.

Spin liquid state in the 3D frustrated antiferromagnet PbCuTe 2 O 6 : NMR and muon spin relaxation studies

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

Khuntia, P.; Bert, F.; Mendels, P.

In this study, PbCuTe 2O 6 is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu 2+ ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointingmore » to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T 1 NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.« less

Spin liquid state in the 3D frustrated antiferromagnet PbCuTe 2 O 6 : NMR and muon spin relaxation studies

DOE PAGES

Khuntia, P.; Bert, F.; Mendels, P.; ...

2016-03-11

In this study, PbCuTe 2O 6 is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu 2+ ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointingmore » to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T 1 NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.« less

Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases.

PubMed

Zhou, Tao; Gao, Yi; Wang, Z D

2014-06-11

We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.

Resolution of the EPR Paradox for Fermion Spin Correlations

NASA Astrophysics Data System (ADS)

Close, Robert

2011-10-01

The EPR paradox addresses the question of whether a physical system can have a definite state independent of its measurement. Bell's Theorem places limits on correlations between local measurements of particles whose properties are established prior to measurement. Experimental violation of Bell's theorem has been regarded as evidence against the existence of a definite state prior to measurement. We model fermions as having a spatial distribution of spin values, so that a Stern-Gerlach device samples the spin distribution differently at different orientations. The computed correlations agree with quantum mechanical predictions and experimental observations. Bell's Theorem is not applicable because for any sampling of angles, different points on the sphere have different density of states.

Collins-Soper equation for the energy evolution of transverse-momentum and spin dependent parton distributions

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

Idilbi, Ahmad; Ji Xiangdong; Yuan Feng

The hadron-energy evolution (Collins and Soper) equation for all the leading-twist transverse-momentum and spin dependent parton distributions is derived in the impact parameter space. Based on this equation, we present a resummation formulas for the spin dependent structure functions of the semi-inclusive deep-inelastic scattering.

Dynamics of interacting fermions under spin-orbit coupling in an optical lattice clock

NASA Astrophysics Data System (ADS)

Bromley, S. L.; Kolkowitz, S.; Bothwell, T.; Kedar, D.; Safavi-Naini, A.; Wall, M. L.; Salomon, C.; Rey, A. M.; Ye, J.

2018-04-01

Quantum statistics and symmetrization dictate that identical fermions do not interact via s-wave collisions. However, in the presence of spin-orbit coupling (SOC), fermions prepared in identical internal states with distinct momenta become distinguishable. The resulting strongly interacting system can exhibit exotic topological and pairing behaviours, many of which are yet to be observed in condensed matter systems. Ultracold atomic gases offer a promising pathway for simulating these rich phenomena, but until recently have been hindered by heating and losses. Here we enter a new regime of many-body interacting SOC in a fermionic optical lattice clock (OLC), where the long-lived electronic clock states mitigate unwanted dissipation. Using clock spectroscopy, we observe the precession of the collective magnetization and the emergence of spin-locking effects arising from an interplay between p-wave and SOC-induced exchange interactions. The many-body dynamics are well captured by a collective XXZ spin model, which describes a broad class of condensed matter systems ranging from superconductors to quantum magnets. Furthermore, our work will aid in the design of next-generation OLCs by offering a route for avoiding the observed large density shifts caused by SOC-induced exchange interactions.

Disorder and Quantum Spin Ice

NASA Astrophysics Data System (ADS)

Martin, N.; Bonville, P.; Lhotel, E.; Guitteny, S.; Wildes, A.; Decorse, C.; Ciomaga Hatnean, M.; Balakrishnan, G.; Mirebeau, I.; Petit, S.

2017-10-01

We report on diffuse neutron scattering experiments providing evidence for the presence of random strains in the quantum spin-ice candidate Pr2Zr2O7 . Since Pr3 + is a non-Kramers ion, the strain deeply modifies the picture of Ising magnetic moments governing the low-temperature properties of this material. It is shown that the derived strain distribution accounts for the temperature dependence of the specific heat and of the spin-excitation spectra. Taking advantage of mean-field and spin-dynamics simulations, we argue that the randomness in Pr2Zr2O7 promotes a new state of matter, which is disordered yet characterized by short-range antiferroquadrupolar correlations, and from which emerge spin-ice-like excitations. Thus, this study gives an original research route in the field of quantum spin ice.

Fast generation of spin-squeezed states in bosonic Josephson junctions

NASA Astrophysics Data System (ADS)

Juliá-Díaz, B.; Torrontegui, E.; Martorell, J.; Muga, J. G.; Polls, A.

2012-12-01

We describe methods for the fast production of highly coherent-spin-squeezed many-body states in bosonic Josephson junctions. We start from the known mapping of the two-site Bose-Hubbard (BH) Hamiltonian to that of a single effective particle evolving according to a Schrödinger-like equation in Fock space. Since, for repulsive interactions, the effective potential in Fock space is nearly parabolic, we extend recently derived protocols for shortcuts to adiabatic evolution in harmonic potentials to the many-body BH Hamiltonian. A comparison with current experiments shows that our methods allow for an important reduction in the preparation times of highly squeezed spin states.

Laser-induced polarization of a quantum spin system in the steady-state regime

NASA Astrophysics Data System (ADS)

Zvyagin, A. A.

2016-05-01

The effect of the circularly polarized laser field on quantum spin systems in the steady-state regime, in which relaxation plays the central role, has been studied. The dynamical mean-field-like theory predicts several general results for the behavior of the time-average magnetization caused by the laser field. The induced magnetization oscillates with the frequency of the laser field (while Rabi-like oscillations, which modulate the latter in the dynamical regime, are damped by the relaxation in the steady-state regime). At high frequencies, that magnetization is determined by the value to which the relaxation process is directed. At low frequencies the slope of that magnetization as a function of the frequency is determined by the strength of the laser field. The anisotropy determines the resonance behavior of the time-averaged magnetization in both the ferromagnetic and antiferromagnetic cases with nonzero magnetic anisotropy. Nonlinear effects (in the magnitude of the laser field) have been considered. The effect of the laser field on quantum spin systems is maximal in resonance, where the time-averaged magnetization, caused by the laser field, is changed essentially. Out of resonance the changes in the magnetization are relatively small. The resonance effect is caused by the nonzero magnetic anisotropy. The resonance frequency is small (proportional to the anisotropy value) for spin systems with ferromagnetic interactions and enhanced by exchange interactions in the spin systems with antiferromagnetic couplings. We show that it is worthwhile to study the laser-field-induced magnetization of quantum spin systems caused by the high-frequency laser field in the steady-state regime in "easy-axis" antiferromagnetic spin systems (e.g., in Ising-like antiferromagnetic spin-chain materials). The effects of the Dzyaloshinskii-Moriya interaction and the spin-frustration couplings (in the case of the zigzag spin chain) have been analyzed.

Spatial separation and entanglement of identical particles

NASA Astrophysics Data System (ADS)

Cunden, Fabio Deelan; di Martino, Sara; Facchi, Paolo; Florio, Giuseppe

2014-04-01

We reconsider the effect of indistinguishability on the reduced density operator of the internal degrees of freedom (tracing out the spatial degrees of freedom) for a quantum system composed of identical particles located in different spatial regions. We explicitly show that if the spin measurements are performed in disjoint spatial regions then there are no constraints on the structure of the reduced state of the system. This implies that the statistics of identical particles has no role from the point of view of separability and entanglement when the measurements are spatially separated. We extend the treatment to the case of n particles and show the connection with some recent criteria for separability based on subalgebras of observables.

Distinguishing Identical Particles and the Correct Counting of States

ERIC Educational Resources Information Center

de la Torre, A. C.; Martin, H. O.

2009-01-01

It is shown that quantum systems of identical particles can be treated as different when they are in well-differentiated states. This simplifying assumption allows for the consideration of quantum systems isolated from the rest of the universe and justifies many intuitive statements about identical systems. However, it is shown that this…

29 CFR 779.250 - Goods that have not lost their out-of-State identity.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 3 2010-07-01 2010-07-01 false Goods that have not lost their out-of-State identity. 779...-State identity. Goods which are purchased or received by the enterprise from within the State will be... and have not lost their identity as out-of-State goods before they are purchased or received by the...

29 CFR 779.250 - Goods that have not lost their out-of-State identity.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 3 2011-07-01 2011-07-01 false Goods that have not lost their out-of-State identity. 779...-State identity. Goods which are purchased or received by the enterprise from within the State will be... and have not lost their identity as out-of-State goods before they are purchased or received by the...

29 CFR 779.250 - Goods that have not lost their out-of-State identity.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 3 2014-07-01 2014-07-01 false Goods that have not lost their out-of-State identity. 779...-State identity. Goods which are purchased or received by the enterprise from within the State will be... and have not lost their identity as out-of-State goods before they are purchased or received by the...

29 CFR 779.250 - Goods that have not lost their out-of-State identity.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 3 2013-07-01 2013-07-01 false Goods that have not lost their out-of-State identity. 779...-State identity. Goods which are purchased or received by the enterprise from within the State will be... and have not lost their identity as out-of-State goods before they are purchased or received by the...

29 CFR 779.250 - Goods that have not lost their out-of-State identity.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 3 2012-07-01 2012-07-01 false Goods that have not lost their out-of-State identity. 779...-State identity. Goods which are purchased or received by the enterprise from within the State will be... and have not lost their identity as out-of-State goods before they are purchased or received by the...

Polar-core spin vortex of quasi-2D ferromagnetic spin-1 condensate in a flat-bottomed optical trap with a weak magnetic field

NASA Astrophysics Data System (ADS)

Zheng, Gong-Ping; Li, Pin; Li, Ting; Xue, Ya-Jie

2018-02-01

Motivated by the recent experiments realized in a flat-bottomed optical trap (Navon et al., 2015; Chomaz et al., 2015), we study the ground state of polar-core spin vortex of quasi-2D ferromagnetic spin-1 condensate in a finite-size homogeneous trap with a weak magnetic field. The exact spatial distribution of local spin is obtained with a variational method. Unlike the fully-magnetized planar spin texture with a zero-spin core, which was schematically demonstrated in previous studies for the ideal polar-core spin vortex in a homogeneous trap with infinitely large boundary, some plateaus and two-cores structure emerge in the distribution curves of spin magnitude in the polar-core spin vortex we obtained for the larger effective spin-dependent interaction. More importantly, the spin values of the plateaus are not 1 as expected in the fully-magnetized spin texture, except for the sufficiently large spin-dependent interaction and the weak-magnetic-field limit. We attribute the decrease of spin value to the effect of finite size of the system. The spin values of the plateaus can be controlled by the quadratic Zeeman energy q of the weak magnetic field, which decreases with the increase of q.

On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

NASA Astrophysics Data System (ADS)

Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.

2015-12-01

It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

Strain-sensitive spin-state ordering in thin films of perovskite LaCoO3

NASA Astrophysics Data System (ADS)

Fujioka, J.; Yamasaki, Y.; Doi, A.; Nakao, H.; Kumai, R.; Murakami, Y.; Nakamura, M.; Kawasaki, M.; Arima, T.; Tokura, Y.

2015-11-01

We have investigated the lattice distortion coupled to the Co 3 d -spin-state ordering in thin films of perovskite LaCoO3 with various epitaxial strains by measurements of the magnetization, x-ray diffraction, and optical spectra. In the system with tensile strain about 0.5%, a lattice distortion characterized by the modulation vector q =(1 /6 ,1 /6 ,1 /6 ) emerges at 40 K, followed by a ferromagnetic ordering at 24 K. Alternatively, in systems with tensile strain exceeding 1%, the lattice distortion characterized by q =(1 /4 ,1 /4 ,1 /4 ) emerges at 120 K or higher, and subsequently the ferromagnetic or ferrimagnetic ordering occurs around 90 K. The evolution of infrared phonon spectra and resonant x-ray scattering at the Co K edge suggests that the population change in the Co 3 d spin state causes the strain-induced switching of spin-state ordering as well as of magnetic ordering in this canonical spin-state crossover system.

Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

DOE PAGES

Seo, Hosung; Govoni, Marco; Galli, Giulia

2016-02-15

Spin defects in wide-band gap semiconductors are promising systems for the realization of quantum bits, or qubits, in solid-state environments. To date, defect qubits have only been realized in materials with strong covalent bonds. Here, we introduce a strain-driven scheme to rationally design defect spins in functional ionic crystals, which may operate as potential qubits. In particular, using a combination of state-of-the-art ab-initio calculations based on hybrid density functional and many-body perturbation theory, we predicted that the negatively charged nitrogen vacancy center in piezoelectric aluminum nitride exhibits spin-triplet ground states under realistic uni- and bi-axial strain conditions; such states maymore » be harnessed for the realization of qubits. As a result, the strain-driven strategy adopted here can be readily extended to a wide range of point defects in other wide-band gap semiconductors, paving the way to controlling the spin properties of defects in ionic systems for potential spintronic technologies.« less

Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO4

NASA Astrophysics Data System (ADS)

Ma, Zhen; Wang, Jinghui; Dong, Zhao-Yang; Zhang, Jun; Li, Shichao; Zheng, Shu-Han; Yu, Yunjie; Wang, Wei; Che, Liqiang; Ran, Kejing; Bao, Song; Cai, Zhengwei; Čermák, P.; Schneidewind, A.; Yano, S.; Gardner, J. S.; Lu, Xin; Yu, Shun-Li; Liu, Jun-Ming; Li, Shiyan; Li, Jian-Xin; Wen, Jinsheng

2018-02-01

We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO4 as a spin glass, including no long-range magnetic order, prominent broad excitation continua, and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature ac susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compound YbMgGaO4 , which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase.

A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates

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

Wang, Hanquan, E-mail: hanquan.wang@gmail.com; Yunnan Tongchang Scientific Computing and Data Mining Research Center, Kunming, Yunnan Province, 650221

In this paper, a projection gradient method is presented for computing ground state of spin-2 Bose–Einstein condensates (BEC). We first propose the general projection gradient method for solving energy functional minimization problem under multiple constraints, in which the energy functional takes real functions as independent variables. We next extend the method to solve a similar problem, where the energy functional now takes complex functions as independent variables. We finally employ the method into finding the ground state of spin-2 BEC. The key of our method is: by constructing continuous gradient flows (CGFs), the ground state of spin-2 BEC can bemore » computed as the steady state solution of such CGFs. We discretized the CGFs by a conservative finite difference method along with a proper way to deal with the nonlinear terms. We show that the numerical discretization is normalization and magnetization conservative and energy diminishing. Numerical results of the ground state and their energy of spin-2 BEC are reported to demonstrate the effectiveness of the numerical method.« less

Revisiting spin-lattice relaxation time measurements for dilute spins in high-resolution solid-state NMR spectroscopy

NASA Astrophysics Data System (ADS)

Fu, Riqiang; Li, Jun; Cui, Jingyu; Peng, Xinhua

2016-07-01

Numerous nuclear magnetic resonance (NMR) measurements of spin-lattice relaxation times (T1S) for dilute spins such as 13C have led to investigations of the motional dynamics of individual functional groups in solid materials. In this work, we revisit the Solomon equations and analyze how the heteronuclear cross relaxation between the dilute S (e.g. 13C) and abundant I (e.g. 1H) spins affects the measured T1S values in solid-state NMR in the absence of 1H saturation during the recovery time. It is found theoretically that at the beginning of the S spin magnetization recovery, the existence of non-equilibrium I magnetization introduces the heteronuclear cross relaxation effect onto the recovery of the S spin magnetization and confirmed experimentally that such a heteronuclear cross relaxation effect results in the recovery overshoot phenomena for the dilute spins when T1S is on the same order of T1H, leading to inaccurate measurements of the T1S values. Even when T1S is ten times larger than T1H, the heteronuclear cross relaxation effect on the measured T1S values is still noticeable. Furthermore, this cross relaxation effect on recovery trajectory of the S spins can be manipulated and even suppressed by preparing the initial I and S magnetization, so as to obtain the accurate T1S values. A sample of natural abundance L-isoleucine powder has been used to demonstrate the T1S measurements and their corresponding measured T1C values under various experimental conditions.

Spin polarization properties of benzene/graphene with transition metals as dopants: First principles calculations

NASA Astrophysics Data System (ADS)

Yuan, X. B.; Tian, Y. L.; Zhao, X. W.; Yue, W. W.; Hu, G. C.; Ren, J. F.

2018-05-01

First principles calculations are used to study the spin polarization properties of benzene molecule adsorbed on the graphene surface which doped with transition metals including Mn, Cr, Fe, Co, and Ni. The densities of states (DOS) of the benzene molecule can be induced to be spin split at the Fermi level only when it is adsorbed on Mn-, and Cr-doped graphene. The p-orbital of the benzene molecule will interact with the d orbital of the doped atoms, which will generate new spin coupling states and lead to obvious spin polarization of the benzene molecule. The spin-polarized density distributions as well as the differential charge density distributions of the systems also suggest that Mn-doped graphene will induce bigger spin polarization than that of Cr-doped graphene. Benzene molecule could be spin-polarized when it is adsorbed on the graphene surface with transition metal dopants, which could be a new method for researching graphene-based organic spintronic devices.

Emergence of nontrivial magnetic excitations in a spin-liquid state of kagomé volborthite

PubMed Central

Watanabe, Daiki; Sugii, Kaori; Shimozawa, Masaaki; Suzuki, Yoshitaka; Yajima, Takeshi; Ishikawa, Hajime; Hiroi, Zenji; Shibauchi, Takasada; Matsuda, Yuji; Yamashita, Minoru

2016-01-01

When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly correlated spins fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here, we use thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report the observation of anomalous excitations that may unveil the unique features of the SL state. Our principal finding is a negative thermal Hall conductivity κxy which the charge-neutral spin excitations in a gapless SL state of the 2D kagomé insulator volborthite Cu3V2O7(OH)2⋅2H2O exhibit, in much the same way in which charged electrons show the conventional electric Hall effect. We find that κxy is absent in the high-temperature paramagnetic state and develops upon entering the SL state in accordance with the growth of the short-range spin correlations, demonstrating that κxy is a key signature of the elementary excitation formed in the SL state. These results suggest the emergence of nontrivial elementary excitations in the gapless SL state which feel the presence of fictitious magnetic flux, whose effective Lorentz force is found to be less than 1/100 of the force experienced by free electrons. PMID:27439874

Investigations of quantum pendulum dynamics in a spin-1 BEC

NASA Astrophysics Data System (ADS)

Hoang, Thai; Gerving, Corey; Land, Ben; Anquez, Martin; Hamley, Chris; Chapman, Michael

2013-05-01

We investigate the quantum spin dynamics of a spin-1 BEC initialized to an unstable critical point of the dynamical phase space. The subsequent evolution of the collective states of the system is analogous to an inverted simple pendulum in the quantum limit and yields non-classical states with quantum correlations. For short evolution times in the low depletion limit, we observe squeezed states and for longer times beyond the low depletion limit we observe highly non-Gaussian distributions. C.D. Hamley, C.S. Gerving, T.M. Hoang, E.M. Bookjans, and M.S. Chapman, ``Spin-Nematic Squeezed Vacuum in a Quantum Gas,'' Nature Physics 8, 305-308 (2012).

Role of Entropy and Structural Parameters in the Spin State Transition of LaCoO3

NASA Astrophysics Data System (ADS)

Chakrabarti, Bismayan; Birol, Turan; Haule, Kristjan

The spin state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge consistent Density Functional Theory + Dynamical Mean Field Theory (DFT+DMFT). We show, from first principles, that LaCoO3 cannot be described by a single, pure spin state at any temperature, but instead shows a gradual change in the population of higher spin multiples as temperature is increased. We explicitly elucidate the critical role of the lattice expansion and oxygen octahedral rotations in the spin state transition. We also show that the spin state transition and the metal-insulator transition in the compound occur at different temperatures. In addition, our results shed light on the importance of electronic entropy, which has so far been ignored in all first principles studies of this material.

Thermal imaging of spin Peltier effect

NASA Astrophysics Data System (ADS)

Daimon, Shunsuke; Iguchi, Ryo; Hioki, Tomosato; Saitoh, Eiji; Uchida, Ken-Ichi

2016-12-01

The Peltier effect modulates the temperature of a junction comprising two different conductors in response to charge currents across the junction, which is used in solid-state heat pumps and temperature controllers in electronics. Recently, in spintronics, a spin counterpart of the Peltier effect was observed. The `spin Peltier effect' modulates the temperature of a magnetic junction in response to spin currents. Here we report thermal imaging of the spin Peltier effect; using active thermography technique, we visualize the temperature modulation induced by spin currents injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of the metal/insulator interface. This finding allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is more than one order of magnitude greater than previously believed.

Distinction of nuclear spin states with the scanning tunneling microscope.

PubMed

Natterer, Fabian Donat; Patthey, François; Brune, Harald

2013-10-25

We demonstrate rotational excitation spectroscopy with the scanning tunneling microscope for physisorbed H(2) and its isotopes HD and D(2). The observed excitation energies are very close to the gas phase values and show the expected scaling with the moment of inertia. Since these energies are characteristic for the molecular nuclear spin states we are able to identify the para and ortho species of hydrogen and deuterium, respectively. We thereby demonstrate nuclear spin sensitivity with unprecedented spatial resolution.

Quantum correlation properties in Matrix Product States of finite-number spin rings

NASA Astrophysics Data System (ADS)

Zhu, Jing-Min; He, Qi-Kai

2018-02-01

The organization and structure of quantum correlation (QC) of quantum spin-chains are very rich and complex. Hence the depiction and measures about the QC of finite-number spin rings deserved to be investigated intensively by using Matrix Product States(MPSs) in addition to the case with infinite-number. Here the dependencies of the geometric quantum discord(GQD) of two spin blocks on the total spin number, the spacing spin number and the environment parameter are presented in detail. We also compare the GQD with the total correlation(TC) and the classical correlation(CC) and illustrate its characteristics. Predictably, our findings may provide the potential of designing the optimal QC experimental detection proposals and pave the way for the designation of optimal quantum information processing schemes.

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

NASA Astrophysics Data System (ADS)

Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst; Mahmoodian, Sahand; Löbl, Matthias Christian; Söllner, Immo; Schott, Rüdiger; Papon, Camille; Pregnolato, Tommaso; Stobbe, Søren; Midolo, Leonardo; Schröder, Tim; Wieck, Andreas Dirk; Ludwig, Arne; Warburton, Richard John; Lodahl, Peter

2018-05-01

The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin-photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates, single-photon transistors and the efficient generation of a photonic cluster state.

How to Calculate Spin-Spin Coupling and Spin-Rotation Coupling Strengths and Their Uncertainties from Spectroscopic Data: Application to the c(1^3Σ_g^+) State of Diatomic Lithium

NASA Astrophysics Data System (ADS)

Dattani, Nikesh S.; Li, Xuan

2013-06-01

Recent high-resolution (± 0.00002 cm^{-1}) photo-association spectroscopy (PAS) data of seven previously unexplored vibrational levels of the 1^3Σ_g^+ state of Li_2 have allowed for the first ever experimental determination of the spin-spin (λ_v) and spin-rotation (γ_v) coupling constants in a diatomic lithium system. For triplet states of diatomic molecules such as the 1^3Σ_g^+ state of Li_2, the three spin-spin/spin-rotation resolved energies associated with a ro-vibrational state |v,N> were expressed explicity in terms of B_v, λ_v, and γ_v in 1929 by Kramer's first-order formulas and then in 1937 by Schlapp's more refined formulas. Given spectroscopic data, while it has never been difficult to extract λ_v and γ_v from Schlapp's formulas, it has been a challenge to reliably predict how accurate these extracted values are. This is for two reasons: (1) the lack of a rigorous method to estimate the uncertainty in B_v, (2) the non-linearity of Schlapp's coupled equations has meant that traditionally they have had to be solved numerically by Newton iterations which makes error propagation difficult. The former challenge has been this year solved by Le Roy with a modification of Hutson's perturbation theory of, and the latter problem has now been solved by symbolic computing software that solves Schlapp's coupled non-linear equations analytically for the first time since their introduction in 1937. M. Semczuk, X. Li, W. Gunton, M. Haw, N. Dattani, J. Witz, A. Mills, D. Jones, K. Madison, Physical Review A {87}, XX (2013) H. Kramers, Zeitschrift fur Physik {53}, 422 (1929) R. Schlapp, Physical Review {51}, 342 (1937) J. Hutson, J. Phys. B, {14}, 851 (1981)

Experimental linear-optics simulation of ground-state of an Ising spin chain.

PubMed

Xue, Peng; Zhan, Xian; Bian, Zhihao

2017-05-19

We experimentally demonstrate a photonic quantum simulator: by using a two-spin Ising chain (an isolated dimer) as an example, we encode the wavefunction of the ground state with a pair of entangled photons. The effect of magnetic fields, leading to a critical modification of the correlation between two spins, can be simulated by just local operations. With the ratio of simulated magnetic fields and coupling strength increasing, the ground state of the system changes from a product state to an entangled state and back to another product state. The simulated ground states can be distinguished and the transformations between them can be observed by measuring correlations between photons. This simulation of the Ising model with linear quantum optics opens the door to the future studies which connect quantum information and condensed matter physics.

Bounds on the entanglement entropy of droplet states in the XXZ spin chain

NASA Astrophysics Data System (ADS)

Beaud, V.; Warzel, S.

2018-01-01

We consider a class of one-dimensional quantum spin systems on the finite lattice Λ ⊂Z , related to the XXZ spin chain in its Ising phase. It includes in particular the so-called droplet Hamiltonian. The entanglement entropy of energetically low-lying states over a bipartition Λ = B ∪ Bc is investigated and proven to satisfy a logarithmic bound in terms of min{n, |B|, |Bc|}, where n denotes the maximal number of down spins in the considered state. Upon addition of any (positive) random potential, the bound becomes uniformly constant on average, thereby establishing an area law. The proof is based on spectral methods: a deterministic bound on the local (many-body integrated) density of states is derived from an energetically motivated Combes-Thomas estimate.

Toroidal high-spin isomers in the nucleus 304120

NASA Astrophysics Data System (ADS)

Staszczak, A.; Wong, Cheuk-Yin; Kosior, A.

2017-05-01

Background: Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with I =Iz . The toroidal high-K isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. Purpose: We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus 120304184. Method: Our method consists of three steps: First, we use the deformation-constrained Skyrme-Hartree-Fock-Bogoliubov approach to search for the nuclear density distributions with toroidal shapes. Next, using these toroidal distributions as starting configurations, we apply an additional cranking constraint of a large angular momentum I =Iz about the symmetry z axis and search for the energy minima of the system as a function of the deformation. In the last step, if a local energy minimum with I =Iz is found, we perform at this point the cranked symmetry- and deformation-unconstrained Skyrme-Hartree-Fock calculations to locate a stable toroidal high-spin isomeric state in free convergence. Results: We have theoretically located two toroidal high-spin isomeric states of 120304184 with an angular momentum I =Iz=81 ℏ (proton 2p-2h, neutron 4p-4h excitation) and I =Iz=208 ℏ (proton 5p-5h, neutron 8p-8h) at the quadrupole moment deformations Q20=-297.7 b and Q20=-300.8 b with energies 79.2 and 101.6 MeV above the spherical ground state, respectively. The nuclear density distributions of the toroidal high-spin isomers 120304184(Iz=81 ℏ and 208 ℏ ) have the maximum density close to the nuclear matter density, 0.16 fm-3, and a torus major to minor radius aspect ratio R /d =3.25 . Conclusions: We demonstrate that aligned angular momenta of Iz=81 ℏ and 208 ℏ arising from

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.

High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb

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

Sirohi, Anshu; Saha, Preetha; Gayen, Sirshendu

CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number ofmore » measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high (∼47%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane are strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.« less

Cobalt spin states and hyperfine interactions in LaCoO3 investigated by LDA+U calculations

NASA Astrophysics Data System (ADS)

Hsu, Han; Blaha, Peter; Wentzcovitch, Renata M.; Leighton, C.

2010-09-01

With a series of local-density approximation plus Hubbard U calculations, we have demonstrated that for lanthanum cobaltite (LaCoO3) , the electric field gradient at the cobalt nucleus can be used as a fingerprint to identify the spin state of the cobalt ion. Therefore, in principle, the spin state of the cobalt ion can be unambiguously determined from nuclear magnetic resonance spectra. Our calculations also suggest that a crossover from the low-spin to intermediate-spin state in the temperature range of 0-90 K is unlikely, based on the half-metallic band structure associated with isolated IS Co ions, which is incompatible with the measured conductivity.

Direct comparison of current-induced spin polarization in topological insulator Bi2Se3 and InAs Rashba states

DOE PAGES

Li, C. H.; van ‘t Erve, O. M. J.; Rajput, S.; ...

2016-11-17

Three-dimensional topological insulators (TIs) exhibit time-reversal symmetry protected, linearly dispersing Dirac surface states with spin–momentum locking. Band bending at the TI surface may also lead to coexisting trivial two-dimensional electron gas (2DEG) states with parabolic energy dispersion. A bias current is expected to generate spin polarization in both systems, although with different magnitude and sign. Here we compare spin potentiometric measurements of bias current-generated spin polarization in Bi2Se3(111) where Dirac surface states coexist with trivial 2DEG states, and in InAs(001) where only trivial 2DEG states are present. We observe spin polarization arising from spin–momentum locking in both cases, with oppositemore » signs of the measured spin voltage. We present a model based on spin dependent electrochemical potentials to directly derive the sign expected for the Dirac surface states, and show that the dominant contribution to the current-generated spin polarization in the TI is from the Dirac surface states.« less

Two-nucleon high-spin states, the Bansal-French model and the crude shell model

NASA Astrophysics Data System (ADS)

Chan, Tsan Ung

1987-08-01

Recent data on two-nucleon stretched high-spin states agree well with the crude shell model predictions. For two-neutron high-spin states, the A and T linear dependence of B2n in the Bansal-French model can be deduced from the A and T linear dependence of Bn and the crude shell model. 7-2 states in some Zn and Ge even nuclei might be two-proton states. This hypothesis should be confirmed by two-proton transfer reaction.

High spin states in 164Lu

NASA Astrophysics Data System (ADS)

Juneja, P.; Gupta, S. L.; Pancholi, S. C.; Kumar, Ashok; Mehta, D.; Chaturvedi, L.; Katoch, S. K.; Malik, S.; Shanker, G.; Bhowmik, R. K.; Muralithar, S.; Rodrigues, G.; Singh, R. P.

1996-03-01

High spin states in the odd-odd 164Lu nucleus have been investigated for the first time, through in-beam gamma-ray spectroscopy, following the 150Sm(19F,5n) reaction at beam energy Elab=105 MeV. Four bands, including two signature split bands are identified. The interpretation of the experimental results is discussed in comparison with the existing data in the neighboring nuclei and in the framework of the cranked shell model. The πh11/2⊗νi13/2 yrast band exhibits anomalous signature splitting and signature inversion is observed at a spin of 18ħ. This provides the missing datum for the systematics of staggering and signature inversion for the neighboring odd-odd N=93 isotones and supports the predictions of angular-momentum projection calculations by Hara and Sun. In the second signature split πh 11/2h9/2 band, the AB neutron crossing occurs at a rotational frequency of ~0.29 MeV. This is indicative of the disappearance of the blocking effect of the odd neutron.

Spin Vector Distribution in the Koronis Family for a Sample Complete to IAU H=10.88

NASA Astrophysics Data System (ADS)

Slivan, Stephen M.; Hosek, Matt; Sokol, Alyssa; Maynard, Sarah; Payne, Anna; Radford, Arden; Springmann, Alessondra; Mailhot, Emily; Midkiff, Alan; Russell, April; Stephens, Robert D.

2016-10-01

Because they share the same formation age, asteroid family members have experienced similar evolution for similar lengths of time, offering valuable information to help understand spin evolution processes. Clustered distributions of spin vectors determined from observations of ten of the largest Koronis family members (Slivan 2002) revealed evidence of spin modification by YORP thermal radiation torques (Vokrouhlický et al. 2003). The currently known spin vector sample in the Koronis family (Slivan et al., 2003; Slivan et al., 2009, Hanuš et al., 2011; Hanuš et al., 2013; Durech et al., 2016) clearly shows the two spin groupings observed among the large members: (1) the larger group with low-obliquity retrograde spin and periods between about 3 h and 30 h, and (2) a smaller group with prograde spin obliquity near 45° and periods near 8 h, characteristic of trapping in the s6 spin-orbit resonance (Vokrouhlický et al. 2003). There's also one "stray" longer-period prograde object with smaller obliquity, perhaps trapped in some other resonance.A limitation of the existing spin vector sample, which (using IAU H as a proxy for size) includes 16 of the brightest 27 members of the family, is that selection biases render it complete only to the brightest 12 members. Slivan et al. (2008) began a lightcurve observing program to increase the sample of Koronis family spin vectors down to about 20 km diameter.We report pole solutions that were determined for fourteen survey objects using lightcurves recorded from 2005-2016, which complete the Koronis spin vector sample to the brightest 22 members, now including 24 of the brightest 27 members. The larger sample adds several objects to the existing group of low-obliquity retrograde rotators, increasing the period range upward to almost 60 h, and also identifies two companions for the stray longer-period prograde spin object, strengthening the case for the presence of a second cluster of objects trapped in a spin

Spin coherent-state path integrals and the instanton calculus

NASA Astrophysics Data System (ADS)

Garg, Anupam; Kochetov, Evgueny; Park, Kee-Su; Stone, Michael

2003-01-01

We use an instanton approximation to the continuous-time spin coherent-state path integral to obtain the tunnel splitting of classically degenerate ground states. We show that provided the fluctuation determinant is carefully evaluated, the path integral expression is accurate to order O(1/j). We apply the method to the LMG model and to the molecular magnet Fe8 in a transverse field.

Lifting SU(2) spin networks to projected spin networks

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

Dupuis, Maiete; Livine, Etera R.

2010-09-15

Projected spin network states are the canonical basis of quantum states of geometry for the recent EPRL-FK spinfoam models for quantum gravity introduced by Engle-Pereira-Rovelli-Livine and Freidel-Krasnov. They are functionals of both the Lorentz connection and the time-normal field. We analyze in detail the map from these projected spin networks to the standard SU(2) spin networks of loop quantum gravity. We show that this map is not one to one and that the corresponding ambiguity is parameterized by the Immirzi parameter. We conclude with a comparison of the scalar products between projected spin networks and SU(2) spin network states.

Tunnel junction of helical edge states: Determining and controlling spin-preserving and spin-flipping processes through transconductance

NASA Astrophysics Data System (ADS)

Sternativo, Pietro; Dolcini, Fabrizio

2014-01-01

When a constriction is realized in a 2D quantum spin Hall system, electron tunneling between helical edge states occurs via two types of channels allowed by time-reversal symmetry, namely spin-preserving (p) and spin-flipping (f) tunneling processes. Determining and controlling the effects of these two channels is crucial to the application of helical edge states in spintronics. We show that, despite that the Hamiltonian terms describing these two processes do not commute, the scattering matrix entries of the related 4-terminal setup always factorize into products of p-term and f-term contributions. Such factorization provides an operative way to determine the transmission coefficients Tp and Tf related to each of the two processes, via transconductance measurements. Furthermore, these transmission coefficients are also found to be controlled independently by a suitable combination of two gate voltages applied across the junction. This result holds for an arbitrary profile of the tunneling amplitudes, including disorder in the tunnel region, enabling us to discuss the effect of the finite length of the tunnel junction, and the space modulation of both magnitude and phase of the tunneling amplitudes.

Fact or factitious? A psychobiological study of authentic and simulated dissociative identity states.

PubMed

Reinders, A A T S; Reinders, A A T Simone; Willemsen, Antoon T M; Vos, Herry P J; den Boer, Johan A; Nijenhuis, Ellert R S

2012-01-01

Dissociative identity disorder (DID) is a disputed psychiatric disorder. Research findings and clinical observations suggest that DID involves an authentic mental disorder related to factors such as traumatization and disrupted attachment. A competing view indicates that DID is due to fantasy proneness, suggestibility, suggestion, and role-playing. Here we examine whether dissociative identity state-dependent psychobiological features in DID can be induced in high or low fantasy prone individuals by instructed and motivated role-playing, and suggestion. DID patients, high fantasy prone and low fantasy prone controls were studied in two different types of identity states (neutral and trauma-related) in an autobiographical memory script-driven (neutral or trauma-related) imagery paradigm. The controls were instructed to enact the two DID identity states. Twenty-nine subjects participated in the study: 11 patients with DID, 10 high fantasy prone DID simulating controls, and 8 low fantasy prone DID simulating controls. Autonomic and subjective reactions were obtained. Differences in psychophysiological and neural activation patterns were found between the DID patients and both high and low fantasy prone controls. That is, the identity states in DID were not convincingly enacted by DID simulating controls. Thus, important differences regarding regional cerebral bloodflow and psychophysiological responses for different types of identity states in patients with DID were upheld after controlling for DID simulation. The findings are at odds with the idea that differences among different types of dissociative identity states in DID can be explained by high fantasy proneness, motivated role-enactment, and suggestion. They indicate that DID does not have a sociocultural (e.g., iatrogenic) origin.

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.

Ground state and magnetic phase transitions of the spin Lieb nanolattice: Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Masrour, R.; Jabar, A.

2018-02-01

We study the ground state and magnetic properties of the spin Lieb nanolattice with three lattice sites with spins (S = 2 , σ = 1 / 2 , q = 3 / 2) using Monte Carlo simulations. The ground state phase diagrams of the Lieb nanolattice have been studied. The phase diagrams show some key features: coexistence between regions, points where six, eight and ten states can coexist. The total and partial magnetization of each sublattice is given and the corresponding magnetic susceptibility is also found. The variation of total magnetization with the exchange interaction RSq and Rσq of the Lieb nanolattice with three lattice sites with spins (S , σ , q) has been studied. Moreover, the total magnetization versus the fields Δ /JSσ of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are established for several values of Rσq and Rsq. Magnetic hysteresis cycles of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are found for several values of Rsq and temperature. We show that the superparamagnetism behaviour appears for a weak coupling value between S and q thus around the transition temperature.

Spin nematics next to spin singlets

NASA Astrophysics Data System (ADS)

Yokoyama, Yuto; Hotta, Chisa

2018-05-01

We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

Two-nucleon high-spin states, the Bansal-French model and the crude shell model

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

Chan, T.U.

Recent data on two-nucleon stretched high-spin states agree well with the crude shell model predictions. For two-neutron high-spin states, the A and T linear dependence of B/sub 2n/ in the Bansal-French model can be deduced from the A and T linear dependence of B/sub n/ and the crude shell model. 7/sub 2//sup -/ states in some Zn and Ge even nuclei might be two-proton states. This hypothesis should be confirmed by two-proton transfer reaction.

Short-range magentic correlations and dynamic orbital ordering in the thermally activated spin state of LaCoO3

NASA Astrophysics Data System (ADS)

Rosenkranz, S.; Phelan, D.; Louca, D.; Lee, S. H.; Chupas, P. J.; Osborn, R.; Zheng, H.; Mitchell, J. F.

2006-03-01

The cobalt perovskites La1-xSrxCoO3 show intriguing spin, lattice, and orbital properties similar to the ones observed in colossal magnetoresistive manganites. The x=0 parent compound is a non-magnetic insulator at low temperatures, but shows evidence of a spin-state transition of the cobalt ions above 50K from a low-spin to an intermediate or high-spin configuration. Using high resolution, inelastic neutron scattering, we observe a distinct low energy excitation at 0.6meV coincident with the thermally induced spin state transition observed in susceptibility measurements. The thermal activation of this excited spin state also leads to short-range, dynamic ferro- and antiferromagnetic correlations. These observations are consistent with the activation of a zero-field split intermediate spin state as well as the presence of dynamic orbital ordering of these excited states. Work supported by US DOE BES-DMS W-31-109-ENG-38 and NSF DMR-0454672

Single-copy entanglement in critical quantum spin chains

NASA Astrophysics Data System (ADS)

Eisert, J.; Cramer, M.

2005-10-01

We consider the single-copy entanglement as a quantity to assess quantum correlations in the ground state in quantum many-body systems. We show for a large class of models that already on the level of single specimens of spin chains, criticality is accompanied with the possibility of distilling a maximally entangled state of arbitrary dimension from a sufficiently large block deterministically, with local operations and classical communication. These analytical results—which refine previous results on the divergence of block entropy as the rate at which maximally entangled pairs can be distilled from many identically prepared chains—are made quantitative for general isotropic translationally invariant spin chains that can be mapped onto a quasifree fermionic system, and for the anisotropic XY model. For the XX model, we provide the asymptotic scaling of ˜(1/6)log2(L) , and contrast it with the block entropy.

Titan's Spin State from Cassini SAR Data: Evidence for an Internal Ocean

NASA Astrophysics Data System (ADS)

Stiles, B. W.; Lorenz, R. D.; Kirk, R. L.; Hensley, S.; Lee, E. M.; Allison, M. D.; Perci Del Marmo, P.; Lunine, J. I.; Ostro, S. J.; Gim, Y.; Hamilton, G. A.; Johnson, W. T.; West, R. D.

2007-12-01

Nineteen areas on Titan's surface have been imaged with Cassini SAR on two separate flybys with intervals from 2 months to 2 years. We have used the apparent misregistration of features between separate flybys (which is 10-30 km) to construct a refined model of Titan's spin state, estimating six parameters: pole right ascension and declination, spin rate, and these quantities' first time derivatives. Because we have only observed Titan for 2-3 years, our dataset is unlikely to be sensitive to higher order derivatives. We have studied the uncertainty and degree of correlation of the model parameters, and have also searched the parameter space to eliminate the possibility of more than one solution. Our model spin state differs significantly from both the zero-inclination synchronous model and from any other plausible Cassini state. The previously estimated pole location and spin rate used by the IAU and the Cassini mission definitely cannot account for the observed misregistration. Because our imaging resolution is between 300 m and 1 km, we are very sensitive to the pole location and spin rate. Our estimated corrections to the pole and spin rate exceed their corresponding standard errors by factors of 40 and 4, respectively. We examined 150 different features in 19 different twice-observed regions. Applying our pole correction reduces the feature misregistration from tens of km to 3-4 km. Applying the spin rate and derivative corrections further reduces the misregistration to 1-2 km. We propose that our result reflects coupling between atmospheric angular momentum changes and an internal water ocean, for two reasons. First, astrodynamical theory predicts that if Titan is in a dynamically relaxed Cassini state there is a relationship between the moment of inertia factor C/MR2 and the obliquity of a few tenths of a degree. Our results (from two independent analyses of the overlaps) show an appreciable deviation from the expected range of states: either Titan suffered

Ground-state phase diagram of an anisotropic spin-1/2 model on the triangular lattice

NASA Astrophysics Data System (ADS)

Luo, Qiang; Hu, Shijie; Xi, Bin; Zhao, Jize; Wang, Xiaoqun

2017-04-01

Motivated by a recent experiment on the rare-earth material YbMgGaO4 [Y. Li et al., Phys. Rev. Lett. 115, 167203 (2015), 10.1103/PhysRevLett.115.167203], which found that the ground state of YbMgGaO4 is a quantum spin liquid, we study the ground-state phase diagram of an anisotropic spin-1 /2 model that was proposed to describe YbMgGaO4. Using the density matrix renormalization-group method in combination with the exact-diagonalization method, we calculate a variety of physical quantities, including the ground-state energy, the fidelity, the entanglement entropy and spin-spin correlation functions. Our studies show that in the quantum phase diagram, there is a 120∘ phase and two distinct stripe phases. The transitions from the two stripe phases to the 120∘ phase are of the first order. However, the transition between the two stripe phases is not of the first order, which is different from its classical counterpart. Additionally, we find no evidence for a quantum spin liquid in this model. Our results suggest that additional terms may also be important to model the material YbMgGaO4. These findings will stimulate further experimental and theoretical works in understanding the quantum spin-liquid ground state in YbMgGaO4.

Collisional evolution of rotating, non-identical particles. [in Saturn rings

NASA Technical Reports Server (NTRS)

Salo, H.

1987-01-01

Hameen-Anttila's (1984) theory of self-gravitating collisional particle disks is extended to include the effects of particle spin. Equations are derived for the coupled evolution of random velocities and spins, showing that friction and surface irregularity both reduce the local velocity dispersion and transfer significant amounts of random kinetic energy to rotational energy. Results for the equilibrium ratio of rotational energy to random kinetic energy are exact not only for identical nongravitating mass points, but also if finite size, self-gravitating forces, or size distribution are included. The model is applied to the dynamics of Saturn's rings, showing that the inclusion of rotation reduces the geometrical thickness of the layer of cm-sized particles to, at most, about one-half, with large particles being less affected.

Spin-flavor structure of chiral-odd generalized parton distributions in the large- N c limit

DOE PAGES

Schweitzer, P.; Weiss, C.

2016-10-05

We study the spin-flavor structure of the nucleon's chiral-odd generalized parton distributions (transversity GPDs) in the large-N c limit of QCD. In contrast to the chiral-even case, only three combinations of the four chiral-odd GPDs are nonzero in the leading order of the 1/N c expansion: E-bar T = E T+2H-tilde T, H T, and E-tilde T. The degeneracy is explained by the absence of spin-orbit interactions correlating the transverse momentum transfer with the transverse quark spin. It can also be deduced from the natural N c scaling of the quark-nucleon helicity amplitudes associated with the GPDs. In the GPDmore » E-bar T the flavor-singlet component u+d is leading in the 1/N c expansion, while in H T and E-tilde T it is the flavor-nonsinglet components u–d. Furthermore, the large-N c relations are consistent with the spin-flavor structure extracted from hard exclusive π 0 and η electroproduction data, if it is assumed that the processes are mediated by twist-3 amplitudes involving the chiral-odd GPDs and the chiral-odd pseudoscalar meson distribution amplitudes.« less

Four-state non-volatile memory in a multiferroic spin filter tunnel junction

NASA Astrophysics Data System (ADS)

Ruan, Jieji; Li, Chen; Yuan, Zhoushen; Wang, Peng; Li, Aidong; Wu, Di

2016-12-01

We report a spin filter type multiferroic tunnel junction with a ferromagnetic/ferroelectric bilayer barrier. Memory functions of a spin filter magnetic tunnel junction and a ferroelectric tunnel junction are combined in this single device, producing four non-volatile resistive states that can be read out in a non-destructive manner. This concept is demonstrated in a LaNiO3/Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 all-oxide tunnel junction. The ferromagnetic insulator Pr0.8Ca0.2MnO3 serves as the spin filter and the ferromagnetic metal La0.7Sr0.3MnO3 is the spin analyzer. The ferroelectric polarization reversal in the BaTiO3 barrier switches the tunneling barrier height to produce a tunneling electroresistance. The ferroelectric switching also modulates the spin polarization and the spin filtering efficiency in Pr0.8Ca0.2MnO3.

Coherent Spin Control at the Quantum Level in an Ensemble-Based Optical Memory.

PubMed

Jobez, Pierre; Laplane, Cyril; Timoney, Nuala; Gisin, Nicolas; Ferrier, Alban; Goldner, Philippe; Afzelius, Mikael

2015-06-12

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies suggest this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here, we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read-out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.

Lower limits of spin detection efficiency for two-parameter two-qubit (TPTQ) states with non-ideal ferromagnetic detectors

NASA Astrophysics Data System (ADS)

Majd, Nayereh; Ghasemi, Zahra

2016-10-01

We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell's inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.

Spectral narrowing and spin echo for localized carriers with heavy-tailed L evy distribution of hopping times

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

Yue, Z.; Mkhitaryan, Vagharsh; Raikh, M. E.

2016-02-02

We study analytically the free induction decay and the spin echo decay originating from the localized carriers moving between the sites which host random magnetic fields. Due to disorder in the site positions and energies, the on-site residence times, , are widely spread according to the L evy distribution. The power-law tail ∝ τ -1-∝ in the distribution of does not affect the conventional spectral narrowing for α > 2, but leads to a dramatic acceleration of the free induction decay in the domain 2 > α > 1. The next abrupt acceleration of the decay takes place as becomesmore » smaller than 1. In the latter domain the decay does not follow a simple-exponent law. To capture the behavior of the average spin in this domain, we solve the evolution equation for the average spin using the approach different from the conventional approach based on the Laplace transform. Unlike the free induction decay, the tail in the distribution of the residence times leads to the slow decay of the spin echo. The echo is dominated by realizations of the carrier motion for which the number of sites, visited by the carrier, is minimal.« less

Self-organized critical behavior and marginality in Ising spin glasses

NASA Astrophysics Data System (ADS)

Sharma, Auditya; Yeo, Joonhyun; Moore, M. A.

2018-05-01

We have studied numerically the states reached in a quench from various temperatures in the one-dimensional fully-connected Kotliar, Anderson and Stein Ising spin glass model. This is a model where there are long-range interactions between the spins which falls off as a power σ of their separation. We have made a detailed study in particular of the energies of the states reached in a quench from infinite temperature and their overlaps, including the spin glass susceptibility. In the regime where , where the model is similar to the Sherrington–Kirkpatrick model, we find that the spin glass susceptibility diverges logarithmically with increasing N, the number of spins in the system, whereas for it remains finite. We attribute the behavior for to self-organized critical behavior, where the system after the quench is close to the transition between states which have trivial overlaps and those with the non-trivial overlaps associated with replica symmetry breaking. We have also found by studying the distribution of local fields that the states reached in the quench have marginal stability but only when .

Local-spin-density calculations for iron: Effect of spin interpolation on ground-state properties

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

MacLaren, J.M.; Clougherty, D.P.; Albers, R.C.

1990-08-15

Scalar-relativistic self-consistent linear muffin-tin orbital (LMTO) calculations for bcc and fcc Fe have been performed with several different local approximations to the exchange and correlation energy density and potential. Overall, in contrast to the conclusions of previous studies, we find that the local-spin-density approximation to exchange and correlation can provide an adequate description of bulk Fe {ital provided} that a proper parametrization of the correlation energy density and potential of the homogeneous electron gas over both spin and density is used. Lattice constants, found from the position of the minimum of the total energy as a function of Wigner-Seitz radius,more » agree to within 1% (for {ital s},{ital p},{ital d} LMTO's only) and within 1--2% (for {ital s},{ital p},{ital d},{ital f} LMTO's) of the experimental lattice constants for all forms used for the local correlation. The best agreement, however, was obtained using a local correlation potential derived from the Vosko-Wilk-Nusair form for the spin dependence of the correlation energy density. The calculation performed with this correlation potential was also the only calculation to correctly predict a bcc ferromagnetic ground state.« less

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation.

PubMed

Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T; Roy, Soumya Singha; Brown, Richard C D; Pileio, Giuseppe; Levitt, Malcolm H

2015-01-28

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in (13)CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.

Quasi-two-dimensional spin correlations in the triangular lattice bilayer spin glass LuCoGaO 4

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

Fritsch, Katharina; Ross, Kathyrn A.; Granroth, Garrett E.

Here we present a single-crystal time-of-flight neutron scattering study of the static and dynamic spin correlations in LuCoGaO 4, a quasi-two-dimensional dilute triangular lattice antiferromagnetic spin-glass material. This system is based on Co 2+ ions that are randomly distributed on triangular bilayers within the YbFe 2O 4 type, hexagonal crystal structure. Antiferromagnetic short-range two-dimensional correlations at wave vectors Q = (1/3,1/3, L) develop within the bilayers at temperatures as high as |Θ CW| ~100 K and extend over roughly five unit cells at temperatures below T g = 19 K. These two-dimensional static correlations are observed as diffuse rods ofmore » neutron scattering intensity along c * and display a continuous spin freezing process in their energy dependence. Aside from exhibiting these typical spin-glass characteristics, this insulating material reveals a novel gapped magnetic resonant spin excitation at ΔE ~12 meV localized around Q = (1 / 3, 1 / 3,L) . The temperature dependence of the spin gap associated with this two-dimensional excitation correlates with the evolution of the static correlations into the spin-glass state ground state. Lastly, we associate it with the effect of the staggered exchange field acting on the S eff = 1/2 Ising-like doublet of the Co 2+ moments.« less

Quasi-two-dimensional spin correlations in the triangular lattice bilayer spin glass LuCoGaO 4

DOE PAGES

Fritsch, Katharina; Ross, Kathyrn A.; Granroth, Garrett E.; ...

2017-09-13

Here we present a single-crystal time-of-flight neutron scattering study of the static and dynamic spin correlations in LuCoGaO 4, a quasi-two-dimensional dilute triangular lattice antiferromagnetic spin-glass material. This system is based on Co 2+ ions that are randomly distributed on triangular bilayers within the YbFe 2O 4 type, hexagonal crystal structure. Antiferromagnetic short-range two-dimensional correlations at wave vectors Q = (1/3,1/3, L) develop within the bilayers at temperatures as high as |Θ CW| ~100 K and extend over roughly five unit cells at temperatures below T g = 19 K. These two-dimensional static correlations are observed as diffuse rods ofmore » neutron scattering intensity along c * and display a continuous spin freezing process in their energy dependence. Aside from exhibiting these typical spin-glass characteristics, this insulating material reveals a novel gapped magnetic resonant spin excitation at ΔE ~12 meV localized around Q = (1 / 3, 1 / 3,L) . The temperature dependence of the spin gap associated with this two-dimensional excitation correlates with the evolution of the static correlations into the spin-glass state ground state. Lastly, we associate it with the effect of the staggered exchange field acting on the S eff = 1/2 Ising-like doublet of the Co 2+ moments.« less

Fact or Factitious? A Psychobiological Study of Authentic and Simulated Dissociative Identity States

PubMed Central

Simone Reinders, A. A. T.; Willemsen, Antoon T. M.; Vos, Herry P. J.; den Boer, Johan A.; Nijenhuis, Ellert R. S.

2012-01-01

Background Dissociative identity disorder (DID) is a disputed psychiatric disorder. Research findings and clinical observations suggest that DID involves an authentic mental disorder related to factors such as traumatization and disrupted attachment. A competing view indicates that DID is due to fantasy proneness, suggestibility, suggestion, and role-playing. Here we examine whether dissociative identity state-dependent psychobiological features in DID can be induced in high or low fantasy prone individuals by instructed and motivated role-playing, and suggestion. Methodology/Principal Findings DID patients, high fantasy prone and low fantasy prone controls were studied in two different types of identity states (neutral and trauma-related) in an autobiographical memory script-driven (neutral or trauma-related) imagery paradigm. The controls were instructed to enact the two DID identity states. Twenty-nine subjects participated in the study: 11 patients with DID, 10 high fantasy prone DID simulating controls, and 8 low fantasy prone DID simulating controls. Autonomic and subjective reactions were obtained. Differences in psychophysiological and neural activation patterns were found between the DID patients and both high and low fantasy prone controls. That is, the identity states in DID were not convincingly enacted by DID simulating controls. Thus, important differences regarding regional cerebral bloodflow and psychophysiological responses for different types of identity states in patients with DID were upheld after controlling for DID simulation. Conclusions/Significance The findings are at odds with the idea that differences among different types of dissociative identity states in DID can be explained by high fantasy proneness, motivated role-enactment, and suggestion. They indicate that DID does not have a sociocultural (e.g., iatrogenic) origin. PMID:22768068

Quantum spin transistor with a Heisenberg spin chain.

PubMed

Marchukov, O V; Volosniev, A G; Valiente, M; Petrosyan, D; Zinner, N T

2016-10-10

Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements.

Ground-state magnetization of the Ising spin glass: A recursive numerical method and Chen-Ma scaling

NASA Astrophysics Data System (ADS)

Sepehrinia, Reza; Chalangari, Fartash

2018-03-01

The ground-state properties of quasi-one-dimensional (Q1D) Ising spin glass are investigated using an exact numerical approach and analytical arguments. A set of coupled recursive equations for the ground-state energy are introduced and solved numerically. For various types of coupling distribution, we obtain accurate results for magnetization, particularly in the presence of a weak external magnetic field. We show that in the weak magnetic field limit, similar to the 1D model, magnetization exhibits a singular power-law behavior with divergent susceptibility. Remarkably, the spectrum of magnetic exponents is markedly different from that of the 1D system even in the case of two coupled chains. The magnetic exponent makes a crossover from being dependent on a distribution function to a constant value independent of distribution. We provide an analytic theory for these observations by extending the Chen-Ma argument to the Q1D case. We derive an analytical formula for the exponent which is in perfect agreement with the numerical results.

Liquid-state nuclear spin comagnetometers.

PubMed

Ledbetter, M P; Pustelny, S; Budker, D; Romalis, M V; Blanchard, J W; Pines, A

2012-06-15

We discuss nuclear spin comagnetometers based on ultralow-field nuclear magnetic resonance in mixtures of miscible solvents, each rich in a different nuclear spin. In one version thereof, Larmor precession of protons and 19F nuclei in a mixture of thermally polarized pentane and hexafluorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fluctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5×10(-9)  Hz, or about 5×10(-11)  Hz in ≈1 day of integration. In a second version, spin precession of protons and 129Xe nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed.

Spin-valley locking in the normal state of a transition-metal dichalcogenide superconductor.

PubMed

Bawden, L; Cooil, S P; Mazzola, F; Riley, J M; Collins-McIntyre, L J; Sunko, V; Hunvik, K W B; Leandersson, M; Polley, C M; Balasubramanian, T; Kim, T K; Hoesch, M; Wells, J W; Balakrishnan, G; Bahramy, M S; King, P D C

2016-05-23

Metallic transition-metal dichalcogenides (TMDCs) are benchmark systems for studying and controlling intertwined electronic orders in solids, with superconductivity developing from a charge-density wave state. The interplay between such phases is thought to play a critical role in the unconventional superconductivity of cuprates, Fe-based and heavy-fermion systems, yet even for the more moderately-correlated TMDCs, their nature and origins have proved controversial. Here, we study a prototypical example, 2H-NbSe2, by spin- and angle-resolved photoemission and first-principles theory. We find that the normal state, from which its hallmark collective phases emerge, is characterized by quasiparticles whose spin is locked to their valley pseudospin. This results from a combination of strong spin-orbit interactions and local inversion symmetry breaking, while interlayer coupling further drives a rich three-dimensional momentum dependence of the underlying Fermi-surface spin texture. These findings necessitate a re-investigation of the nature of charge order and superconducting pairing in NbSe2 and related TMDCs.

Spin correlations in the {Lambda}{Lambda} and {Lambda}{Lambda}-bar systems generated in relativistic heavy-ion collisions

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

Lyuboshitz, V. L.; Lyuboshitz, V. V., E-mail: Valery.Lyuboshitz@jinr.r

2010-05-15

Spin correlations for the {Lambda}{Lambda} and {Lambda}{Lambda}-bar pairs, generated in relativistic heavy-ion collisions, and related angular correlations at the joint registration of hadronic decays of two hyperons, in which space parity is not conserved, are analyzed. The correlation tensor components can be derived from the double angular distribution of products of two decays by the method of 'moments'. The properties of the 'trace' of the correlation tensor (a sum of three diagonal components), determining the relative fractions of the triplet states and singlet state of respective pairs, are discussed. Spin correlations for two identical particles ({Lambda}{Lambda}) and two nonidentical particlesmore » ({Lambda}{Lambda}-bar) are considered from the viewpoint of the conventional model of one-particle sources. In the framework of this model, correlations vanish at sufficiently large relative momenta. However, under these conditions, in the case of two nonidentical particles ({Lambda}{Lambda}-bar) a noticeable role is played by two-particle annihilation (two-quark, two-gluon) sources, which lead to the difference of the correlation tensor from zero. In particular, such a situation may arise when the system passes through the 'mixed phase.'« less

Spin glass behavior in frustrated quantum spin system CuAl 2 O 4 with a possible orbital liquid state

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

Nirmala, R.; Jang, Kwang-Hyun; Sim, Hasung

2017-02-15

CuAl 2O 4 is a normal spinel oxide having quantum spin, S = 1/2 for Cu 2+. It is a rather unique feature that the Cu 2+ ions of CuAl 2O 4 sit at a tetrahedral position, not like the usual octahedral position for many oxides. At low temperatures, it exhibits all the thermodynamic evidence of a quantum spin glass. For example, the polycrystalline CuAl 2O 4 shows a cusp centered at ~2 K in the low-field dc magnetization data and a clear frequency dependence in the ac magnetic susceptibility while it displays logarithmic relaxation behavior in a time dependencemore » of the magnetization. At the same time, there is a peak at ~2.3 K in the heat capacity, which shifts towards a higher temperature with magnetic fields. Conversely, there is no evidence of new superlattice peaks in the high-resolution neutron powder diffraction data when cooled from 40 to 0.4 K. This implies that there is no long-ranged magnetic order down to 0.4 K, thus confirming a spin glass-like ground state for CuAl 2O 4. Interestingly, there is no sign of structural distortion either although Cu 2+ is a Jahn–Teller active ion. Therefore, we claim that an orbital liquid state is the most likely ground state in CuAl 2O 4. Of further interest, it also exhibits a large frustration parameter, f = |θ CW/T m| ~ 67, one of the largest values reported for spinel oxides. These observations suggest that CuAl 2O 4 should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.« less

Global potential energy surface of ground state singlet spin O4

NASA Astrophysics Data System (ADS)

Mankodi, Tapan K.; Bhandarkar, Upendra V.; Puranik, Bhalchandra P.

2018-02-01

A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2-O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.

Spin-imbalanced pairing and Fermi surface deformation in flat bands

NASA Astrophysics Data System (ADS)

Huhtinen, Kukka-Emilia; Tylutki, Marek; Kumar, Pramod; Vanhala, Tuomas I.; Peotta, Sebastiano; Törmä, Päivi

2018-06-01

We study the attractive Hubbard model with spin imbalance on two lattices featuring a flat band: the Lieb and kagome lattices. We present mean-field phase diagrams featuring exotic superfluid phases, similar to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, whose stability is confirmed by dynamical mean-field theory. The nature of the pairing is found to be richer than just the Fermi surface shift responsible for the usual FFLO state. The presence of a flat band allows for changes in the particle momentum distributions at null energy cost. This facilitates formation of nontrivial superfluid phases via multiband Cooper pair formation: the momentum distribution of the spin component in the flat band deforms to mimic the Fermi surface of the other spin component residing in a dispersive band. The Fermi surface of the unpaired particles that are typical for gapless superfluids becomes deformed as well. The results highlight the profound effect of flat dispersions on Fermi surface instabilities, and provide a potential route for observing spin-imbalanced superfluidity and superconductivity.

Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution

DOE PAGES

Zhang, Wenkai; Kjaer, Kasper S.; Alonso-Mori, Roberto; ...

2016-08-25

Developing light-harvesting and photocatalytic molecules made with iron could provide a cost effective, scalable, and environmentally benign path for solar energy conversion. To date these developments have been limited by the sub-picosecond metal-to-ligand charge transfer (MLCT) electronic excited state lifetime of iron based complexes due to spin crossover – the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand iron complexes with four cyanide (CN –) ligands and one 2,2'-bipyridine (bpy) ligand. This enablesmore » MLCT excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL) Kβ hard X-ray fluorescence spectroscopy with femtosecond time-resolved UV-visible absorption spectroscopy to characterize the electronic excited state dynamics initiated by MLCT excitation of [Fe(CN) 4(bpy)] 2–. The two experimental techniques are highly complementary; the time-resolved UV-visible measurement probes allowed electronic transitions between valence states making it sensitive to ligand-centered electronic states such as MLCT states, whereas the Kβ fluorescence spectroscopy provides a sensitive measure of changes in the Fe spin state characteristic of metal-centered excited states. Here, we conclude that the MLCT excited state of [Fe(CN) 4(bpy)] 2– decays with roughly a 20 ps lifetime without undergoing spin crossover, exceeding the MLCT excited state lifetime of [Fe(2,2'-bipyridine) 3] 2+ by more than two orders of magnitude.« less

Competing Spin Liquids and Hidden Spin-Nematic Order in Spin Ice with Frustrated Transverse Exchange

NASA Astrophysics Data System (ADS)

Taillefumier, Mathieu; Benton, Owen; Yan, Han; Jaubert, L. D. C.; Shannon, Nic

2017-10-01

Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho2 Ti2 O7 and Dy2 Ti2 O7 exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related "quantum spin-ice" materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

Ultrafast optical control of individual quantum dot spin qubits.

PubMed

De Greve, Kristiaan; Press, David; McMahon, Peter L; Yamamoto, Yoshihisa

2013-09-01

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a 'flying' photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers. This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin-spin entanglement can be generated if each spin can emit a photon that is entangled

Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb2Se3

NASA Astrophysics Data System (ADS)

Das, Shekhar; Sirohi, Anshu; Kumar Gupta, Gaurav; Kamboj, Suman; Vasdev, Aastha; Gayen, Sirshendu; Guptasarma, Prasenjit; Das, Tanmoy; Sheet, Goutam

2018-06-01

Majority of the A2B3 -type chalcogenide systems with strong spin-orbit coupling (SOC), such as Bi2Se3,Bi2Te3 , and Sb2Te3 , etc., are topological insulators. One important exception is Sb2Se3 where a topological nontrivial phase was argued to be possible under ambient conditions, but such a phase could be detected to exist only under pressure. In this paper, we show that Sb2Se3 like Bi2Se3 displays a generation of highly spin-polarized current under mesoscopic superconducting point contacts as measured by point-contact Andreev reflection spectroscopy. In addition, we observe a large negative and anisotropic magnetoresistance of the mesoscopic metallic point contacts formed on Sb2Se3 . Our band-structure calculations confirm the trivial nature of Sb2Se3 crystals and reveal two trivial surface states one of which shows large spin splitting due to Rashba-type SOC. The observed high spin polarization and related phenomena in Sb2Se3 can be attributed to this spin splitting.

Coexistence of long-range cycloidal order and spin-cluster glass state in the multiferroic BaYFeO4.

PubMed

Ghara, Somnath; Sundaresan, A

2018-06-20

We report the presence of spin glass state below the cycloidal spin ordering in the multiferroic BaYFeO 4 . This compound is known to crystallize in an orthorhombic structure with a centrosymmetric space group Pnma and exhibits two successive antiferromagnetic phase transitions. Upon cooling, it undergoes a spin density wave (SDW)-like antiferromagnetic ordering at T N1 ~ 48 K and a cycloidal ordering at T N2 ~ 35 K. Using dc magnetic memory effect and magnetization relaxation studies, we have shown that this oxide undergoes a reentrant spin glass transition below T * ~ 17 K. Our analysis suggests the presence of spin clusters in the glassy state. The coexistence of spin-cluster glass and long-range cycloidal ordered states results in an exchange bias effect at 2 K. The origin of the glassy state has been attributed to freezing of some Fe 3+ moments, which do not participate in the long-range ordering.

Coexistence of long-range cycloidal order and spin-cluster glass state in the multiferroic BaYFeO4

NASA Astrophysics Data System (ADS)

Ghara, Somnath; Sundaresan, A.

2018-06-01

We report the presence of spin glass state below the cycloidal spin ordering in the multiferroic BaYFeO4. This compound is known to crystallize in an orthorhombic structure with a centrosymmetric space group Pnma and exhibits two successive antiferromagnetic phase transitions. Upon cooling, it undergoes a spin density wave (SDW)-like antiferromagnetic ordering at T N1 ~ 48 K and a cycloidal ordering at T N2 ~ 35 K. Using dc magnetic memory effect and magnetization relaxation studies, we have shown that this oxide undergoes a reentrant spin glass transition below T * ~ 17 K. Our analysis suggests the presence of spin clusters in the glassy state. The coexistence of spin-cluster glass and long-range cycloidal ordered states results in an exchange bias effect at 2 K. The origin of the glassy state has been attributed to freezing of some Fe3+ moments, which do not participate in the long-range ordering.

Generation of large scale GHZ states with the interactions of photons and quantum-dot spins

NASA Astrophysics Data System (ADS)

Miao, Chun; Fang, Shu-Dong; Dong, Ping; Yang, Ming; Cao, Zhuo-Liang

2018-03-01

We present a deterministic scheme for generating large scale GHZ states in a cavity-quantum dot system. A singly charged quantum dot is embedded in a double-sided optical microcavity with partially reflective top and bottom mirrors. The GHZ-type Bell spin state can be created and two n-spin GHZ states can be perfectly fused to a 2n-spin GHZ state with the help of n ancilla single-photon pulses. The implementation of the current scheme only depends on the photon detection and its need not to operate multi-qubit gates and multi-qubit measurements. Discussions about the effect of the cavity loss, side leakage and exciton cavity coupling strength for the fidelity of generated states show that the fidelity can remain high enough by controlling system parameters. So the current scheme is simple and feasible in experiment.

Unravelling the spin-state of solvated [Fe(bpp)2]2+ spin-crossover complexes: structure-function relationship.

PubMed

Giménez-López, Maria Del Carmen; Clemente-León, Miguel; Giménez-Saiz, Carlos

2018-05-23

This paper reports firstly the syntheses, crystal structures, and thermal and magnetic properties of spin crossover salts of formulae [Fe(bpp)2]3[Cr(CN)6]2·13H2O (1) and [Fe(bpp)2][N(CN)2]2·H2O (2) (bpp = 2,6-bis(pyrazol-3-yl)pyridine) exhibiting hydrogen-bonded networks of low-spin [Fe(bpp)2]2+ complexes and [Cr(CN)6]3- or [N(CN)2]- anions, with solvent molecules located in the voids. Desolvation of 1 is accompanied by a complete low-spin (LS) to a high-spin (HS) transformation that becomes reversible after rehydration by exposing the sample to the humidity of air. The influence of the lattice water on the magnetic properties of spin-crossover [Fe(bpp)2]X2 complex salts has been documented. In most cases, it stabilises the LS state over the HS one. In other cases, it is rather the contrary. The second part of this paper is devoted to unravelling the reasons why the lattice solvent stabilises one form over the other through magneto-structural correlations of [Fe(bpp)2]2+ salts bearing anions with different charge/size ratios (Xn-). The [Fe(bpp)2]2+ stacking explaining these two different behaviours is correlated here with the composition of the second coordination sphere of the Fe centers and the ability of these anions to form hydrogen bonds and/or π-π stacking interactions between them or the bpp ligand.

Cooling a Mechanical Resonator with Nitrogen-Vacancy Centres Using a Room Temperature Excited State Spin-Strain Interaction

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

MacQuarrie, E. R.; Otten, M.; Gray, S. K.

Cooling a mechanical resonator mode to a sub-thermal state has been a long-standing challenge in physics. This pursuit has recently found traction in the field of optomechanics in which a mechanical mode is coupled to an optical cavity. An alternate method is to couple the resonator to a well-controlled two-level system. Here we propose a protocol to dissipatively cool a room temperature mechanical resonator using a nitrogen-vacancy centre ensemble. The spin ensemble is coupled to the resonator through its orbitally-averaged excited state, which has a spin-strain interaction that has not been previously studied. We experimentally demonstrate that the spin-strain couplingmore » in the excited state is 13.5 ± 0.5 times stronger than the ground state spin-strain coupling. Lastly, we then theoretically show that this interaction, combined with a high-density spin ensemble, enables the cooling of a mechanical resonator from room temperature to a fraction of its thermal phonon occupancy.« less

Cooling a Mechanical Resonator with Nitrogen-Vacancy Centres Using a Room Temperature Excited State Spin-Strain Interaction

DOE PAGES

MacQuarrie, E. R.; Otten, M.; Gray, S. K.; ...

2017-02-06

Cooling a mechanical resonator mode to a sub-thermal state has been a long-standing challenge in physics. This pursuit has recently found traction in the field of optomechanics in which a mechanical mode is coupled to an optical cavity. An alternate method is to couple the resonator to a well-controlled two-level system. Here we propose a protocol to dissipatively cool a room temperature mechanical resonator using a nitrogen-vacancy centre ensemble. The spin ensemble is coupled to the resonator through its orbitally-averaged excited state, which has a spin-strain interaction that has not been previously studied. We experimentally demonstrate that the spin-strain couplingmore » in the excited state is 13.5 ± 0.5 times stronger than the ground state spin-strain coupling. Lastly, we then theoretically show that this interaction, combined with a high-density spin ensemble, enables the cooling of a mechanical resonator from room temperature to a fraction of its thermal phonon occupancy.« less

Spin State of Co3+ Ions in Layered GdBaCo2O5.5 Cobaltite in the Paramagnetic Phase

NASA Astrophysics Data System (ADS)

Solin, N. I.; Naumov, S. V.; Telegin, S. V.

2018-04-01

A new scheme interpreting the changes in the spin state of Co3+ ions in GdBaCo2O5.5 in the course of the metal-insulator transition is proposed. The transition occurs gradually within a wide ( 100 K) temperature range. The changes in the spin state of Co3+ ions are revealed using the data on the linear thermal expansion. In the metallic state, less than one-half of Co3+ ions are in the high-spin (HS, S = 2) state in octahedra, whereas the remaining ions are in the low-spin (LS, S = 0) state. The transition to the nonmetallic state occurs owing to the transformation of the HS state to the LS state in octahedra and to the transformation of some part of LS Co3+ in pyramids to the intermediate-spin (IS, S = 1) state.

Distribution of blocking temperatures in nano-oxide layers of specular spin valves

NASA Astrophysics Data System (ADS)

Ventura, J.; Araujo, J. P.; Sousa, J. B.; Veloso, A.; Freitas, P. P.

2007-06-01

Specular spin valves show enhanced giant magnetoresistive (GMR) ratio when compared to other, simpler, spin valve structures. The enhancement of GMR results from specular reflection in nano-oxide layers (NOLs) formed by the partial oxidation of the pinned and free layer. These oxides forming the NOL order antiferromagnetically (AFM) below a temperature T ˜175 K. Here, we study the effects of the pinned layer magnetization and its domain structure on the AFM ordering of the NOL by performing field cooling measurements with different cooling fields (H0). We observe enhanced (reduced) exchange field and magnetoresistive ratio for H0>0(<0), i.e., parallel (antiparallel) to the pinned magnetization. These measurements allowed us to confirm the existence of a wide distribution of blocking temperatures (TB) in the NOL of specular spin valves, having a maximum at T ≈175 K, and extending to NOL regions with TB as low as 15 K.

Spin-dependent analysis of two-dimensional electron liquids

NASA Astrophysics Data System (ADS)

Bulutay, C.; Tanatar, B.

2002-05-01

Two-dimensional electron liquid (2D EL) at full Fermi degeneracy is revisited, giving special attention to the spin-polarization effects. First, we extend the recently proposed classical-map hypernetted-chain (CHNC) technique to the 2D EL, while preserving the simplicity of the original proposal. An efficient implementation of CHNC is given utilizing Lado's quadrature expressions for the isotropic Fourier transforms. Our results indicate that the paramagnetic phase stays to be the ground state until the Wigner crystallization density, even though the energy separation with the ferromagnetic and other partially polarized states become minute. We analyze compressibility and spin stiffness variations with respect to density and spin polarization, the latter being overlooked until now. Spin-dependent static structure factor and pair-distribution functions are computed; agreement with the available quantum Monte Carlo data persists even in the strong-coupling regime of the 2D EL.

Quantum spin transistor with a Heisenberg spin chain

PubMed Central

Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.

2016-01-01

Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements. PMID:27721438

Bound States and Field-Polarized Haldane Modes in a Quantum Spin Ladder.

PubMed

Ward, S; Mena, M; Bouillot, P; Kollath, C; Giamarchi, T; Schmidt, K P; Normand, B; Krämer, K W; Biner, D; Bewley, R; Guidi, T; Boehm, M; McMorrow, D F; Rüegg, Ch

2017-04-28

The challenge of one-dimensional systems is to understand their physics beyond the level of known elementary excitations. By high-resolution neutron spectroscopy in a quantum spin-ladder material, we probe the leading multiparticle excitation by characterizing the two-magnon bound state at zero field. By applying high magnetic fields, we create and select the singlet (longitudinal) and triplet (transverse) excitations of the fully spin-polarized ladder, which have not been observed previously and are close analogs of the modes anticipated in a polarized Haldane chain. Theoretical modeling of the dynamical response demonstrates our complete quantitative understanding of these states.

Engineering On-Surface Spin Crossover: Spin-State Switching in a Self-Assembled Film of Vacuum-Sublimable Functional Molecule.

PubMed

Kumar, Kuppusamy Senthil; Studniarek, Michał; Heinrich, Benoît; Arabski, Jacek; Schmerber, Guy; Bowen, Martin; Boukari, Samy; Beaurepaire, Eric; Dreiser, Jan; Ruben, Mario

2018-03-01

The realization of spin-crossover (SCO)-based applications requires study of the spin-state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface-bound thin molecular film is either quenched or heavily altered due to: (i) molecule-surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self-assembly strategy is proposed to fabricate thin spin-switchable surface-bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H 2 B(pz) 2 ) 2 (bpy)] (pz = pyrazole, bpy = 2,2'-bipyridine) with a dodecyl (C 12 ) alkyl chain yields a classical amphiphile-like functional and vacuum-sublimable charge-neutral Fe II complex, [Fe(H 2 B(pz) 2 ) 2 (C 12 -bpy)] (C 12 -bpy = dodecyl[2,2'-bipyridine]-5-carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiO x surfaces of the complex show comparable spin-state switching characteristics mediated by similar lamellar bilayer like self-assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO-based applications, especially in molecular spintronics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin squeezing as an indicator of quantum chaos in the Dicke model.

PubMed

Song, Lijun; Yan, Dong; Ma, Jian; Wang, Xiaoguang

2009-04-01

We study spin squeezing, an intrinsic quantum property, in the Dicke model without the rotating-wave approximation. We show that the spin squeezing can reveal the underlying chaotic and regular structures in phase space given by a Poincaré section, namely, it acts as an indicator of quantum chaos. Spin squeezing vanishes after a very short time for an initial coherent state centered in a chaotic region, whereas it persists over a longer time for the coherent state centered in a regular region of the phase space. We also study the distribution of the mean spin directions when quantum dynamics takes place. Finally, we discuss relations among spin squeezing, bosonic quadrature squeezing, and two-qubit entanglement in the dynamical processes.

Impurity-induced tuning of quantum-well States in spin-dependent resonant tunneling.

PubMed

Kalitsov, Alan; Coho, A; Kioussis, Nicholas; Vedyayev, Anatoly; Chshiev, M; Granovsky, A

2004-07-23

We report exact model calculations of the spin-dependent tunneling in double magnetic tunnel junctions in the presence of impurities in the well. We show that the impurity can tune selectively the spin channels giving rise to a wide variety of interesting and novel transport phenomena. The tunneling magnetoresistance, the spin polarization, and the local current can be dramatically enhanced or suppressed by impurities. The underlying mechanism is the impurity-induced shift of the quantum well states (QWSs), which depends on the impurity potential, impurity position, and the symmetry of the QWS. Copyright 2004 The American Physical Society

Defect states and their energetic position and distribution in organic molecular semiconductors

NASA Astrophysics Data System (ADS)

Sharma, Akanksha; Yadav, Sarita; Kumar, Pramod; Ray Chaudhuri, Sumita; Ghosh, Subhasis

2013-04-01

Energetic position and distribution of defect states due to structural disorder in pentacene and copper phthalocyanine have been obtained by capacitance based spectroscopic techniques. It has been shown that capacitance-frequency and capacitance-voltage characteristics exhibit Gaussian distribution of traps with an energetic position at around 0.5 eV above the highest occupied molecular orbital level of the pentacene and CuPc. These traps have been created by varying growth conditions and almost identical trap parameters in pentacene and copper phthalocyanine indicate that similar structural disorder is responsible for these traps.

Generation of Quality Pulses for Control of Qubit/Quantum Memory Spin States: Experimental and Simulation

DTIC Science & Technology

2016-09-01

TECHNICAL REPORT 3046 September 2016 GENERATION OF QUALITY PULSES FOR CONTROL OF QUBIT/QUANTUM MEMORY SPIN STATES: EXPERIMENTAL AND SIMULATION...control circuitry for control of electron/ nuclear spin states of qubits/quantum memory applicable to semiconductor, superconductor, ionic, and...coherence time of the qubit/ memory , we present as an example the integration of cryogenic superconductor components, including filters and

Multiple stable states of a periodically driven electron spin in a quantum dot using circularly polarized light

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2011-06-01

The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. The same physics underlie the frequency-locking effect for two-color and mode-locked excitations. However, the pulsed excitation with mode-locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than 100 stable channels.

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.

New low-spin states of 122Xe observed via high-statistics β-decay of 122Cs

NASA Astrophysics Data System (ADS)

Jigmeddorj, B.; Garrett, P. E.; Andreoiu, C.; Ball, G. C.; Bruhn, T.; Cross, D. S.; Garnsworthy, A. B.; Hadinia, B.; Moukaddam, M.; Park, J.; Pore, J. L.; Radich, A. J.; Rajabali, M. M.; Rand, E. T.; Rizwan, U.; Svensson, C. E.; Voss, P.; Wang, Z. M.; Wood, J. L.; Yates, S. W.

2018-05-01

Excited states of 122Xe were studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. Compton-suppressed HPGe detectors were used for measurements of γ-ray intensities, γγ coincidences, and γ-γ angular correlations. Two sets of data were collected to optimize the decays of the ground (21.2 s) and isomeric (3.7 min) states of 122Cs. The data collected have enabled the observation of about 505 new transitions and about 250 new levels, including 51 new low-spin states. Spin assignments have been made for 58 low-spin states based on the deduced β-decay feeding and γ-γ angular correlation analyses.

Optical implementation of spin squeezing

NASA Astrophysics Data System (ADS)

Ono, Takafumi; Sabines-Chesterking, Javier; Cable, Hugo; O'Brien, Jeremy L.; Matthews, Jonathan C. F.

2017-05-01

Quantum metrology enables estimation of optical phase shifts with precision beyond the shot-noise limit. One way to exceed this limit is to use squeezed states, where the quantum noise of one observable is reduced at the expense of increased quantum noise for its complementary partner. Because shot-noise limits the phase sensitivity of all classical states, reduced noise in the average value for the observable being measured allows for improved phase sensitivity. However, additional phase sensitivity can be achieved using phase estimation strategies that account for the full distribution of measurement outcomes. Here we experimentally investigate a model of optical spin-squeezing, which uses post-selection and photon subtraction from the state generated using a parametric downconversion photon source, and we investigate the phase sensitivity of this model. The Fisher information for all photon-number outcomes shows it is possible to obtain a quantum advantage of 1.58 compared to the shot-noise value for five-photon events, even though due to experimental imperfection, the average noise for the relevant spin-observable does not achieve sub-shot-noise precision. Our demonstration implies improved performance of spin squeezing for applications to quantum metrology.

Emergent Chiral Spin State in the Mott Phase of a Bosonic Kane-Mele-Hubbard Model

NASA Astrophysics Data System (ADS)

Plekhanov, Kirill; Vasić, Ivana; Petrescu, Alexandru; Nirwan, Rajbir; Roux, Guillaume; Hofstetter, Walter; Le Hur, Karyn

2018-04-01

Recently, the frustrated X Y model for spins 1 /2 on the honeycomb lattice has attracted a lot of attention in relation with the possibility to realize a chiral spin liquid state. This model is relevant to the physics of some quantum magnets. Using the flexibility of ultracold atom setups, we propose an alternative way to realize this model through the Mott regime of the bosonic Kane-Mele-Hubbard model. The phase diagram of this model is derived using bosonic dynamical mean-field theory. Focusing on the Mott phase, we investigate its magnetic properties as a function of frustration. We do find an emergent chiral spin state in the intermediate frustration regime. Using exact diagonalization we study more closely the physics of the effective frustrated X Y model and the properties of the chiral spin state. This gapped phase displays a chiral order, breaking time-reversal and parity symmetry, but is not topologically ordered (the Chern number is zero).

Isolation of EPR spectra and estimation of spin-states in two-component mixtures of paramagnets.

PubMed

Chabbra, Sonia; Smith, David M; Bode, Bela E

2018-04-26

The presence of multiple paramagnetic species can lead to overlapping electron paramagnetic resonance (EPR) signals. This complication can be a critical obstacle for the use of EPR to unravel mechanisms and aid the understanding of earth abundant metal catalysis. Furthermore, redox or spin-crossover processes can result in the simultaneous presence of metal centres in different oxidation or spin states. In this contribution, pulse EPR experiments on model systems containing discrete mixtures of Cr(i) and Cr(iii) or Cu(ii) and Mn(ii) complexes demonstrate the feasibility of the separation of the EPR spectra of these species by inversion recovery filters and the identification of the relevant spin states by transient nutation experiments. We demonstrate the isolation of component spectra and identification of spin states in a mixture of catalyst precursors. The usefulness of the approach is emphasised by monitoring the fate of the chromium species upon activation of an industrially used precatalyst system.

Electric-field induced spin accumulation in the Landau level states of topological insulator thin films

NASA Astrophysics Data System (ADS)

Siu, Zhuo Bin; Chowdhury, Debashree; Basu, Banasri; Jalil, Mansoor B. A.

2017-08-01

A topological insulator (TI) thin film differs from the more typically studied thick TI system in that the former has both a top and a bottom surface where the states localized at both surfaces can couple to one other across the finite thickness. An out-of-plane magnetic field leads to the formation of discrete Landau level states in the system, whereas an in-plane magnetization breaks the angular momentum symmetry of the system. In this work, we study the spin accumulation induced by the application of an in-plane electric field to the TI thin film system where the Landau level states and inter-surface coupling are simultaneously present. We show, via Kubo formula calculations, that the in-plane spin accumulation perpendicular to the magnetization due to the electric field vanishes for a TI thin film with symmetric top and bottom surfaces. A finite in-plane spin accumulation perpendicular to both the electric field and magnetization emerges upon applying either a differential magnetization coupling or a potential difference between the two film surfaces. This spin accumulation results from the breaking of the antisymmetry of the spin accumulation around the k-space equal-energy contours.

Spin-orbit coupling controlled ground state in Sr 2 ScOsO 6

DOE PAGES

Taylor, A. E.; Morrow, R.; Fishman, R. S.; ...

2016-06-27

In this paper, we report neutron scattering experiments which reveal a large spin gap in the magnetic excitation spectrum of weakly-monoclinic double perovskite Sr 2ScOsO 6. The spin gap is demonstrative of appreciable spin-orbit-induced anisotropy, despite nominally orbitally-quenched 5d 3Os 5+ ions. The system is successfully modeled including nearest neighbor interactions in a Heisenberg Hamiltonian with exchange anisotropy. We find that the presence of the spin-orbit-induced anisotropy is essential for the realization of the type I antiferromagnetic ground state. Finally, this demonstrates that physics beyond the LS or JJ coupling limits plays an active role in determining the collective propertiesmore » of 4d 3 and 5d 3 systems and that theoretical treatments must include spin-orbit coupling.« less

Spin-orbit coupling controlled ground state in Sr 2 ScOsO 6

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

Taylor, A. E.; Morrow, R.; Fishman, R. S.

In this paper, we report neutron scattering experiments which reveal a large spin gap in the magnetic excitation spectrum of weakly-monoclinic double perovskite Sr 2ScOsO 6. The spin gap is demonstrative of appreciable spin-orbit-induced anisotropy, despite nominally orbitally-quenched 5d 3Os 5+ ions. The system is successfully modeled including nearest neighbor interactions in a Heisenberg Hamiltonian with exchange anisotropy. We find that the presence of the spin-orbit-induced anisotropy is essential for the realization of the type I antiferromagnetic ground state. Finally, this demonstrates that physics beyond the LS or JJ coupling limits plays an active role in determining the collective propertiesmore » of 4d 3 and 5d 3 systems and that theoretical treatments must include spin-orbit coupling.« less

Effect of hyperfine-induced spin mixing on the defect-enabled spin blockade and spin filtering in GaNAs

NASA Astrophysics Data System (ADS)

Puttisong, Y.; Wang, X. J.; Buyanova, I. A.; Chen, W. M.

2013-03-01

The effect of hyperfine interaction (HFI) on the recently discovered room-temperature defect-enabled spin-filtering effect in GaNAs alloys is investigated both experimentally and theoretically based on a spin Hamiltonian analysis. We provide direct experimental evidence that the HFI between the electron and nuclear spin of the central Ga atom of the spin-filtering defect, namely, the Gai interstitials, causes strong mixing of the electron spin states of the defect, thereby degrading the efficiency of the spin-filtering effect. We also show that the HFI-induced spin mixing can be suppressed by an application of a longitudinal magnetic field such that the electronic Zeeman interaction overcomes the HFI, leading to well-defined electron spin states beneficial to the spin-filtering effect. The results provide a guideline for further optimization of the defect-engineered spin-filtering effect.

Quantum entropy and uncertainty for two-mode squeezed, coherent and intelligent spin states

NASA Technical Reports Server (NTRS)

Aragone, C.; Mundarain, D.

1993-01-01

We compute the quantum entropy for monomode and two-mode systems set in squeezed states. Thereafter, the quantum entropy is also calculated for angular momentum algebra when the system is either in a coherent or in an intelligent spin state. These values are compared with the corresponding values of the respective uncertainties. In general, quantum entropies and uncertainties have the same minimum and maximum points. However, for coherent and intelligent spin states, it is found that some minima for the quantum entropy turn out to be uncertainty maxima. We feel that the quantum entropy we use provides the right answer, since it is given in an essentially unique way.

Decoherence and Noise in Spin-based Solid State Quantum Computers. Approximation-Free Numerical Simulations

DTIC Science & Technology

2007-07-21

the spin coherent states P-representation", Conference on Quantum Computations and Many- Body Systems, February 2006, Key West, FL 9. B. N. Harmon...solid-state spin-based qubit systems was the focus of our project. Since decoherence is a complex many- body non-equilibrium process, and its...representation of the density matrix, see Sec. 3 below). This work prompted J. Taylor from the experimental group of C. Marcus and M. Lukin (funded by

Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

DOE PAGES

Kim, J. -W.; Choi, Y.; Chun, S. H.; ...

2018-03-26

Here, the combination of strong electron correlations in 3d transition metal oxides and spin-orbit interactions in the 5d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIrO 3 (SIO) and La 2/3Sr 1/3MnO 3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolvedmore » x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular-orbitals between the Mn and Ir layers modifying the Ir 5d electronic configuration through the mixture of t 2g and e g states, resulting in a deviation from J eff = ½. This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5d states with 2-dimensional 3d spin-polarized electrons through heterostructure design.« less

Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

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

Kim, J. -W.; Choi, Y.; Chun, S. H.

Here, the combination of strong electron correlations in 3d transition metal oxides and spin-orbit interactions in the 5d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIrO 3 (SIO) and La 2/3Sr 1/3MnO 3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolvedmore » x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular-orbitals between the Mn and Ir layers modifying the Ir 5d electronic configuration through the mixture of t 2g and e g states, resulting in a deviation from J eff = ½. This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5d states with 2-dimensional 3d spin-polarized electrons through heterostructure design.« less

Controlling entangled spin-orbit coupling of 5 d states with interfacial heterostructure engineering

NASA Astrophysics Data System (ADS)

Kim, J.-W.; Choi, Y.; Chun, S. H.; Haskel, D.; Yi, D.; Ramesh, R.; Liu, J.; Ryan, P. J.

2018-03-01

The combination of strong electron correlations in 3 d transition-metal oxides and spin-orbit interactions in the 5 d counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between SrIr O3 (SIO) and L a2 /3S r1 /3Mn O3 (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolved x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular orbitals between the Mn and Ir layers modifying the Ir 5 d electronic configuration through the mixture of t2 g and eg states, resulting in a deviation from Jeff=1 /2 . This result demonstrates a pathway to manipulate the spin-orbit entanglement in 5 d states with two-dimensional 3 d spin-polarized electrons through heterostructure design.

Equation-of-motion coupled-cluster method for ionised states with spin-orbit coupling using open-shell reference wavefunction

NASA Astrophysics Data System (ADS)

Wang, Zhifan; Wang, Fan

2018-04-01

The equation-of-motion coupled-cluster method for ionised states at the singles and doubles level (EOM-IP-CCSD) with spin-orbit coupling (SOC) included in post-Hartree-Fock (HF) steps is extended to spatially non-degenerate open-shell systems such as high spin states of s1, p3, σ1 or π2 configuration in this work. Pseudopotentials are employed to treat relativistic effects and spin-unrestricted scalar relativistic HF determinant is adopted as reference in calculations. Symmetry is not exploited in the implementation since both time-reversal and spatial symmetry is broken due to SOC. IPs with the EOM-IP-CCSD approach are those from the 3Σ1- states for high spin state of π2 configuration, while the ground state is the 3Σ0- state. When removing an electron from the high spin state of p3 configuration, only the 3P2 state can be reached. The open-shell EOM-IP-CCSD approach with SOC was employed in calculating IPs of some open-shell atoms with s1 configuration, diatomic molecules with π2 configuration and SOC splitting of the ionised π1 state, as well as IPs of VA atoms with p3 configuration. Our results demonstrate that this approach can be applied to ionised states of spatially non-degenerate open-shell states containing heavy elements with reasonable accuracy.

Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

PubMed Central

Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

2016-01-01

The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ∼80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg∼1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity. PMID:27187067

Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

NASA Astrophysics Data System (ADS)

Lingos, P. C.; Wang, J.; Perakis, I. E.

2015-05-01

Femtosecond (fs) coherent control of collective order parameters is important for nonequilibrium phase dynamics in correlated materials. Here, we propose such control of ferromagnetic order based on using nonadiabatic optical manipulation of electron-hole (e -h ) photoexcitations to create fs carrier-spin pulses with controllable direction and time profile. These spin pulses are generated due to the time-reversal symmetry breaking arising from nonperturbative spin-orbit and magnetic exchange couplings of coherent photocarriers. By tuning the nonthermal populations of exchange-split, spin-orbit-coupled semiconductor band states, we can excite fs spin-orbit torques that control complex magnetization pathways between multiple magnetic memory states. We calculate the laser-induced fs magnetic anisotropy in the time domain by using density matrix equations of motion rather than the quasiequilibrium free energy. By comparing to pump-probe experiments, we identify a "sudden" out-of-plane magnetization canting displaying fs magnetic hysteresis, which agrees with switchings measured by the static Hall magnetoresistivity. This fs transverse spin-canting switches direction with magnetic state and laser frequency, which distinguishes it from the longitudinal nonlinear optical and demagnetization effects. We propose that sequences of clockwise or counterclockwise fs spin-orbit torques, photoexcited by shaping two-color laser-pulse sequences analogous to multidimensional nuclear magnetic resonance (NMR) spectroscopy, can be used to timely suppress or enhance magnetic ringing and switching rotation in magnetic memories.

Arterial spin labeled perfusion imaging using three-dimensional turbo spin echo with a distributed spiral-in/out trajectory.

PubMed

Li, Zhiqiang; Schär, Michael; Wang, Dinghui; Zwart, Nicholas R; Madhuranthakam, Ananth J; Karis, John P; Pipe, James G

2016-01-01

The three-dimensional (3D) spiral turbo spin echo (TSE) sequence is one of the preferred readout methods for arterial spin labeled (ASL) perfusion imaging. Conventional spiral TSE collects the data using a spiral-out readout on a stack of spirals trajectory. However, it may result in suboptimal image quality and is not flexible in protocol design. The goal of this study is to provide a more robust readout technique without such limitation. The proposed technique incorporates a spiral-in/out readout into 3D TSE, and collects the data on a distributed spirals trajectory. The data set is split into the spiral-in and -out subsets that are reconstructed separately and combined after image deblurring. The volunteer results acquired with the proposed technique show no geometric distortion or signal pileup, as is present with GRASE, and no signal loss, as is seen with conventional spiral TSE. Examples also demonstrate the flexibility in changing the imaging parameters to satisfy various criteria. The 3D TSE with a distributed spiral-in/out trajectory provides a robust readout technique and allows for easy protocol design, thus is a promising alternative to GRASE or conventional spiral TSE for ASL perfusion imaging. © 2015 Wiley Periodicals, Inc.

Spin-resolved electron waiting times in a quantum-dot spin valve

NASA Astrophysics Data System (ADS)

Tang, Gaomin; Xu, Fuming; Mi, Shuo; Wang, Jian

2018-04-01

We study the electronic waiting-time distributions (WTDs) in a noninteracting quantum-dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using the scattering matrix approach. Since the quantum-dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD, and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin-transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first-passage time distributions to quantitatively characterize the spin-flip process. We observe that influence degree versus spin-transfer torque for different noncollinear angles as well as different polarizations collapse into a single curve showing universal behaviors. This demonstrates that cross-channel WTDs can be a pathway to characterize spin correlation in spintronics system.

A homonuclear spin-pair filter for solid-state NMR based on adiabatic-passage techniques

NASA Astrophysics Data System (ADS)

Verel, René; Baldus, Marc; Ernst, Matthias; Meier, Beat H.

1998-05-01

A filtering scheme for the selection of spin pairs (and larger spin clusters) under fast magic-angle spinning is proposed. The scheme exploits the avoided level crossing in spin pairs during an adiabatic amplitude sweep through the so-called HORROR recoupling condition. The advantages over presently used double-quantum filters are twofold. (i) The maximum theoretical filter efficiency is, due to the adiabatic variation, 100% instead of 73% as for transient methods. (ii) Since the filter does not rely on the phase-cycling properties of the double-quantum coherence, there is no need to obtain the full double-quantum intensity for all spins in the sample at one single point in time. The only important requirement is that all coupled spins pass through a two-spin state during the amplitude sweep. This makes the pulse scheme robust with respect to rf-amplitude missetting, rf-field inhomogeneity and chemical-shift offset.

Low temperature Schottky anomalies in the specific heat of LaCoO3: Defect-stabilized finite spin states

NASA Astrophysics Data System (ADS)

He, C.; Zheng, H.; Mitchell, J. F.; Foo, M. L.; Cava, R. J.; Leighton, C.

2009-03-01

Measurement of the low temperature specific heat of LaCoO3 single crystals reveals a previously unobserved Schottky anomaly with an energy level splitting, 0.5 meV, that is associated with the first excited spin state of the Co3+ ion. These states persist well below 2 K and have a g-factor around 3.5, consistent with the high-spin spin-orbit triplet, implying the existence of a low density (approximately 0.1% of the sites) of finite-spin Co ions even in the T =0 limit. We propose that these states are trapped at defects and are consistent with the magnetic excitons observed in earlier work.

Evidence for a temperature-induced spin-state transition of Co3+ in La2-xSrxCoO4

NASA Astrophysics Data System (ADS)

Hollmann, N.; Haverkort, M. W.; Benomar, M.; Cwik, M.; Braden, M.; Lorenz, T.

2011-05-01

We study the magnetic susceptibility of mixed-valent La2-xSrxCoO4 single crystals in the doping range of 0.5⩽x⩽0.8 for temperatures up to 1000 K. The magnetism below room temperature is described by paramagnetic Co2+ in the high-spin state and by Co3+ in the nonmagnetic low-spin state. At high temperatures, an increase in susceptibility is seen, which we attribute to a temperature-induced spin-state transition of Co3+. The susceptibility is analyzed by comparison to full-multiplet calculations for the thermal population of the high- and intermediate-spin states of Co3+.

Spin cat state generation for quadrupolar nuclei in semiconductor quantum dots or defect centers

NASA Astrophysics Data System (ADS)

Bulutay, Ceyhun

Implementing spin-based quantum information encoding schemes in semiconductors has a high priority. The so-called cat codes offer a paradigm that enables hardware-efficient error correction. Their inauguration to semiconductor-based nuclear magnetic resonance framework hinges upon the realization of coherent spin states (CSS). In this work, we show how the crucial superpositions of CSS can be generated for the nuclear spins. This is through the intrinsic electric quadrupole interaction involving a critical role by the biaxiality term that is readily available, as in strained heterostructures of semiconductors, or defect centers having nearby quadrupolar spins. The persistence of the cat states is achieved using a rotation pulse so as to harness the underlying fixed points of the classical Hamiltonian. We classify the two distinct types as polar- and equator-bound over the Bloch sphere with respect to principal axes. Their optimal performance as well as sensitivity under numerous parameter deviations are analyzed. Finally, we present how these modulo-2 cat states can be extended to modulo-4 by a three-pulse scheme. This work was supported by TUBITAK, The Scientific and Technological Research Council of Turkey through the project No. 114F409.

Spin Self-Rephasing and Very Long Coherence Times in a Trapped Atomic Ensemble

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

Deutsch, C.; Reinhard, F.; Schneider, T.

2010-07-09

We perform Ramsey spectroscopy on the ground state of ultracold {sup 87}Rb atoms magnetically trapped on a chip in the Knudsen regime. Field inhomogeneities over the sample should limit the 1/e contrast decay time to about 3 s, while decay times of 58{+-}12 s are actually observed. We explain this surprising result by a spin self-rephasing mechanism induced by the identical spin rotation effect originating from particle indistinguishability. We propose a theory of this synchronization mechanism and obtain good agreement with the experimental observations. The effect is general and may appear in other physical systems.

Spin-orbit-coupled Fermi gases of two-electron ytterbium atoms

NASA Astrophysics Data System (ADS)

He, Chengdong; Song, Bo; Haciyev, Elnur; Ren, Zejian; Seo, Bojeong; Zhang, Shanchao; Liu, Xiong-Jun; Jo, Gyu-Boong

2017-04-01

Spin-orbit coupling (SOC) has been realized in bosonic and fermionic atomic gases opening an avenue to novel physics associated with spin-momentum locking. In this talk, we will demonstrate all-optical method coupling two hyperfine ground states of 173Yb fermions through a narrow optical transition 1S0 -> 3P1. An optical AC Stark shift is applied to split the ground hyperfine levels and separate out an effective spin-1/2 subspace from other spin states for the realization of SOC. The spin dephasing dynamics and the asymmetric momentum distribution of the spin-orbit coupled Fermi gas are observed as a hallmark of SOC. The implementation of all-optical SOC for ytterbium fermions should offer a new route to a long-lived spin-orbit coupled Fermi gas and greatly expand our capability in studying novel spin-orbit physics with alkaline-earth-like atoms. Other ongoing experimental works related to SOC will be also discussed. Funded by Croucher Foundation and Research Grants Council (RGC) of Hong Kong (Project ECS26300014, GRF16300215, GRF16311516, and Croucher Innovation Grants); MOST (Grant No. 2016YFA0301604) and NSFC (No. 11574008).

Designing exotic many-body states of atomic spin and motion in photonic crystals.

PubMed

Manzoni, Marco T; Mathey, Ludwig; Chang, Darrick E

2017-03-08

Cold atoms coupled to photonic crystals constitute an exciting platform for exploring quantum many-body physics. For example, such systems offer the potential to realize strong photon-mediated forces between atoms, which depend on the atomic internal (spin) states, and where both the motional and spin degrees of freedom can exhibit long coherence times. An intriguing question then is whether exotic phases could arise, wherein crystalline or other spatial patterns and spin correlations are fundamentally tied together, an effect that is atypical in condensed matter systems. Here, we analyse one realistic model Hamiltonian in detail. We show that this previously unexplored system exhibits a rich phase diagram of emergent orders, including spatially dimerized spin-entangled pairs, a fluid of composite particles comprised of joint spin-phonon excitations, phonon-induced Néel ordering, and a fractional magnetization plateau associated with trimer formation.

Computing distance distributions from dipolar evolution data with overtones: RIDME spectroscopy with Gd(iii)-based spin labels.

PubMed

Keller, Katharina; Mertens, Valerie; Qi, Mian; Nalepa, Anna I; Godt, Adelheid; Savitsky, Anton; Jeschke, Gunnar; Yulikov, Maxim

2017-07-21

Extraction of distance distributions between high-spin paramagnetic centers from relaxation induced dipolar modulation enhancement (RIDME) data is affected by the presence of overtones of dipolar frequencies. As previously proposed, we account for these overtones by using a modified kernel function in Tikhonov regularization analysis. This paper analyzes the performance of such an approach on a series of model compounds with the Gd(iii)-PyMTA complex serving as paramagnetic high-spin label. We describe the calibration of the overtone coefficients for the RIDME kernel, demonstrate the accuracy of distance distributions obtained with this approach, and show that for our series of Gd-rulers RIDME technique provides more accurate distance distributions than Gd(iii)-Gd(iii) double electron-electron resonance (DEER). The analysis of RIDME data including harmonic overtones can be performed using the MATLAB-based program OvertoneAnalysis, which is available as open-source software from the web page of ETH Zurich. This approach opens a perspective for the routine use of the RIDME technique with high-spin labels in structural biology and structural studies of other soft matter.

Generation of Quality Pulses for Control of Qubit/Quantum Memory Spin States: Experimental and Simulation

DTIC Science & Technology

2016-09-01

TECHNICAL REPORT 3046 September 2016 GENERATION OF QUALITY PULSES FOR CONTROL OF QUBIT/QUANTUM MEMORY SPIN STATES: EXPERIMENTAL AND SIMULATION...nuclear spin states of qubits/quantum memory applicable to semiconductor, superconductor, ionic, and superconductor-ionic hybrid technologies. As the...pulse quality and need for development of single pulses with very high quality will impact directly the coherence time of the qubit/ memory , we present

Effect of spin fluctuations on the electronic structure in iron-based superconductors

NASA Astrophysics Data System (ADS)

Heimes, Andreas; Grein, Roland; Eschrig, Matthias

2012-08-01

Magnetic inelastic neutron scattering studies of iron-based superconductors reveal a strongly temperature-dependent spin-fluctuation spectrum in the normal conducting state, which develops a prominent low-energy resonance feature when entering the superconducting state. Angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS) allow us to study the fingerprints of fluctuation modes via their interactions with electronic quasiparticles. We calculate such fingerprints in 122 iron pnictides using an experimentally motivated spin-fluctuation spectrum and make a number of predictions that can be tested in ARPES and STS experiments. This includes discussions of the quasiparticle scattering rate and the superconducting order parameter. In quantitative agreement with experiment we reproduce the quasiparticle dispersions obtained from momentum distribution curves as well as energy distribution curves. We discuss the relevance of the coupling between spin fluctuations and electronic excitations for the superconducting mechanism.

Toroidal high-spin isomers in the nucleus 120 304

DOE PAGES

Staszczak, A.; Wong, Cheuk-Yin; Kosior, A.

2017-05-22

Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis withmore » $$I=I_{z}$$. The toroidal high-$K$ isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus $$^{304}{120}_{184}$$. This method consists of three steps: first, we use the deformation-constrained Skyrme-Hartree-Fock-Bogoliubov approach to search for the nuclear density distributions with toroidal shapes. Next, using these toroidal distributions as starting configurations we apply an additional cranking constraint of a large angular momentum $$I=I_{z}$$ about the symmetry $z$-axis and search for the energy minima of the system as a function of the deformation. In the last step, if a local energy minimum with $$I=I_{z}$$ is found, we perform at this point the cranked symmetry- and deformation-unconstrained Skyrme-Hartree-Fock calculations to locate a stable toroidal high-spin isomeric state in free convergence. Furthemore, we have theoretically located two toroidal high-spin isomeric states of $$^{304}{120}_{184}$$ with an angular momentum $I$=$$I_z$$=81$$\\hbar$$ (proton 2p-2h, neutron 4p-4h excitation) and $I$=$$I_z$$=208$$\\hbar$$ (proton 5p-5h, neutron 8p-8h) at the quadrupole moment deformations $$Q_{20}=-297.7$$~b and $$Q_{20}=-300.8$$~b with energies 79.2 MeV and 101.6 MeV above the spherical ground state, respectively. The nuclear density distributions of the toroidal high-spin isomers $$^{304}{120}_{184}(I_z$$=81$$\\hbar$$ and 208$$\\hbar$$) have the maximum density close to the nuclear matter density, 0.16 fm$$^{-3}$$, and a torus major to minor radius aspect ratio $R/d=3

Effect of site disorder on the ground state of a frustrated spin dimer quantum magnet

NASA Astrophysics Data System (ADS)

Hristov, Alexander; Shapiro, Maxwell; Lee, Minseong; Rodenbach, Linsey; Choi, Eun Sang; Park, Ju-Hyun; Munsie, Tim; Luke, Graeme; Fisher, Ian

Ba3Mn2O8 is a geometrically frustrated spin dimer quantum magnet. Pairs of Mn 5+ (S = 1) ions are strongly coupled via antiferromagnetic exchange to yield a singlet ground state, with excited triplet and quintuplet states. Isovalent substitution of V5+ (S = 0) for Mn breaks dimers, resulting in unpaired S = 1 spins, the ground state of which is investigated here for compositions spanning the range 0 <= x <= 1 of Ba3(Mn1-xVx)2O8. From a theoretical perspective, for dimers occupying an unfrustrated bipartite lattice, such site disorder is anticipated to yield long range magnetism for unpaired Mn spins both in the dilute limit where x is small, a phenomena known as order-by-disorder, and in the proximity of x = 1 / 2 where the system is maximally disordered and close to a percolation threshold. In this frustrated system, however, our experiments find evidence of spin freezing for six compositions 0 . 05 <= x <= 0 . 85 . In this regime, we find entropy removed at an energy scale independent of the freezing temperature. We discuss the possibility of a spin-glass to random singlet transition for critical compositions in the two dilute limits x -> 0 and x -> 1 . NSF DMR-Award 1205165.

Enhanced spin Seebeck effect signal due to spin-momentum locked topological surface states

DOE PAGES

Jiang, Zilong; Chang, Cui -Zu; Masir, Massoud Ramezani; ...

2016-05-04

Spin-momentum locking in protected surface states enables efficient electrical detection of magnon decay at a magnetic-insulator/topological-insulator heterojunction. Here we demonstrate this property using the spin Seebeck effect (SSE), that is, measuring the transverse thermoelectric response to a temperature gradient across a thin film of yttrium iron garnet, an insulating ferrimagnet, and forming a heterojunction with (Bi xSb 1–x) 2Te 3, a topological insulator. The non-equilibrium magnon population established at the interface can decay in part by interactions of magnons with electrons near the Fermi energy of the topological insulator. When this decay channel is made active by tuning (Bi xSbmore » 1–x) 2Te 3 into a bulk insulator, a large electromotive force emerges in the direction perpendicular to the in-plane magnetization of yttrium iron garnet. Lastly, the enhanced, tunable SSE which occurs when the Fermi level lies in the bulk gap offers unique advantages over the usual SSE in metals and therefore opens up exciting possibilities in spintronics.« less

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.

Spin-state polarons as a precursor to ferromagnetism and metallicity in hole-doped LaCoO3

NASA Astrophysics Data System (ADS)

Podlesnyak, A.; Russina, M.; Pomjakushina, E.; Conder, K.; Khomskii, D.

2008-03-01

Lightly doped cobaltites La1-xSrxCoO3 exhibit magnetic properties at low temperatures, in strong contrast to the diamagnetic LaCoO3. We undertook an inelastic neutron scattering study with the goal to identify the energy spectrum and magnetic state of cobalt ions in the doped system with x=0.002. In distinguish to the parent compound, where no excitations have been found for T<30 K, an inelastic peak at δE ˜0.75 meV was observed in La0.998Sr0.002CoO3 at T=1.5 K. The intensity of this excitation is much higher than what is expected from an estimated concentration of doped holes. Furthermore, strong Zeeman splitting of the inelastic peak corresponds to an unusually high effective magnetic moment ˜15 μB. Neighboring low-spin (LS) Co^4+ and intermediate-spin Co^3+ ions can share an eg electron by swapping configuration. The t2g electrons, in their turn, couple ferromagnetically. Therefore, we propose that the holes introduced in the LS state of LaCoO3 are extended over the neighboring Co sites forming spin-state polarons and transforming the involved Co^3+ ions to the higher spin state. Grows of spin-state polarons with hole doping finally results in a metallic ferromagnetic state for x > 0.3.

The Excited Spin State of 1I/2017 U1 ‘Oumuamua

NASA Astrophysics Data System (ADS)

Belton, Michael J. S.; Hainaut, Olivier R.; Meech, Karen J.; Mueller, Beatrice E. A.; Kleyna, Jan T.; Weaver, Harold A.; Buie, Marc W.; Drahus, Michał; Guzik, Piotr; Wainscoat, Richard J.; Waniak, Wacław; Handzlik, Barbara; Kurowski, Sebastian; Xu, Siyi; Sheppard, Scott S.; Micheli, Marco; Ebeling, Harald; Keane, Jacqueline V.

2018-04-01

We show that ‘Oumuamua’s excited spin could be in a high-energy long axis mode (LAM) state, which implies that its shape could be far from the highly elongated shape found in previous studies. CLEAN and ANOVA algorithms are used to analyze ‘Oumuamua’s lightcurve using 818 observations over 29.3 days. Two fundamental periodicities are found at frequencies (2.77 ± 0.11) and (6.42 ± 0.18) cycles/day, corresponding to (8.67 ± 0.34) hr and (3.74 ± 0.11) hr, respectively. The phased data show that the lightcurve does not repeat in a simple manner, but approximately shows a double minimum at 2.77 cycles/day and a single minimum at 6.42 cycles/day. ‘Oumuamua could be spinning in either the LAM or short axis mode (SAM). For both, the long axis precesses around the total angular momentum vector with an average period of (8.67 ± 0.34) hr. For the three LAMs we have found, the possible rotation periods around the long axis are 6.58, 13.15, or 54.48 hr, with 54.48 hr being the most likely. ‘Oumuamua may also be nutating with respective periods of half of these values. We have also found two possible SAM states where ‘Oumuamua oscillates around the long axis with possible periods at 13.15 and 54.48 hr. In this case any nutation occurs with the same periods. Determination of the spin state, the amplitude of the nutation, the direction of the total angular momentum vector (TAMV), and the average total spin period may be possible with a direct model fit to the lightcurve. We find that ‘Oumuamua is “cigar-shaped,” if close to its lowest rotational energy, and an extremely oblate spheroid if close to its highest energy state.

A new DFT functional based on spin-states and SN2 barriers

NASA Astrophysics Data System (ADS)

Swart, M.; Solà, M.; Bickelhaupt, F. M.

2012-12-01

We recently reported a study into what causes the dramatic differences between OPBE and PBE for reaction barriers, spin-state energies, hydrogen-bonding and π-π stacking energies.1 It was achieved by smoothly switching from OPBE to PBE at a predefined point P of the reduced density gradient s. By letting the point P run as function of the reduced density gradient s, with values from s=0.1 to s=10, we could determine which part of the exchange functional determines its behavior for the different interactions. Based on the thus obtained results, we created a new exchange functional that showed the good results of OPBE for reaction barriers and spin-state energies, and combined it with the good (H-bonds) and reasonable (π-stacking) results of PBE for weak interactions. In other words, it combined the best of OPBE with the best of PBE. Encouraged by these good results, we have further improved the new exchange functional and fine-tuned its parameters.2 Similar to the switched functional from ref. 1, our new SSB functional2 works well for SN2 barriers (see e.g. ref. 3), spin states and H-bonding interactions. Moreover, by including Grimme's dispersion corrections4,5 (to give our final SSB-D functional) it also works well for π-π stacking interactions.2 In summary, we have constructed a new GGA exchange functional that when combined with the sPBE correlation functional6 gives the correct spin ground-state of iron complexes, and small deviations for SN2 barriers (2.7 kcalṡmol-1), geometries (0.005 Å), Hbond distances (0.012 Å), weak interactions (S22 set, 0.5 kcalṡmol-1), and transition-metal ligand distances (0.008 Å).

Spin liquid state in the disordered triangular lattice Sc 2Ga 2CuO 7 revealed by NMR

DOE PAGES

Khuntia, P.; Kumar, R.; Mahajan, A. V.; ...

2016-04-18

We present microscopic magnetic properties of a two-dimensional triangular lattice Sc 2Ga 2CuO 7, consisting of single and double triangular Cu planes. An antiferromagnetic (AFM) exchange interaction J/k B ≈ 35 K between Cu 2+ (S = 1/2) spins in the triangular biplane is obtained from the analysis of intrinsic magnetic susceptibility data. The intrinsic magnetic susceptibility, extracted from 71Ga NMR shift data, displays the presence of AFM short range spin correlations and remains finite down to 50 mK, suggesting a nonsinglet ground state. The nuclear spin-lattice relaxation rate (1/T 1) reveals a slowing down of Cu 2+ spin fluctuationsmore » with decreasing T down to 100 mK. Magnetic specific heat (C m) and 1/T 1 exhibit power law behavior at low temperatures, implying the gapless nature of the spin excitation spectrum. The absence of long range magnetic ordering down to ~J/700, nonzero spin susceptibility at low T, and the power law behavior of C m and 1/T 1 suggest a gapless quantum spin liquid (QSL) state. Our results demonstrate that persistent spin dynamics induced by frustration maintain a quantum-disordered state at T → 0 in this triangular lattice antiferromagnet. Furthermore, this suggests that the low energy modes are dominated by spinon excitations in the QSL state due to randomness engendered by disorder and frustration.« less

Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

PubMed Central

Marino, A.; Cammarata, M.; Matar, S. F.; Létard, J.-F.; Chastanet, G.; Chollet, M.; Glownia, J. M.; Lemke, H. T.; Collet, E.

2015-01-01

We combine ultrafast optical spectroscopy with femtosecond X-ray absorption to study the photo-switching dynamics of the [Fe(PM-AzA)2(NCS)2] spin-crossover molecular solid. The light-induced excited spin-state trapping process switches the molecules from low spin to high spin (HS) states on the sub-picosecond timescale. The change of the electronic state (<50 fs) induces a structural reorganization of the molecule within 160 fs. This transformation is accompanied by coherent molecular vibrations in the HS potential and especially a rapidly damped Fe-ligand breathing mode. The time-resolved studies evidence a delayed activation of coherent optical phonons of the lattice surrounding the photoexcited molecules. PMID:26798836

Elastic anomalies and acoustic dissipation associated with spin state transitions in LnCoO3 (Ln=La, Nd, Gd) and Co3O4: analogue behaviour for spin state transitions in minerals

NASA Astrophysics Data System (ADS)

Zhang, Z.; Carpenter, M. A.; Koppensteiner, J.; Schranz, W.

2010-12-01

Iron ions in lower mantle minerals magnesiowüstitue (Mg,Fe)O, perovskite (Mg,Fe)(Si,Al)O3 and post-perovskite phases undergo electronic spin state transitions from high spin (HS) to low spin (LS) or intermediate spin (IS) at high pressures and high temperatures. These spin state transitions give rise to changes in bulk and shear moduli which have significant implications for the physical and chemical properties of the lower mantle. However, the possibility of increased attenuation does not appear to have been considered yet. Co3+ is isoelectronic with Fe2+ and shows analogous HS/LS behaviour at ambient pressure in a temperature range which is easily accessible for in-situ investigations. We have studied spin state transitions in cobalt perovskites LaCoO3, NdCoO3, GdCoO3 and in Co3O4 using resonant ultrasound spectroscopy (RUS) at high frequencies 0.1-1.5 MHz, and dynamic mechanical analysis (DMA) at low frequencies 0.1-50 Hz, in the temperature range 10-1200 K. The specific objectives were to characterize anomalies in the shear moduli and in acoustic attenuation accompanying changes in the spin state of Co3+. Anomalies in shear moduli have been observed at ~110 K and ~590 K for LaCoO3, ~325 K and ~695 K for NdCoO3, ~720 K for GdCoO3, and ~30 K for Co3O4. For LaCoO3, a spin order parameter qspin is expected to couple with volume strain ea as λeaqspin and with shear strain es as λes2qspin. As a consequence of linear/quadratic coupling with es, the shear modulus is expected to vary linearly with qspin. This appears to be approximately the case for LaCoO3. Changes in spin state do not appear to give rise to acoustic attenuation at either DMA frequencies (~1 Hz) or RUS frequencies (~1 MHz), consistent with the expectation that spin/lattice relaxation is rapid in comparison with the time scale of applied stress in each case. On the other hand, for LaCoO3 there is a peak in dissipation near 590 K at low frequencies, which is attributed to freezing of ferroelastic twin

The Korean Diasporic Experience: Measuring Ethnic Identity in the United States and China.

ERIC Educational Resources Information Center

Lee, Richard M.; Falbo, Toni; Doh, Hyun Sim; Park, Seong Yeon

2001-01-01

Korean undergraduates living in the United States and in China were administered the Multigroup Ethnic Identity Measure to assess their ethnic identity. Korean Americans had higher scores on ethnic identity and were more likely to be classified as bicultural, indicating that they were able to retain their cultural heritage while incorporating…

Magnetization distribution and spin transport of graphene/h-BN/graphene nanoribbon-based magnetic tunnel junction

NASA Astrophysics Data System (ADS)

Zhang, Y.; Yan, X. H.; Guo, Y. D.; Xiao, Y.

2017-09-01

Motivated by recent electronic transport measurement of boron nitride-graphene hybrid atomic layers, we studied magnetization distribution, transmission and current-bias relation of graphene/h-BN/graphene (C/BN/C) nanoribbon-based magnetic tunnel junctions (MTJ) based on density functional theory and non-equilibrium Green's function methods. Three types of MTJs, i.e. asymmetric, symmetric (S) and symmetric (SS), and two types of lead magnetization alignment, i.e. parallel (PC) and antiparallel (APC), are considered. The results show that the magnetization distribution is closely related to the interface structure. Especially for asymmetric MTJ, the B/N atoms at the C/BN interface are spin-polarized and give finite magnetic moments. More interesting, it is found that the APC transmission of asymmetric MTJ with the thinnest barrier dominates over the PC one. By analyzing the projected density of states, one finds that the unusual higher APC transmission than PC is due to the coupling of electronic states of left ZGNR and right ZGNR. By integrating transmission, we calculate the current-bias voltage relation and find that the APC current is larger than PC current at small bias voltage and therefore reproduces a negative tunnel magnetoresistance. The results reported here will be useful and important for the design of C/BN/C-based MTJ.

Theory of Spin States of Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

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

2007-04-01

The photoluminescence spectrum of an asymmetric pair of coupled InAs quantum dots in an applied electric field shows a rich pattern of level anticrossings, crossings and fine structure that can be understood as a superposition of charge and spin configurations. We present a theoretical model that provides a description of the energy positions and intensities of the optical transitions in exciton, biexciton and charged exciton states of coupled quantum dots molecules.

Optical evidence for the spin-state disorder in LaCo1-x Rh x O3

NASA Astrophysics Data System (ADS)

Terasaki, Ichiro; Asai, Shinichiro; Taniguchi, Hiroki; Okazaki, Ryuji; Yasui, Yukio; Ikemoto, Yuka; Moriwaki, Taro

2017-06-01

We have measured the infrared reflectivity of single-crystalline samples of LaCo1-x Rh x O3 (x  =  0, 0.05 and 0.10) from 10 to 300 K from 0.05 to 0.15 eV. We find that the optical phonons of the Co-O stretching mode depend on temperature and the Rh content. Analysis with three Lorentz oscillators reveals that the spin state of Co3+ in LaCo1-x Rh x O3 can be understood in terms of a solid solution of low-spin- and high-spin-state Co3+ ions, and the substituted Rh ion retains some fraction of the high-spin Co3+ ions down to low temperature.

Effective field renormalization group approach for Ising lattice spin systems

NASA Astrophysics Data System (ADS)

Fittipaldi, Ivon P.

1994-03-01

A new applicable real-space renormalization group framework (EFRG) for computing the critical properties of Ising lattice spin systems is presented. The method, which follows up the same strategy of the mean-field renormalization group scheme (MFRG), is based on rigorous Ising spin identities and utilizes a convenient differential operator expansion technique. Within this scheme, in contrast with the usual mean-field type of equation of state, all the relevant self-spin correlations are taken exactly into account. The results for the critical coupling and the critical exponent v, for the correlation length, are very satisfactory and it is shown that this technique leads to rather accurate results which represent a remarkable improvement on those obtained from the standard MFRG method. In particular, it is shown that the present EFRG approach correctly distinguishes the geometry of the lattice structure even when employing its simplest size-cluster version. Owing to its simplicity we also comment on the wide applicability of the present method to problems in crystalline and disordered Ising spin systems.

Bulk electron spin polarization generated by the spin Hall current

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2006-07-01

It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

Studying Dynamics by Magic-Angle Spinning Solid-State NMR Spectroscopy: Principles and Applications to Biomolecules

PubMed Central

Schanda, Paul; Ernst, Matthias

2016-01-01

Magic-angle spinning solid-state NMR spectroscopy is an important technique to study molecular structure, dynamics and interactions, and is rapidly gaining importance in biomolecular sciences. Here we provide an overview of experimental approaches to study molecular dynamics by MAS solid-state NMR, with an emphasis on the underlying theoretical concepts and differences of MAS solid-state NMR compared to solution-state NMR. The theoretical foundations of nuclear spin relaxation are revisited, focusing on the particularities of spin relaxation in solid samples under magic-angle spinning. We discuss the range of validity of Redfield theory, as well as the inherent multi-exponential behavior of relaxation in solids. Experimental challenges for measuring relaxation parameters in MAS solid-state NMR and a few recently proposed relaxation approaches are discussed, which provide information about time scales and amplitudes of motions ranging from picoseconds to milliseconds. We also discuss the theoretical basis and experimental measurements of anisotropic interactions (chemical-shift anisotropies, dipolar and quadrupolar couplings), which give direct information about the amplitude of motions. The potential of combining relaxation data with such measurements of dynamically-averaged anisotropic interactions is discussed. Although the focus of this review is on the theoretical foundations of dynamics studies rather than their application, we close by discussing a small number of recent dynamics studies, where the dynamic properties of proteins in crystals are compared to those in solution. PMID:27110043

Spin-state transitions and magnetic polaron in lightly doped La1-xSrxCoO3.

NASA Astrophysics Data System (ADS)

Podlesnyak, A.; Haverkort, M. W.; Conder, K.; Pomyakushina, E.; Khomskii, Daniel

2007-03-01

Using the inelastic neutron scattering (INS) technique, we identified the energy levels of the thermally excited states of Co^3+ ions in both LaCoO3 and La0.998Sr0.002CoO3. In LaCoO3 an excitation at ˜0.6 meV appears at T>30K, whose intensity follows the bulk magnetization. Within a model including crystal field interaction and spin-orbit coupling we interpret this excitation as originating from a transition between thermally excited states located about 120 K above the ground state. Since the g-factor obtained from the field dependence of the INS is g˜ 3, we interpret this state as a high-spin state of Co^3+ . The lightly doped material x˜0:002 exhibits paramagnetic properties at low temperatures. An INS peak at energy transfer ˜0.75 meV was observed in it already at T = 1:5 K. We propose that the holes introduced in the LS state of LaCoO3 by doping are extended over the neighboring Co sites, forming thus magnetic polaron and transforming all the involved Co ions (e.g. 6 of them) to the high-spin state. Similarly to LaCoO3, we interpret the INS transition at 0.75 meV as that on these high-spin Co^3+ ions.

Suppression of electron spin decoherence in Rabi oscillations induced by an inhomogeneous microwave field

NASA Astrophysics Data System (ADS)

Saiko, A. P.; Fedaruk, R.; Markevich, S. A.

2018-05-01

The decay of Rabi oscillations provides direct information about coherence of electron spins. When observed in EPR experiments, it is often shortened by spatial inhomogeneity of the microwave field amplitude in a bulk sample. In order to suppress this undesired loss of coherence, we propose an additional dressing of spin states by a weak longitudinal continuous radiofrequency field. The Gaussian, cosine and linear distributions of the microwave amplitude is analyzed. Our calculations of the Rabi oscillations between the doubly dressed spin states show that for all these distributions the maximum suppression of the inhomogeneity-induced decoherence is achieved at the so-called Rabi resonance when the radio-field frequency is in resonance with the Rabi frequency of spins in the microwave field. The manifestations of such suppression in the published EPR experiments with the bichromatic driving are discussed. The realization of the Rabi resonance using the radiofrequency field could open new possibilities for separating the contributions of relaxation mechanisms from those due to the inhomogeneous driving in spin decoherence.

Spin-correlated doublet pairs as intermediate states in charge separation processes

NASA Astrophysics Data System (ADS)

Kraffert, Felix; Behrends, Jan

2017-10-01

Spin-correlated charge-carrier pairs play a crucial role as intermediate states in charge separation both in natural photosynthesis as well as in solar cells. Using transient electron paramagnetic resonance (trEPR) spectroscopy in combination with spectral simulations, we study spin-correlated polaron pairs in polymer:fullerene blends as organic solar cells materials. The semi-analytical simulations presented here are based on the well-established theoretical description of spin-correlated radical pairs in biological systems, however, explicitly considering the disordered nature of polymer:fullerene blends. The large degree of disorder leads to the fact that many different relative orientations between both polarons forming the spin-correlated pairs have to be taken into account. This has important implications for the spectra, which differ significantly from those of spin-correlated radical pairs with a fixed relative orientation. We systematically study the influence of exchange and dipolar couplings on the trEPR spectra and compare the simulation results to measured X- and Q-band trEPR spectra. Our results demonstrate that assuming dipolar couplings alone does not allow us to reproduce the experimental spectra. Due to the rather delocalised nature of polarons in conjugated organic semiconductors, a significant isotropic exchange coupling needs to be included to achieve good agreement between experiments and simulations.

Quantum spin circulator in Y junctions of Heisenberg chains

NASA Astrophysics Data System (ADS)

Buccheri, Francesco; Egger, Reinhold; Pereira, Rodrigo G.; Ramos, Flávia B.

2018-06-01

We show that a quantum spin circulator, a nonreciprocal device that routes spin currents without any charge transport, can be achieved in Y junctions of identical spin-1 /2 Heisenberg chains coupled by a chiral three-spin interaction. Using bosonization, boundary conformal field theory, and density matrix renormalization group simulations, we find that a chiral fixed point with maximally asymmetric spin conductance arises at a critical point separating a regime of disconnected chains from a spin-only version of the three-channel Kondo effect. We argue that networks of spin-chain Y junctions provide a controllable approach to construct long-sought chiral spin-liquid phases.

Simultaneous optimization of spin fluctuations and superconductivity under pressure in an iron-based superconductor.

PubMed

Ji, G F; Zhang, J S; Ma, Long; Fan, P; Wang, P S; Dai, J; Tan, G T; Song, Y; Zhang, C L; Dai, Pengcheng; Normand, B; Yu, Weiqiang

2013-09-06

We present a high-pressure NMR study of the overdoped iron pnictide superconductor NaFe0.94Co0.06As. The low-energy antiferromagnetic spin fluctuations in the normal state, manifest as the Curie-Weiss upturn in the spin-lattice relaxation rate 1/(75)T1T, first increase strongly with pressure but fall again at P>Popt=2.2  GPa. Neither long-ranged magnetic order nor a structural phase transition is encountered up to 2.5 GPa. The superconducting transition temperature Tc shows a pressure dependence identical to the spin fluctuations. Our observations demonstrate that magnetic correlations and superconductivity are optimized simultaneously as a function of the electronic structure, thereby supporting very strongly a magnetic origin of superconductivity.

On the spin states of habitable zone exoplanets around M dwarfs: the effect of a near-resonant companion

NASA Astrophysics Data System (ADS)

Vinson, Alec M.; Hansen, Brad M. S.

2017-12-01

One long-standing problem for the potential habitability of planets within M dwarf systems is their likelihood to be tidally locked in a synchronously rotating spin state. This problem thus far has largely been addressed only by considering two objects: the star and the planet itself. However, many systems have been found to harbour multiple planets, with some in or very near to mean motion resonances. The presence of a planetary companion near a mean motion resonance can induce oscillatory variations in the mean motion of the planet, which we demonstrate can have significant effects on the spin state of an otherwise synchronously rotating planet. In particular, we find that a planetary companion near a mean motion resonance can excite the spin states of planets in the habitable zone of small, cool stars, pushing otherwise synchronously rotating planets into higher amplitude librations of the spin state, or even complete circulation resulting in effective stellar days with full surface coverage on the order of years or decades. This increase in illuminated area can have potentially dramatic influences on climate, and thus on habitability. We also find that the resultant spin state can be very sensitive to initial conditions due to the chaotic nature of the spin state at early times within certain regimes. We apply our model to two hypothetical planetary systems inspired by the K00255 and TRAPPIST-1 systems, both of which have Earth-sized planets in mean motion resonances orbiting cool stars.

Preparing Greenberger-Horne-Zeilinger and W states on a long-range Ising spin model by global controls

NASA Astrophysics Data System (ADS)

Chen, Jiahui; Zhou, Hui; Duan, Changkui; Peng, Xinhua

2017-03-01

Entanglement, a unique quantum resource with no classical counterpart, remains at the heart of quantum information. The Greenberger-Horne-Zeilinger (GHZ) and W states are two inequivalent classes of multipartite entangled states which cannot be transformed into each other by means of local operations and classic communication. In this paper, we present the methods to prepare the GHZ and W states via global controls on a long-range Ising spin model. For the GHZ state, general solutions are analytically obtained for an arbitrary-size spin system, while for the W state, we find a standard way to prepare the W state that is analytically illustrated in three- and four-spin systems and numerically demonstrated for larger-size systems. The number of parameters required in the numerical search increases only linearly with the size of the system.

Gravity and the Spin-2 Planar Schrödinger Equation

NASA Astrophysics Data System (ADS)

Bergshoeff, Eric A.; Rosseel, Jan; Townsend, Paul K.

2018-04-01

A Schrödinger equation proposed for the Girvin-MacDonald-Platzman gapped spin-2 mode of fractional quantum Hall states is found from a novel nonrelativistic limit, applicable only in 2 +1 dimensions, of the massive spin-2 Fierz-Pauli field equations. It is also found from a novel null reduction of the linearized Einstein field equations in 3 +1 dimensions, and in this context a uniform distribution of spin-2 particles implies, via a Brinkmann-wave solution of the nonlinear Einstein equations, a confining harmonic oscillator potential for the individual particles.

Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

PubMed

Thygesen, Peter M M; Paddison, Joseph A M; Zhang, Ronghuan; Beyer, Kevin A; Chapman, Karena W; Playford, Helen Y; Tucker, Matthew G; Keen, David A; Hayward, Michael A; Goodwin, Andrew L

2017-02-10

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

Covariant Conservation Laws and the Spin Hall Effect in Dirac-Rashba Systems

NASA Astrophysics Data System (ADS)

Milletarı, Mirco; Offidani, Manuel; Ferreira, Aires; Raimondi, Roberto

2017-12-01

We present a theoretical analysis of two-dimensional Dirac-Rashba systems in the presence of disorder and external perturbations. We unveil a set of exact symmetry relations (Ward identities) that impose strong constraints on the spin dynamics of Dirac fermions subject to proximity-induced interactions. This allows us to demonstrate that an arbitrary dilute concentration of scalar impurities results in the total suppression of nonequilibrium spin Hall currents when only Rashba spin-orbit coupling is present. Remarkably, a finite spin Hall conductivity is restored when the minimal Dirac-Rashba model is supplemented with a spin-valley interaction. The Ward identities provide a systematic way to predict the emergence of the spin Hall effect in a wider class of Dirac-Rashba systems of experimental relevance and represent an important benchmark for testing the validity of numerical methodologies.

Enhanced spin pumping into superconductors provides evidence for superconducting pure spin currents

NASA Astrophysics Data System (ADS)

Jeon, Kun-Rok; Ciccarelli, Chiara; Ferguson, Andrew J.; Kurebayashi, Hidekazu; Cohen, Lesley F.; Montiel, Xavier; Eschrig, Matthias; Robinson, Jason W. A.; Blamire, Mark G.

2018-06-01

Unlike conventional spin-singlet Cooper pairs, spin-triplet pairs can carry spin1,2. Triplet supercurrents were discovered in Josephson junctions with metallic ferromagnet spacers, where spin transport can occur only within the ferromagnet and in conjunction with a charge current. Ferromagnetic resonance injects a pure spin current from a precessing ferromagnet into adjacent non-magnetic materials3,4. For spin-singlet pairing, the ferromagnetic resonance spin pumping efficiency decreases below the critical temperature (Tc) of a coupled superconductor5,6. Here we present ferromagnetic resonance experiments in which spin sink layers with strong spin-orbit coupling are added to the superconductor. Our results show that the induced spin currents, rather than being suppressed, are substantially larger in the superconducting state compared with the normal state; although further work is required to establish the details of the spin transport process, we show that this cannot be mediated by quasiparticles and is most likely a triplet pure spin supercurrent.

Bending strain engineering in quantum spin hall system for controlling spin currents

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

Huang, Bing; Jin, Kyung-Hwan; Cui, Bin

Quantum spin Hall system can exhibit exotic spin transport phenomena, mediated by its topological edge states. The concept of bending strain engineering to tune the spin transport properties of a quantum spin Hall system is demonstrated. Here, we show that bending strain can be used to control the spin orientation of counter-propagating edge states of a quantum spin system to generate a non-zero spin current. This physics mechanism can be applied to effectively tune the spin current and pure spin current decoupled from charge current in a quantum spin Hall system by control of its bending curvature. Moreover, the curvedmore » quantum spin Hall system can be achieved by the concept of topological nanomechanical architecture in a controllable way, as demonstrated by the material example of Bi/Cl/Si(111) nanofilm. This concept of bending strain engineering of spins via topological nanomechanical architecture affords a promising route towards the realization of topological nano-mechanospintronics.« less

Bending strain engineering in quantum spin hall system for controlling spin currents

DOE PAGES

Huang, Bing; Jin, Kyung-Hwan; Cui, Bin; ...

2017-06-16

Quantum spin Hall system can exhibit exotic spin transport phenomena, mediated by its topological edge states. The concept of bending strain engineering to tune the spin transport properties of a quantum spin Hall system is demonstrated. Here, we show that bending strain can be used to control the spin orientation of counter-propagating edge states of a quantum spin system to generate a non-zero spin current. This physics mechanism can be applied to effectively tune the spin current and pure spin current decoupled from charge current in a quantum spin Hall system by control of its bending curvature. Moreover, the curvedmore » quantum spin Hall system can be achieved by the concept of topological nanomechanical architecture in a controllable way, as demonstrated by the material example of Bi/Cl/Si(111) nanofilm. This concept of bending strain engineering of spins via topological nanomechanical architecture affords a promising route towards the realization of topological nano-mechanospintronics.« less