Thermal transport in disordered one-dimensional spin chains
NASA Astrophysics Data System (ADS)
Poboiko, Igor; Feigel'man, Mikhail
2015-12-01
We study a one-dimensional anisotropic XXZ Heisenberg spin-1/2 chain with weak random fields hizSiz by means of Jordan-Wigner transformation to spinless Luttinger liquid with disorder and bosonization technique. First, we reinvestigate the phase diagram of the system in terms of dimensionless disorder γ =
Langevin dynamics simulation of a one-dimensional linear spin chain with long-range interactions
NASA Astrophysics Data System (ADS)
Ati, Moncef; Enachescu, Cristian; Bouamrane, Rachid
2017-07-01
In this paper we study the critical behavior of a simple one-dimensional rotor spin in the form of a linear chain with long-range interactions, using the mean field Langevin dynamics approach and in the presence of fluctuations added by a heat bath. We have computed the specific heat, the magnetic susceptibility, the Binder fourth-order cumulant, and the magnetization, and then we have calculated the critical exponents using finite-size scaling. In addition, we provide a relation between the thermal bath temperature and the temperature of the system. Our results confirm the existence of a second-order critical temperature in the one-dimensional chain of spins with long-range interaction.
Hidden Rashba spin-split states in a quasi-one-dimensional Au atomic chain on ferromagnetic Ni(110)
NASA Astrophysics Data System (ADS)
Warashina, Takuya; Nurmamat, Munisa; Miyamoto, Koji; Shishidou, Tatsuya; Taniguchi, Masaki; Kimura, Akio; Okuda, Taichi
2016-12-01
An electronic structure of a Au atomic chain on Ni(110), which was investigated decades ago, has been reinvestigated by high-resolution spin- and angle-resolved photoemission spectroscopy. Clear evidence of a Rashba spin split, i.e., spin-polarization reversal between positive and negative wave vectors with respect to the symmetry point, has been observed in the electronic bands possessing quasi-one-dimensional character. The observed spin-split state caused by spin-orbit interaction (SOI) was overlooked in the previous spin-resolved photoemission study probably due to the dominant effect of exchange splitting of the Ni substrate than the Rashba effect and poorer resolution of the previous measurement. The system containing both the Rashba-type SOI and the exchange interaction with one-dimensional character will provide a platform to investigate the effect of exchange interaction on the spin-split states caused by SOI with low dimensionality.
One-dimensional spinon spin currents
NASA Astrophysics Data System (ADS)
Hirobe, Daichi; Sato, Masahiro; Kawamata, Takayuki; Shiomi, Yuki; Uchida, Ken-Ichi; Iguchi, Ryo; Koike, Yoji; Maekawa, Sadamichi; Saitoh, Eiji
2017-01-01
Quantum spin fluctuation in a low-dimensional or frustrated magnet breaks magnetic ordering while keeping spin correlation. Such fluctuation has been a central topic in magnetism because of its relevance to high-Tc superconductivity and topological states. However, utilizing such spin states has been quite difficult. In a one-dimensional spin-1/2 chain, a particle-like excitation called a spinon is known to be responsible for spin fluctuation in a paramagnetic state. Spinons behave as a Tomonaga-Luttinger liquid at low energy, and the spin system is often called a quantum spin chain. Here we show that a quantum spin chain generates and carries spin current, which is attributed to spinon spin current. This is demonstrated by observing an anisotropic negative spin Seebeck effect along the spin chains in Sr2CuO3. The results show that spin current can flow even in an atomic channel owing to long-range spin fluctuation.
Thermodynamics of spin chains of Haldane-Shastry type and one-dimensional vertex models
Enciso, Alberto; Finkel, Federico; Gonzalez-Lopez, Artemio
2012-11-15
We study the thermodynamic properties of spin chains of Haldane-Shastry type associated with the A{sub N-1} root system in the presence of a uniform external magnetic field. To this end, we exactly compute the partition function of these models for an arbitrary finite number of spins. We then show that these chains are equivalent to a suitable inhomogeneous classical Ising model in a spatially dependent magnetic field, generalizing the results of Basu-Mallick et al. for the zero magnetic field case. Using the standard transfer matrix approach, we are able to compute in closed form the free energy per site in the thermodynamic limit. We perform a detailed analysis of the chains' thermodynamics in a unified way, with special emphasis on the zero field and zero temperature limits. Finally, we provide a novel interpretation of the thermodynamic quantities of spin chains of Haldane-Shastry type as weighted averages of the analogous quantities over an ensemble of classical Ising models. - Highlights: Black-Right-Pointing-Pointer Partition function of spin chains of Haldane-Shastry type in magnetic field. Black-Right-Pointing-Pointer Equivalence to classical inhomogeneous Ising models. Black-Right-Pointing-Pointer Free energy per site, other thermodynamic quantities in thermodynamic limit. Black-Right-Pointing-Pointer Zero field, zero temperature limits. Black-Right-Pointing-Pointer Thermodynamic equivalence with ensemble of classical Ising models.
Generation of concurrence between two qubits locally coupled to a one-dimensional spin chain
NASA Astrophysics Data System (ADS)
Nag, Tanay; Dutta, Amit
2016-08-01
We consider a generalized central spin model, consisting of two central qubits and an environmental spin chain (with periodic boundary condition) to which these central qubits are locally and weakly connected either at the same site or at two different sites separated by a distance d . Our purpose is to study the subsequent temporal generation of entanglement, quantified by concurrence, when initially the qubits are in an unentangled state. In the equilibrium situation, we show that the concurrence survives for a larger value of d when the environmental spin chain is critical. Importantly, a common feature observed both in the equilibrium and the nonequilibrium situations while the latter is created by a sudden but global change of the environmental transverse field is that the two qubits become maximally entangled for the critical quenching. Following a nonequilibrium evolution of the spin chain, our study for d ≠0 indicates that there exists a threshold time above which concurrence attains a finite value. Additionally, we show that the number of independent decohering channels (DCs) is determined by d as well as the local difference of the transverse field of the two underlying Hamiltonians governing the time evolution; the concurrence can be enhanced by a higher number of independent channels. The qualitatively similar behavior displayed by the concurrence for critical and off-critical quenches, as reported here, is characterized by analyzing the nonequilibrium evolution of these channels. The concurrence is maximum when the decoherence factor or the echo associated with the most rapidly DC decays to zero; on the contrary, the condition when the concurrence vanishes is determined nontrivially by the associated decay of one of the intermediate DCs. Analyzing the reduced density of a single qubit, we also explain the observation that the dephasing rate is always slower than the unentanglement rate. We further establish that the maximally and minimally decohering
NASA Astrophysics Data System (ADS)
Popov, Alexander P.; Gloria Pini, Maria; Rettori, Angelo
2016-03-01
The metastable states of a finite-size chain of N classical spins described by the chiral XY-model on a discrete one-dimensional lattice are calculated by means of a general theoretical method recently developed by one of us. This method allows one to determine all the possible equilibrium magnetic states in an accurate and systematic way. The ground state of a chain consisting of N classical XY spins is calculated in the presence of (i) a symmetric ferromagnetic exchange interaction, favoring parallel alignment of nearest neighbor spins, (ii) a uniaxial anisotropy, favoring a given direction in the film plane, and (iii) an antisymmetric Dzyaloshinskii-Moriya interaction (DMI), favoring perpendicular alignment of nearest neighbor spins. In addition to the ground state with a non-uniform helical spin arrangement, which originates from the energy competition in the finite-size chain with open boundary conditions, we have found a considerable number of higher-energy equilibrium states. In the investigated case of a chain with N=10 spins and a DMI much smaller than the in-plane uniaxial anisotropy, it turns out that a metastable (unstable) state of the finite chain is characterized by a configuration where none (at least one) of the inner spins is nearly parallel to the hard axis. The role of the DMI is to establish a unique rotational sense for the helical ground state. Moreover, the number of both metastable and unstable equilibrium states is doubled with respect to the case of zero DMI. This produces modifications in the Peierls-Nabarro potential encountered by a domain wall during its displacement along the discrete spin chain.
NASA Astrophysics Data System (ADS)
Ghosh, Joydip
2014-12-01
Spin-1 systems, in comparison to spin-1/2 systems, offer a better security for encoding and transferring quantum information, primarily due to their larger Hilbert spaces. Superconducting artificial atoms possess multiple energy levels, thereby being capable of emulating higher-spin systems. Here I consider a one-dimensional lattice of nearest-neighbor-coupled superconducting transmon systems, and devise a scheme to transfer an arbitrary qutrit state (a state encoded in a three-level quantum system) across the chain. I assume adjustable couplings between adjacent transmons, derive an analytic constraint for the control pulse, and show how to satisfy the constraint to achieve a high-fidelity state transfer under current experimental conditions. My protocol thus enables enhanced quantum communication and information processing with promising superconducting qutrits.
NASA Astrophysics Data System (ADS)
Nag, Tanay
2016-06-01
We take a central spin model (CSM), consisting of a one-dimensional environmental Ising spin chain and a single qubit connected globally to all the spins of the environment, to study the excess energy (EE) of the environment and the logarithm of decoherence factor namely, generalized fidelity susceptibility per site (GFSS), associated with the qubit under a periodic driving of the transverse field term of environment across its critical point using the Floquet theory. The coupling to the qubit, prepared in a pure state, with the transverse field of the spin chain yields two sets of EE corresponding to the two species of Floquet operators. In the limit of weak coupling, we derive an approximated expression of GFSS after an infinite number of driving period which can successfully estimate the low- and intermediate-frequency behavior of GFSS obtained numerically with a large number of time periods. Our main focus is to analytically investigate the effect of system-environment coupling strength on the EEs and GFSS and relate the behavior of GFSS to EEs as a function of frequency by plausible analytical arguments. We explicitly show that the low-frequency beatinglike pattern of GFSS is an outcome of two frequencies, causing the oscillations in the two branches of EEs, that are dependent on the coupling strength. In the intermediate frequency regime, dip structure observed in GFSS can be justified by the resonance peaks of EEs at those coupling parameter-dependent frequencies; high-frequency saturation behavior of EEs and GFSS are controlled by the same static Hamiltonian and the associated saturation values are related to the coupling strength.
NASA Astrophysics Data System (ADS)
Jiang, Jian-Jun; Liu, Yong-Jun; Zhang, Song-Jun; Yang, Cui-Hong
2009-10-01
We investigate the effect of frustration on spin-wave excitation spectra and the properties of the quasi-one-dimensional Heisenberg chain using a spin-wave-wave analysis, the exact diagonalization method and the density matrix renormalization group method. The results show that frustration can cause the softening of the acoustic excitation spectrum ω3, as well as the hardening of the optical excitation spectrum ω1. As a function of the frustration parameter α, the phase diagram exhibits a ferromagnetic phase, a narrow canted phase and a singlet phase. The results obtained from numerical methods show that the spin gap obviously opens and the tetramer-dimer state dominates the properties of the ground state in the singlet phase.
Bridging frustrated-spin-chain and spin-ladder physics: Quasi-one-dimensional magnetism of BiCu2PO6
NASA Astrophysics Data System (ADS)
Tsirlin, Alexander A.; Rousochatzakis, Ioannis; Kasinathan, Deepa; Janson, Oleg; Nath, Ramesh; Weickert, Franziska; Geibel, Christoph; Läuchli, Andreas M.; Rosner, Helge
2010-10-01
We derive and investigate the microscopic model of the quantum magnet BiCu2PO6 using band-structure calculations, magnetic susceptibility and high-field magnetization measurements, as well as exact diagonalization (ED) and density-matrix renormalization group (DMRG) techniques. The resulting quasi-one-dimensional spin model is a two-leg antiferromagnetic ladder with frustrating next-nearest-neighbor couplings along the legs. The individual couplings are estimated from band-structure calculations and by fitting the magnetic susceptibility with theoretical predictions, obtained using full diagonalizations. The nearest-neighbor leg coupling J1 , the rung coupling J4 , and one of the next-nearest-neighbor couplings J2 amount to 120-150 K while the second next-nearest-neighbor coupling is J2'≃J2/2 . The spin ladders do not match the structural chains, and although the next-nearest-neighbor interactions J2 and J2' have very similar superexchange pathways, they differ substantially in magnitude due to a tiny difference in the O-O distances and in the arrangement of nonmagnetic PO4 tetrahedra. An extensive ED study of the proposed model provides the low-energy excitation spectrum and shows that the system is in the strong rung coupling regime. The strong frustration by the next-nearest-neighbor couplings leads to a triplon branch with an incommensurate minimum. This is further corroborated by a strong-coupling expansion up to second order in the inter-rung coupling. Based on high-field magnetization measurements, we estimate the spin gap of Δ≃32K and suggest the likely presence of antisymmetric Dzyaloshinskii-Moriya anisotropy and interladder coupling J3 . We also provide a tentative description of the physics of BiCu2PO6 in magnetic field, in the light of the low-energy excitation spectra and numerical calculations based on ED and DMRG. In particular, we raise the possibility for a rich interplay between one- and two-component Luttinger liquid phases and a
One-dimensional quantum spin heterojunction as a thermal switch
NASA Astrophysics Data System (ADS)
Yang, Chuan-Jing; Jin, Li-Hui; Gong, Wei-Jiang
2016-03-01
We study the thermal transport through a quantum spin-1 2 heterojunction, which consists of a finite-size chain with two-site anisotropic XY interaction and three-site XZX+YZY interaction coupled at its ends to two semi-infinite isotropic XY chains. By performing the Jordan-Wigner transformation, the original spin Hamiltonian is mapped onto a fermionic Hamiltonian. Then, the fermionic structure is discussed, and the heat current as a function of structural parameters is evaluated. It is found that the magnetic fields applied at respective chains play different roles in adjusting the heat current in this heterojunction. Moreover, the interplay between the anisotropy of the XY interaction and the three-site spin interaction assists to further control the thermal transport. In view of the numerical results, we propose this heterojunction to be an alternate candidate for manipulating the heat current in one-dimensional (1D) systems.
Zeng, Jing; Chen, Ke-Qiu
2017-04-05
In experimental studies, magnetoresistance (MR) values of 10(3) are hard to reach for conventional single-molecule spin-valves. Motivated by a recent experiment [Nano Lett., 2016, 16, 577-582], where tailored Co-salophene-based all-spin molecular devices are successfully realized, we demonstrate the functionality of a Co-salophene-based spin chain without magnetic electrodes. By using nonequilibrium Green's functions in combination with density functional theory, we find that the maximum MR ratio of this spin chain can reach 10(6) by manipulating its spins in a controlled way, which is several orders of magnitude higher than previously reported experimental values. As the Co-salophene-based spin chain has been successfully synthesized, we are highly expectant of the experimental realization of huge MR ratios.
The Recursion Method Applied to One-Dimensional Spin Systems
NASA Astrophysics Data System (ADS)
Viswanath, V. S.
The recursion method is used for the study of the dynamics of quantum spin models at zero and infinite temperatures. Two alternative formulations of the recursion method are described in detail. Application of either formulation to quantum many-body systems yields a set of continued-fraction coefficients. Several new calculational techniques for the analysis of these continued-fraction coefficients developed during the course of my research are presented. The efficacy and accuracy of these techniques are demonstrated by applications to the few situations were exact nontrivial results are available. For the s = 1/2 XXZ model on a linear chain, new and reliable quantitative information has been obtained on the type of ordering in the ground-state, on the size of gaps in the dynamically relevant excitation spectrum, on the bandwidths of dominant structures in spectral densities, on the exponents of infrared singularities in the same functions, and on the detailed shape of spectral-weight distributions. Zero temperature dynamic structure factors for the one-dimensional spin-s XYZ model in a magnetic field have been calculated for systems with s = 1/2, 1, 3/2. The line shapes and peak positions have been shown to differ considerably from the corresponding spin-wave results. Time-dependent spin autocorrelation functions and their spectral densities for the semi-infinite one -dimensional s = 1/2 XY model at infinite temperature have been determined in part by rigorous calculations in the fermion representation and in part by the recursion method in the spin representation. The study of boundary effects yields valuable new insight into the dynamical processes which govern the transport of spin fluctuations in that model. The exact results also provide a benchmark against which the results of the recursion method have been compared and calibrated.
One-dimensional Pt induced chains on Si(337)
NASA Astrophysics Data System (ADS)
McChesney, Jessica; Bostwick, A.; Rotenberg, E.; Lapeyre, Gerald
2006-03-01
The use of high index Si surfaces as templates for the formation of adsorbate induced one-dimensional chain structures have attracted considerable interest. These systems have been used as a test bed in which to study low-dimension physics and components of nanoelectronics. In addition to the Ag and Au induced chains reported to form on the Si(337) surface, Pt also produces one-dimensional chains. Angle-resolved photoemission spectroscopy was used to investigate the electronic structure of these new Pt chains. The valence band mapping confirms the one-dimensional nature of these chains as seen in LEED. Supported by ONR and DOE.
Tangoulis, V; Lalia-Kantouri, M; Gdaniec, M; Papadopoulos, Ch; Miletic, V; Czapik, A
2013-06-03
Two new six-coordinated high-spin Co(II) complexes have been synthesized through the reactions of Co(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO2-saloH) or 3-methoxy-salicylaldehyde (3-OCH3-saloH) under argon atmosphere: [Co(dpamH)2(5-NO2-salo)]NO3 (1) and [Co(dpamH)2(3-OCH3-salo)]NO3·1.3 EtOH·0.4H2O (2). According to the crystal packing of compound 1, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N-H···O and C-H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π-π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound 2 reveals a 1D assembly consisting solely from the coordination cations, which is formed by π-π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N-H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2-300 K on the basis of an empirical expression which allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin S(eff) = 1/2. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound 2. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δr/k(B) = 55(1) K for the [10-1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character.
A new magnetic phase diagram for the quasi-one-dimensional (1D) spin chain compound Ca3Co2O6
NASA Astrophysics Data System (ADS)
Srikanth, Hari; Lampen, P.; Bingham, N. S.; Phan, M. H.; Yi, H. T.; Cheong, S. W.
2015-03-01
The spin chain cobaltite system Ca3Co2O6 combines geometric frustration with intrinsic low-dimensionality, giving rise to complex physical phenomena that continue to attract a great deal of interest. A long-wavelength spin-density wave (SDW) has recently been observed in Ca3Co2O6 at zero field, stabilized by a helical exchange pathway among neighboring chains. We establish a new and more comprehensive phase diagram for this exotic system through the evolution of the magnetic entropy change ΔSM (T,H) associated with the magnetocaloric effect. ΔSM measurements in a single crystal of Ca3Co2O6 prepared by the flux method demonstrate the suppression of the SDW modulation by small applied magnetic fields (<1T). Metamagnetic transitions to a ferrimagnetic up-up-down spin chain arrangement and full ferromagnetic alignment are observed below 25 K. Short-range ordered (SRO) correlations with an antiferromagnetic character grow in volume as the temperature is lowered below 15 K, resulting in a crossover from ΔSM (H) <0 to ΔSM (H) >0 at 12 K. Our entropy-based analysis reflects current understanding of the role of SDW and SRO phases in Ca3Co2O6, resolves new sub-features of the ferrimagnetic phase, and extends previous results below the onset of slow dynamics (~ 10 K). USF authors acknowledge DoE BES under Award # DE-FG02-07ER46438 (magnetic measurements and analysis).
One-Dimensional Ising Model with "k"-Spin Interactions
ERIC Educational Resources Information Center
Fan, Yale
2011-01-01
We examine a generalization of the one-dimensional Ising model involving interactions among neighbourhoods of "k" adjacent spins. The model is solved by exploiting a connection to an interesting computational problem that we call ""k"-SAT on a ring", and is shown to be equivalent to the nearest-neighbour Ising model in the absence of an external…
One-Dimensional Ising Model with "k"-Spin Interactions
ERIC Educational Resources Information Center
Fan, Yale
2011-01-01
We examine a generalization of the one-dimensional Ising model involving interactions among neighbourhoods of "k" adjacent spins. The model is solved by exploiting a connection to an interesting computational problem that we call ""k"-SAT on a ring", and is shown to be equivalent to the nearest-neighbour Ising model in the absence of an external…
Spin accumulation on a one-dimensional mesoscopic Rashba ring.
Zhang, Zhi-Yong
2006-04-26
The nonequilibrium spin accumulation on a one-dimensional (1D) mesoscopic Rashba ring is investigated with unpolarized current injected through ideal leads. Due to the Rashba spin-orbit (SO) coupling and back-scattering at the interfaces between the leads and the ring, a beating pattern is formed in the fast oscillation of spin accumulation. If every beating period is complete, a plateau is formed, where the variation of spin accumulation with the external voltage is slow, but if new incomplete periods emerge in the envelope function, a transitional region appears. This plateau structure and the beating pattern are related to the tunnelling through spin-dependent resonant states. Because of the Aharonov-Casher (AC) effect, the average spin accumulation oscillates quasi-periodically with the Rashba SO coupling and has a series of zeros. In some situations, the direction of the average spin accumulation can be reversed by the external voltage in this 1D Rashba ring.
Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV{sub 2}O{sub 6}
Nandi, M.; Mandal, P.
2016-04-07
We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV{sub 2}O{sub 6} by magnetization and heat capacity measurements. Both monoclinic α-CoV{sub 2}O{sub 6} and triclinic γ-CoV{sub 2}O{sub 6} exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV{sub 2}O{sub 6}, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6 K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H–T phase diagram. As compared to α-CoV{sub 2}O{sub 6}, γ-CoV{sub 2}O{sub 6} displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV{sub 2}O{sub 6} may be considered as a magnetic refrigerant in the low-temperature region below 20 K.
NASA Astrophysics Data System (ADS)
Jiang, Hong; Hu, Xue-Ning; Zhao, Yin-chang; Zhang, Chao
2017-02-01
Spin excitation in poly(1,4-bis(2,2,6,6-tetramethyl-4-oxy-piperidyl-1-oxyl)-butadiin) (poly-BIPO), a quasi-one-dimensional organic ferromagnet, was investigated based on the extended Su-Schriffer-Heeger model by considering electron hopping and the spin correlation between the main chain and side radicals. The lattice, charge density, and spin density configurations of the single spin as well as spin domain excited states of the organic ferromagnet poly-BIPO were systematically studied. The side radical spin excitation gives rise to lattice distortion, charge density localization, and a spin density defect on the main chain. A peak induced by spin excitation is predicted to appear in the density of states of the organic ferromagnet poly-BIPO based on calculations for different spin electron states. These results expand knowledge on elementary excitation in organic materials and have significant implications for the design of spintronic devices.
Wave propagation in one-dimensional microscopic granular chains
NASA Astrophysics Data System (ADS)
Lin, Wei-Hsun; Daraio, Chiara
2016-11-01
We employ noncontact optical techniques to generate and measure stress waves in uncompressed, one-dimensional microscopic granular chains, and support our experiments with discrete numerical simulations. We show that the wave propagation through dry particles (150 μm radius) is highly nonlinear and it is significantly influenced by the presence of defects (e.g., surface roughness, interparticle gaps, and misalignment). We derive an analytical relation between the group velocity and gap size, and define bounds for the formation of highly nonlinear solitary waves as a function of gap size and axial misalignment.
NASA Astrophysics Data System (ADS)
Niesen, S. K.; Breunig, O.; Salm, S.; Seher, M.; Valldor, M.; Warzanowski, P.; Lorenz, T.
2014-09-01
BaCo2V2O8 is a quasi-one-dimensional antiferromagnetic spin-1/2 chain system with pronounced Ising anisotropy of the magnetic exchange. Due to finite interchain interactions, long-range antiferromagnetic order develops below TN≃5.5K, which is accompanied by a structural distortion in order to lift magnetic frustration effects. The corresponding temperature versus magnetic-field phase diagram is highly anisotropic with respect to the magnetic-field direction and various details are still under vivid discussion. Here, we report the influence of several substitutions on the magnetic properties and the phase diagrams of BaCo2V2O8. We investigate the substitution series Ba1-xSrxCo2V2O8 over the full range 0≤x≤1 as well as the influence of a partial substitution of the magnetic Co2+ by small amounts of other magnetic transition metals or by nonmagnetic magnesium. In all cases, the phase diagrams were obtained on single crystals from magnetization data and/or high-resolution studies of the thermal expansion and magnetostriction.
Heat conduction in one-dimensional aperiodic quantum Ising chains.
Li, Wenjuan; Tong, Peiqing
2011-03-01
The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{α}. By increasing the ratio of couplings, the exponent α can be modulated from α > -1 to α < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed.
NASA Astrophysics Data System (ADS)
Merino, J.; Jacko, A. C.; Khosla, A. L.; Powell, B. J.
2016-11-01
We show how quasi-one-dimensional correlated insulating states arise at two-thirds filling in organometallic multinuclear coordination complexes described by layered decorated honeycomb lattices. The interplay of spin-orbit coupling and electronic correlations leads to pseudospin-one moments arranged in weakly coupled chains with highly anisotropic exchange and a large trigonal splitting. We show that the in-plane exchange coupling is very different from the interlayer coupling; in particular the latter is much larger, despite the underlying hopping integrals being close to isotropic. Surprisingly, the effective dimensionality of the pseudospin model is strongly dependent on the strength of the electronic correlations: With increasing Hubbard U the pseudospin-one model becomes increasingly one dimensional, even though the crystal is almost isotropic. We predict that the trigonal splitting leads to a quantum phase transition from a Haldane phase to a topologically trivial phase as the relative strength of the spin-orbit coupling increases.
Spin-drag relaxation time in one-dimensional spin-polarized Fermi gases
NASA Astrophysics Data System (ADS)
Rainis, Diego; Polini, Marco; Tosi, M. P.; Vignale, G.
2008-01-01
Spin propagation in systems of one-dimensional interacting fermions at finite temperature is intrinsically diffusive. The spreading rate of a spin packet is controlled by a transport coefficient termed “spin drag” relaxation time τsd . In this paper we present both numerical and analytical calculations of τsd for a two-component spin-polarized cold Fermi gas trapped inside a tight atomic waveguide. At low temperatures we find an activation law for τsd , in agreement with earlier calculations of Coulomb drag between slightly asymmetric quantum wires, but with a different and much stronger temperature dependence of the prefactor. Our results provide a fundamental input for microscopic time-dependent spin-density functional theory calculations of spin transport in one-dimensional inhomogeneous systems of interacting fermions.
Emulating the one-dimensional Fermi-Hubbard model by a double chain of qubits
NASA Astrophysics Data System (ADS)
Reiner, Jan-Michael; Marthaler, Michael; Braumüller, Jochen; Weides, Martin; Schön, Gerd
2016-09-01
The Jordan-Wigner transformation maps a one-dimensional (1D) spin-1 /2 system onto a fermionic model without spin degree of freedom. A double chain of quantum bits with X X and Z Z couplings of neighboring qubits along and between the chains, respectively, can be mapped on a spin-full 1D Fermi-Hubbard model. The qubit system can thus be used to emulate the quantum properties of this model. We analyze physical implementations of such analog quantum simulators, including one based on transmon qubits, where the Z Z interaction arises due to an inductive coupling and the X X interaction due to a capacitive interaction. We propose protocols to gain confidence in the results of the simulation through measurements of local operators.
Mechanism of spin and charge separation in one-dimensional quantum antiferromagnets
Mudry, C.; Fradkin, E. )
1994-10-15
We reconsider the problem of separation of spin and charge in one-dimensional quantum antiferromagnets. We show that spin and charge separation in one-dimensional strongly correlated systems cannot be described by the slave-boson or fermion representation within any perturbative treatment of the interactions between the slave holons and slave spinons. The constraint of single occupancy must be implemented exactly. As a result the slave fermions and bosons are not part of the physical spectrum. Instead, the excitations that carry the separate spin and charge quantum numbers are solitons. To prove this result, it is sufficient to study the pure spinon sector in the slave-boson representation. We start with a short-range resonating-valence-bond state spin liquid mean-field theory for the frustrated antiferromagnetic spin-1/2 chain. We derive an effective theory for the fluctuations of the Affleck-Marston and Anderson order parameters. We show how to recover the phase diagram as a function of the frustration by treating the fluctuations nonperturbatively.
Entanglement vs. gap for one-dimensional spin systems
Hastings, Matthew; Aharonov, Dorit; Gottesman, Daniel
2008-01-01
We study the relationship between entanglement and spectral gap for local Hamiltonians in one dimension. The area law for a one-dimensional system states that for the ground state, the entanglement of any interval is upper-bounded by a constant independent of the size of the interval. However, the possible dependence of the upper bound on the spectral gap {Delta} is not known, as the best known general upper bound is asymptotically much larger than the largest possible entropy of any model system previously constructed for small {Delta}. To help resolve this asymptotic behavior, we construct a family of one-dimensional local systems for which some intervals have entanglement entropy which is polynomial in 1/{Delta}, whereas previously studied systems had the entropy of all intervals bounded by a constant times log(1/{Delta}).
Spin waves in one-dimensional bicomponent magnonic quasicrystals
NASA Astrophysics Data System (ADS)
Rychły, J.; Kłos, J. W.; Mruczkiewicz, M.; Krawczyk, M.
2015-08-01
We studied a finite Fibonacci sequence of Co and Py stripes aligned side by side and in direct contact with each other. Calculations based on a continuous model, including exchange and dipole interactions, were performed for structures feasible for fabrication and characterization of the main properties of magnonic quasicrystals. We have shown the fractal structure of the magnonic spectrum with a number of magnonic gaps of different widths. Moreover, localization of spin waves in quasicrystals and the existence of surface spin waves in finite quaiscrystal structure is demonstrated.
Spin Interference In Silicon One-Dimensional Rings
NASA Astrophysics Data System (ADS)
Bagraev, N. T.; Galkin, N. G.; Gehlhoff, W.; Klyachkin, L. E.; Malyarenko, A. M.; Shelykh, I. A.
2010-01-01
We present the first findings of the spin transistor effect in the Rashba gate-controlled ring embedded in the p-type self-assembled silicon quantum well that is prepared on the n-type Si (100) surface. Firstly, the amplitude and phase sensitivity of the "0.7ṡ(2 e2/h)" feature of the hole quantum conductance staircase revealed by the quantum point contact inserted in the one of the arms of the double-slit ring are found to result from the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations by varying respectively the value of the external magnetic field and the top-gate bias voltage. Secondly, the "0.7ṡ(2 e2/h)" feature appears to exhibit the fractional form revealed by both the plateuas and steps as a function of the top-gate bias voltage, with the variations of their positions in the external magnetic field.
Jenni, Kevin; Scherthan, Lena; Faus, Isabelle; Marx, Jennifer; Strohm, Cornelius; Herlitschke, Marcus; Wille, Hans-Christian; Würtz, Peter; Schünemann, Volker; Wolny, Juliusz A
2017-07-26
Nuclear inelastic scattering (NIS) experiments have been performed in order to study the vibrational dynamics of the low- and high-spin states of the polynuclear 1D spin crossover compound [Fe(1,2,4-triazole)2(1,2,4-triazolato)](BF4) (1). Density functional theory (DFT) calculations using the functional B3LYP* and the basis set CEP-31G for heptameric and nonameric models of the compound yielded the normal vibrations and electronic energies for high-spin and low-spin isomers of three models differing in the distribution of anionic trz(-) ligands and BF4(-) anions. On the basis of the obtained energies a structural model with a centrosymmetric Fe(trzH)4(trz(-))2 coordination core of the mononuclear unit of the chain is proposed. The obtained distribution of the BF4(-) counteranions in the proposed structure is similar to that obtained on the basis of X-ray powder diffraction studies by Grossjean et al. (Eur. J. Inorg. Chem., 2013, 796). The NIS data of the system diluted to 10% Fe(ii) content in a 90% Zn(ii) matrix (compound (2)) show a characteristic change of the spectral pattern of the low-spin centres, compared to the low-spin phase of the parent Fe(ii) complex (1). DFT calculations reveal that this is caused by a change of the structure of the neighbours of the low-spin centres. The spectral pattern of the high-spin centres in (2) is within a good approximation identical to that of the high-spin Fe(ii) isomer of (1). The inspection of the molecular orbitals of the monomeric model systems of [Fe(trzH)4(trz(-))2] and [Fe(trzH)6], together with calculations of spin transition energies, point towards the importance of an electrostatic effect caused by the negatively charged ligands. This results in the stabilisation of the low-spin state of the complex containing the anionic ligand and shortening of the Fe-N(trz(-)) compared to the Fe-N(trzH) bond in high-spin, but not in low-spin [Fe(trzH)4(trz(-))2].
Pluralism in the critical phenomena of the one-dimensional continuous-spin Ising model
NASA Astrophysics Data System (ADS)
Baker, George A., Jr.
1988-05-01
A concrete example is given which shows that the one-dimensional Ising and Gaussian model universality classes do not exhaust the universality classes of the one-dimensional continuous-spin Ising model. Thus the normal universality hypothesis fails in this simple, readily analyzable model.
Pluralism in the critical phenomena of the one-dimensional continuous-spin Ising model
Baker G.A. Jr.
1988-05-02
A concrete example is given which shows that the one-dimensional Ising and Gaussian model universality classes do not exhaust the universality classes of the one-dimensional continuous-spin Ising model. Thus the normal universality hypothesis fails in this simple, readily analyzable model.
Jiang, Xiao-Ming; Li, Xiao-Guo; Zhang, Ming-Jian; Liu, Zhi-Fa; Liu, Yong; Liu, Jun-Ming; Guo, Guo-Cong
2015-01-01
Exploration of new spin systems with low-dimensional subunits have been of great interest in the past decades due to their interesting physical properties and potential applications in molecular spintronics. Two inorganic supramolecular complexes, (Hg3S2)(FeCl4) and (Hg3S2)(CoCl4), with trigonally aligned 1-D infinite magnetic ∞1(FeCl4)2− or ∞1(CoCl4)2− chains have been prepared by solid-state reactions. They exhibit 3-D long-range spin order with strong field dependence and field induced metamagnetic behavior. The intrachain and interchain magnetic coupling constants were estimated by DFT+U and DFT+U+SOC calculations and the both complexes can be regarded as partially frustrated spin systems. The spin Hamiltonian was constructed, the ground state is proposed to be incommensurate spiral spin order, which differs from the commensurate 120° spin structure ground state of fully frustrated trigonal case by a little canted angle. This study shows that cooperative magnetic ordering induced by geometric frustration can be realized in inorganic supramolecular systems assembled by weak van der Waals’ interactions. PMID:26648133
Oscillatory Dynamics of One-Dimensional Homogeneous Granular Chains
NASA Astrophysics Data System (ADS)
Starosvetsky, Yuli; Jayaprakash, K. R.; Hasan, Md. Arif; Vakakis, Alexander F.
The acoustics of the homogeneous granular chains has been studied extensively both numerically and experimentally in the references cited in the previous chapters. This chapter focuses on the oscillatory behavior of finite dimensional homogeneous granular chains. It is well known that normal vibration modes are the building blocks of the vibrations of linear systems due to the applicability of the principle of superposition. One the other hand, nonlinear theory is deprived of such a general superposition principle (although special cases of nonlinear superpositions do exist), but nonlinear normal modes ‒ NNMs still play an important role in the forced and resonance dynamics of these systems. In their basic definition [1], NNMs were defined as time-periodic nonlinear oscillations of discrete or continuous dynamical systems where all coordinates (degrees-of-freedom) oscillate in-unison with the same frequency; further extensions of this definition have been considered to account for NNMs of systems with internal resonances [2]...
Acoustics of One-Dimensional Homogeneous Granular Chains
NASA Astrophysics Data System (ADS)
Starosvetsky, Yuli; Jayaprakash, K. R.; Hasan, Md. Arif; Vakakis, Alexander F.
The Chapter 1 provided a brief glimpse of the general ordered granular chain/lattices, their subtle features and the intricacies associated with their analysis. By now it should be clear that this class of highly-inhomogeneous and discontinuous systems poses new challenges in the form of strongly nonlinear behavior, bead separations, and twice (at most) differentiable interaction potential. It follows that the traditional analytical methodologies may need to be modified to effectively address these challenges. To begin with, we consider the simplest case of the homogeneous granular chains, wherein, the particles are identical and are perfectly in contact (no gaps) initially. We consider the case of both the uncompressed (strongly nonlinear) and the pre-compressed (weakly nonlinear) chains and elucidate the striking differences between their dynamical behaviors. In the latter case, the long wave/continuum approximation is invoked in this analysis thus precluding any bead separations. A landmark discovery in this class of systems is the realization of the solitary wave propagation [1-3]. These waves are highly localized spatially symmetric disturbances which propagate in the nonlinear medium. In general, it is well known that the linear nondispersive waves have a characteristic wave speed (property of the medium), and a disturbance of any amplitude or waveform propagates at the same speed undistorted. In contrast, the propagation velocity of the solitary waves in a nonlinear medium is a function of the wave amplitude (a general nonlinear behavior) and the physical properties of the medium. It is worth noting that any arbitrary disturbance set in motion in a homogeneous granular chain eventually disintegrates into a train of the solitary waves of varying amplitudes propagating at the proportional velocities (higher the amplitude, higher the propagation velocity). Although these waves are called solitary waves, they do not necessarily conform to the definition [4
A one-dimensional chain state of vortex matter
NASA Astrophysics Data System (ADS)
Bending, Simon
2003-03-01
The dependence of the vortex ground state on magnetic field direction in the highly anisotropic Bi_ 2Sr_ 2CaCu_ 2O_ 8+d (BSCCO) superconductor is a topic of considerable current interest. With the magnetic field tilted away from the high symmetry c-axis it is expected to consist of co-existing orthogonal 6-fold Abrikosov pancake vortex (PV) and rhombic Josephson vortex (JV) lattices. Furthermore it has been shown recently that small displacements of PVs driven by the underlying JV supercurrents can lead to an attractive interaction between these two crossing' lattices and can give rise to a very rich variety of composite lattice structures. We report here the use of high resolution scanning Hall probe microscopy (SHPM) to directly probe the static and dynamic properties of these structures in BSCCO single crystals under independently applied H_ c and H_ // fields. At very low c-axis fields we observe a novel 1D vortex chain state where all pancake vortex stacks become trapped on underlying stacks of Josephson vortices. The remarkable dynamic properties of this system of interacting orthogonal vortex lattices will be described. In particular it will be shown how one sub-lattice can be used to manipulate the other with the exciting potential for building novel flux logic and flux amplifier devices. In addition the existence of 1D vortex chains explains many of the features observed in the magnetisation of HTS under strongly tilted magnetic fields. The dependence of vortex structures on in-plane field is in good quantitative agreement with theoretical predictions, yielding an almost temperature-independent anisotropy parameter of g=640+/-25 in the range 77-85K. We directly confirm that the PV/JV attraction arises from small PV displacements in the presence of JV supercurrents. In addition we demonstrate how the presence of quenched disorder leads to indirect JV pinning via interactions with weakly pinned PV stacks, and develop a theoretical model for this phenomenon
Elastic interaction among transition metals in one-dimensional spin-crossover solids
NASA Astrophysics Data System (ADS)
Boukheddaden, K.; Miyashita, S.; Nishino, M.
2007-03-01
We present an exact examination of a one-dimensional (1D) spin-phonon model describing the thermodynamical properties of spin-crossover (SC) solids. This model has the advantage of giving a physical mechanism for the interaction between the SC units. The origin of the interaction comes from the fact that the elastic constant of the spring linking two atoms depends on their electronic states. This leads to local variation of the elastic constant. Up to now, all the statistical studies of this model have been performed in the frame of the mean-field (MF) approach, which is not adequate to describe 1D systems with short-range interactions. An alternative method, based on the variational approach and taking into account the short-range correlations between neighboring molecules, was also suggested, but it consists in an extension of the previous MF approximation. Here, we solve exactly this Hamiltonian in the frame of classical statistical mechanics using the transfer-matrix technique. The temperature dependence of the high spin fraction and that of the total energy are obtained analytically. Our results clearly show that there is a clear tendency to a sharp transition when we tune the elastic constants adequately, which indicates that first-order phase transition takes place at higher dimensions. In addition, we demonstrate the existence of an interesting isomorphism between the present model and Ising model under effective interaction and effective ligand field energy, in which both depend linearly on temperature and both come from the phonon contribution. We have also studied the effect of the pressure (the tension) on the thermodynamical properties of the high spin (HS) fraction and have found a nontrivial pressure effect that while for weak tension values, the low spin state is stabilized for the pressure above a threshold value, it enhances the interaction between the HS states. Finally, we have also introduced elastic interactions between the chains. Treating
Competition between spin and charge order in a one-dimensional lattice
NASA Astrophysics Data System (ADS)
Talebi, Amir Hossein; Davoudi, Bahman; Rahimitabar, M. Reza
2017-10-01
In this paper, we study the presence of competing instabilities in one-dimensional (1D) extended Hubbard model (EHM). Using the extended two-particle self-consistent approximation (ETPSC), we derive the density and interaction dependent crossover diagram for spin and charge density wave fluctuations at arbitrary wave number. We determine the phase transitions of the system by means of spin and charge susceptibilities. We draw the phase diagram which separates different phases of the model for several effective particle densities.
NASA Astrophysics Data System (ADS)
Jen, H. H.; Yip, S.-K.
2017-05-01
Spin-incoherent Luttinger liquid (SILL) is a different universal class from the Luttinger liquid. This difference results from the spin incoherence of the system when the thermal energy of the system is higher than the spin excitation energy. We consider one-dimensional spin-1 Bose gas in the SILL regime and investigate its spin-dependent many-body properties. In Tonks-Girardeau limit, we are able to write down the general wave functions in a harmonic trap. We numerically calculate the spin-dependent (spin-plus, minus, and zero) momentum distributions in the sector of zero magnetization which allows us to demonstrate the most significant spin-incoherent feature compared to the spinless or spin-polarized case. In contrast to the spinless Bose gas, the momentum distributions are broadened and in the large momentum limit follow the same asymptotic 1 /p4 dependence but with reduced coefficients. While the density matrices and momentum distributions differ between different spin components for small N , at large N they approach each other. We show these by analytic arguments and numerical calculations up to N =16 .
Rufo, Sabrina; Mendonça, Griffith; Plascak, J A; de Sousa, J Ricardo
2013-09-01
The ground-state properties of the quasi-one-dimensional spin-1/2 antiferromagnetic Heisenberg model is investigated by using a variational method. Spins on chains along the x direction are antiferromagnetically coupled with exchange J>0, while spins between chains in the y direction are coupled either ferromagnetically (J' < 0) or antiferromagnetically (J' > 0). The staggered and the colinear antiferromagnetic magnetizations are computed and their dependence on the anisotropy parameter λ=|J'|/J is analyzed. It is found that an infinitesimal interchain coupling parameter is sufficient to stabilize a long-range order with either a staggered magnetization m_{s} (J' > 0) or a colinear antiferromagnetic magnetization m_{caf} (J' < 0), both behaving as ≃λ¹/² for λ → 0.
Quantum distance and the Euler number index of the Bloch band in a one-dimensional spin model.
Ma, Yu-Quan
2014-10-01
We study the Riemannian metric and the Euler characteristic number of the Bloch band in a one-dimensional spin model with multisite spins exchange interactions. The Euler number of the Bloch band originates from the Gauss-Bonnet theorem on the topological characterization of the closed Bloch states manifold in the first Brillouin zone. We study this approach analytically in a transverse field XY spin chain with three-site spin coupled interactions. We define a class of cyclic quantum distance on the Bloch band and on the ground state, respectively, as a local characterization for quantum phase transitions. Specifically, we give a general formula for the Euler number by means of the Berry curvature in the case of two-band models, which reveals its essential relation to the first Chern number of the band insulators. Finally, we show that the ferromagnetic-paramagnetic phase transition in zero temperature can be distinguished by the Euler number of the Bloch band.
Quantum spin fluctuations in quasi-one-dimensional chlorine-bridged platinum complexes
NASA Astrophysics Data System (ADS)
Wei, Xing; Donohoe, Robert J.; Wang, Wen Z.; Bishop, Alan R.; Gammel, Jan T.
1997-12-01
We report experimental and theoretical studies of spin dynamic process in the quasi-one-dimensional chlorine- bridged platinum complex, [PtII(en)2][PtIV(en)2Cl2](ClO4)4, where en equals ethylenediamine, C2N2H8. The process manifests itself in collapsing of the hyperfine and superhyperfine structures in the electron spin resonance spectrum and non-statistical distribution of spectral weight of the Pt isotopes. More surprisingly, it is activated only at temperatures below 6 K. We interpret the phenomenon in terms of quantum tunneling of the electronic spin in a strong electron-electron and electron-phonon coupling regime. This is modeled using a non-adiabatic many-body approach, in which polarons and solitons represent local spin-Peierls regions in a strongly disproportional charge- density-wave background and display intriguing spin-charge separation in the form of pinned charge and tunneling spin fluctuations.
Entanglement in the quantum one-dimensional integer spin S Heisenberg antiferromagnet
NASA Astrophysics Data System (ADS)
Lima, L. S.
2017-10-01
We use the modified spin wave theory of Takahashi to study the entanglement entropy in the quantum one-dimensional integer spin Heisenberg antiferromagnet. We calculate the entanglement entropy of this spin system that is well known to be a quantum wire, in the classical limit (N → ∞). We obtain a decreasing the entanglement entropy with the temperature and we obtain none change in the entanglement in the point Δ = 1 at T = 0 where the system presents a quantum phase transition from a gapless phase in the spectrum Δ < 1 to a gapped phase Δ ≥ 1.
Implementation of one-dimensional quantum walks on spin-orbital angular momentum space of photons
Zhang Pei; Liu Ruifeng; Li Hongrong; Li Fuli; Liu Biheng; Guo Guangcan
2010-05-15
Photons can carry spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used to realize a qubit system and a high-dimension system, respectively. This spin-orbital system is very suitable for implementing one-dimensional discrete-time quantum random walks. We propose a simple scheme of quantum walks on the spin-orbital angular momentum space of photons, where photons walk on the infinite OAM space controlled by their SAM. By employing the recent invention of an optical device, the so-called 'q-plate', our scheme is more simple and efficient than others because there is no Mach-Zehnder interferometer in the scheme.
Entanglement dynamics of one-dimensional driven spin systems in time-varying magnetic fields
Alkurtass, Bedoor; Sadiek, Gehad; Kais, Sabre
2011-08-15
We study the dynamics of nearest-neighbor entanglement for a one-dimensional spin chain with a nearest-neighbor time-dependent Heisenberg coupling J(t) between the spins in the presence of a time-dependent external magnetic field h(t) at zero and finite temperatures. We consider different forms of time dependence for the coupling and magnetic field: exponential, hyperbolic, and periodic. Solving the system numerically, we examined the system-size effect on the entanglement asymptotic value. It was found that, for a small system size, the entanglement starts to fluctuate within a short period of time after applying the time-dependent coupling. The period of time increases as the system size increases and disappears completely as the size goes to infinity. Testing the effect of the transition constant for an exponential or hyperbolic coupling showed a direct impact on the asymptotic value of the entanglement; the larger the constant is, the lower the asymptotic value and the more rapid decay of entanglement are, which confirms the nonergodic character of the system. We also found that, when J(t) is periodic, the entanglement shows a periodic behavior with the same period, which disappears upon applying periodic magnetic field with the same frequency. Solving the case J(t)={lambda}h(t), for constant {lambda}, exactly, we showed that the time evolution and asymptotic value of entanglement are dictated solely by the parameter {lambda}=J/h rather than the individual values of J and h, not only when they are time independent and at zero temperature, but also when they are time dependent but proportional at zero and finite temperatures for all degrees of anisotropy.
NASA Astrophysics Data System (ADS)
Wang, Ji-Guo; Yang, Shi-Jie
2017-05-01
We study a model to realize the long-distance correlated tunneling of ultracold bosons in a one-dimensional optical lattice chain. The model reveals the behavior of a quantum Newton's cradle, which is the perfect transfer between two macroscopic quantum states. Due to the Bose enhancement effect, we find that the resonantly tunneling through a Mott domain is greatly enhanced.
Spin wave localization in one-dimensional magnonic microcavity comprising yttrium iron garnet
Kanazawa, Naoki; Goto, Taichi Inoue, Mitsuteru
2014-08-28
We demonstrate the localization of magnetostatic surface waves, i.e., spin waves, in a one-dimensional magnonic microcavity substantialized with periodical conductivity modulation. The narrow localized state is observed inside band gaps and is responsible for a sharp transmission peak. The experimental results strongly agree with the theoretical prediction made with the shape magnetic anisotropy of the propagating medium composed of yttrium iron garnet taken into account.
The paramagnetic properties of one-dimensional spin-1 single-ion anisotropic ferromagnet
NASA Astrophysics Data System (ADS)
Wang, Hai-Jun; Chen, Yuan; Fu, Liang-Jie; Lin, Rui-Na; Song, Chuang-Chuang
2009-06-01
One-dimensional single-ion anisotropic ferromagnet with spin-1 is investigated by means of Green's function treatment in this paper. The model Hamiltonian includes a Heisenberg ferromagnetic term, an external magnetic field, and a second-order single-ion anisotropy. The magnetic properties of the system are treated by the random phase approximation for the exchange interaction term and the Anderson-Callen approximation for the anisotropy term. Our paramagnetic results are in agreement with the other theoretical results.
Dimerized ground state in the one-dimensional spin-1 boson Hubbard model
Apaja, Vesa; Syljuaasen, Olav F.
2006-09-15
We have investigated the one-dimensional spin-1 boson Hubbard model with antiferromagnetic interactions using quantum Monte Carlo methods. We obtain the shapes of the two lowest Mott lobes and show that the ground state within the lowest Mott lobe is dimerized. The results presented here are relevant for optically trapped antiferromagnetic spin-1 bosons. An experimental signature of the dimerized ground state is modulated Bragg peaks in the noise distribution of the atomic cloud obtained after switching off the trap. These Bragg peaks are located at wave vectors corresponding to half-integer multiples of the reciprocal wave vector of the optical lattice.
Strongly-coupled Josephson junction array for simulation of frustrated one-dimensional spin models
NASA Astrophysics Data System (ADS)
Zhou, Zhengwei; Du, Lianghui; Zhou, Xingxiang; Han, Yongjian; Guo, Guangcan
2013-03-01
We study the capacitance-coupled Josephson-junction array beyond the small-coupling limit. We find that, when the scale of the system is large, its Hamiltonian can be obtained without the small-coupling approximation and the system can be used to simulate strongly frustrated one-dimensional Ising spin problems. To engineer the system Hamiltonian for an ideal theoretical model, we apply a dynamical-decoupling technique to eliminate undesirable couplings in the system. Using a six-site junction array as an example, we numerically evaluate the system to show that it exhibits important characteristics of the frustrated spin model.
Motion of solitons in one-dimensional spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wen, Lin; Sun, Q.; Chen, Yu; Wang, Deng-Shan; Hu, J.; Chen, H.; Liu, W.-M.; JuzeliÅ«nas, G.; Malomed, Boris A.; Ji, An-Chun
2016-12-01
Solitons play a fundamental role in the dynamics of nonlinear excitations. Here we explore the motion of solitons in one-dimensional Bose-Einstein condensates subjected to a spin-orbit coupling (SOC). We demonstrate that the spin dynamics of solitons is governed by a nonlinear Bloch equation. The spin dynamics affects the orbital motion of solitons leading to spin-orbit effects in the dynamics of macroscopic quantum objects (mean-field solitons). The latter perform oscillations with a frequency determined by the SOC, Raman coupling, and intrinsic nonlinearity. These findings reveal unique features of solitons affected by the SOC, which are confirmed by analytical considerations and numerical simulations of the underlying Gross-Pitaevskii equations.
Thermal transport in a one-dimensional Z2 spin liquid
NASA Astrophysics Data System (ADS)
Metavitsiadis, Alexandros; Brenig, Wolfram
2017-07-01
We study the dynamical thermal conductivity of the Kitaev spin model on a two-leg ladder. In contrast to the majority of conventional one-dimensional spin systems, we show the ladder to exhibit no ballistic channel and a zero-frequency pseudogap. This is a direct consequence of the fractionalization of spins into mobile Majorana matter and a static Z2 gauge field, which acts as an emergent thermally activated disorder. Our finding rests on complementary calculations of the current correlation function, comprising a phenomenological mean-field treatment of thermal gauge fluctuations, a complete summation over all gauge sectors, as well as exact diagonalization of the original spin model. The results will also be contrasted against the conductivity discarding gauge fluctuations.
Different spin textures in one-dimensional electronic bands on Si(5 5 3)-Au surface
NASA Astrophysics Data System (ADS)
Krawiec, M.; Kopciuszyński, M.; Zdyb, R.
2016-06-01
A doublet of one-dimensional metallic bands on Au-stabilized Si(5 5 3) surface features different splitting due to the spin-orbit interaction. Density functional theory calculations reveal the origin of unequal magnitude of the splitting. Furthermore, different orientations of spin polarizations, almost perpendicular to each other, in both spin-orbit split bands are discovered. These observations are consistent with the Rashba effect and induced electric field in the system with out-of-plane and in-plane components. The results of calculations are confirmed by spin- and angle-resolved photoelectron spectroscopy measurements. The Si(5 5 3)-Au surface appears as a unique 1D Rashba system.
Viet, Dao Xuan; Kawamura, Hikaru
2010-08-27
We study the issue of the spin-chirality decoupling or coupling in the ordering of the Heisenberg spin glass by performing large-scale Monte Carlo simulations on a one-dimensional Heisenberg spin-glass model with a long-range power-law interaction up to large system sizes. We find that the spin-chirality decoupling occurs for an intermediate range of the power-law exponent. Implications to the corresponding d-dimensional short-range model are discussed.
Spin-disordered quantum phases in a quasi-one-dimensional triangular lattice
NASA Astrophysics Data System (ADS)
Yoshida, Yukihiro; Ito, Hiroshi; Maesato, Mitsuhiko; Shimizu, Yasuhiro; Hayama, Hiromi; Hiramatsu, Takaaki; Nakamura, Yuto; Kishida, Hideo; Koretsune, Takashi; Hotta, Chisa; Saito, Gunzi
2015-08-01
Large quantum fluctuations drive the spins in solids into magnetically disordered phases that are not simply paramagnetic. This class of system includes the valence bond crystals and quantum spin liquids, in which spin singlets--the basic unit of entangled pairs of spins--form solids and liquids, respectively. In both phases, geometrical frustration is expected to play a role. So far, very few candidate quantum-spin-liquid materials have been found, including an organic Mott insulator, κ-(ET)2Cu2(CN)3, which is based on a regular triangular lattice. Here, we report a material, κ-(ET)2B(CN)4, with different geometry--a highly distorted quasi-one-dimensional triangular lattice. The magnetic susceptibility follows that of the spin-1/2 Heisenberg model on this distorted lattice. The material sustains a magnetically disordered Mott insulating state with enhanced quantum fluctuations over a wide temperature range, and undergoes a transition into a spin-gapped phase at 5 K.
Regular phases of quasi-one-dimensional spin systems: Classification and imprints on diffraction
NASA Astrophysics Data System (ADS)
Milivojević, Marko; Lazić, Nataša; Vuković, Tatjana; Damnjanović, Milan
2015-10-01
Referring to the propulsive field of low-dimensional magnetism, the paper discusses the foundation and principles of exploitation of the spin line groups, thus establishing a base for full implementation of the symmetry in further studies of frustrated quasi-one-dimensional magnetics. The classification of the symmetry-allowed magnetic phases reveals full diversity of the complex helimagnets, tilted along a singled-out direction, as well as within the cross sections perpendicular to it. The neutron diffraction amplitudes are exhaustively calculated for all the possible spin arrangements, providing experimentally verifiable fingerprints of the particular order of the spin structures. A recent prediction of the gate-voltage-dependent phases of 13C carbon nanotubes serves as an illustration of the introduced concepts and their applications in the ground state determination.
Terahertz spin-wave waveguides and optical magnonics in one-dimensional NiO nanorods
NASA Astrophysics Data System (ADS)
Patil, Ranjit A.; Su, Chiung-Wu; Chuang, Chin-Jung; Lai, Chien-Chih; Liou, Yung; Ma, Yuan-Ron
2016-06-01
The two-magnon (2M) spin waves with a magnon frequency of 43 THz, generated by a polarized laser, were first observed in one-dimensional (1D) NiO nanorods. The 1D NiO nanorods of ~700 nm length, which have perfectly in-plane antiferromagnetic spins lying on the (200) and (100) faces, are the smallest spin-wave waveguides. Due to the magneto-optical Faraday effect (MOFE), the significant change in the Faraday intensity can show the 2M information in the NiO nanorods. There are only two 2M-on and 2M-off states at various applied alternating-current magnetic fields and laser-incident angles, which make the 1D NiO nanorods excellent optical nanomagnonics.The two-magnon (2M) spin waves with a magnon frequency of 43 THz, generated by a polarized laser, were first observed in one-dimensional (1D) NiO nanorods. The 1D NiO nanorods of ~700 nm length, which have perfectly in-plane antiferromagnetic spins lying on the (200) and (100) faces, are the smallest spin-wave waveguides. Due to the magneto-optical Faraday effect (MOFE), the significant change in the Faraday intensity can show the 2M information in the NiO nanorods. There are only two 2M-on and 2M-off states at various applied alternating-current magnetic fields and laser-incident angles, which make the 1D NiO nanorods excellent optical nanomagnonics. Electronic supplementary information (ESI) available: Cubic crystal structure and Raman scattering of 1D NiO nanorods. See DOI: 10.1039/c6nr02531e
NASA Astrophysics Data System (ADS)
Li, Jian; Zheng, Dong-qin; Zhong, Wei-rong
2015-10-01
In order to investigate the thermal transport in one-dimensional (1D) superlattice and quasicrystal chains, the simple harmonic-oscillator model and the C60 chains model, are studied through non-equilibrium molecular dynamics simulation. In the simple harmonic-oscillator model, we construct a simple periodic harmonic-oscillator chain by using two different stiffness coefficients alternatively. It is found that its thermal conductivity is smaller than in non-periodic chains, no matter which stiffness coefficient is used in the non-periodic chains. In order to test if this is true in a real material structure, a superlattice C60 chain is constructed by connecting perfect and defective C60 alternatively. The calculation outcome of the C60 chains coincides with the results of the simple harmonic-oscillator model, that the thermal conductivity of the superlattice C60 chain is smaller than that of perfect and defective crystal C60 chains. Besides this, we also studied the thermal transport properties of the quasicrystal C60 chain, which consists of a random defective C60 molecular structure. It is found that the thermal conductivity of the quasicrystal structure is far less than that of the crystal and superlattice chains. The phonon spectra of the perfect, defective and superlattice C60 chain are provided to give corresponding supports. Our results also propose a controllable method for the thermal management in nanoscale materials.
Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron
NASA Astrophysics Data System (ADS)
Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco
2016-12-01
The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor.
Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron.
Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco
2016-12-14
The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor.
Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron
Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco
2016-01-01
The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor. PMID:27966598
Standing spin waves and solitons in a quasi-one-dimensional spiral structure
Kiselev, V. V. Raskovalov, A. A.
2013-02-15
On the basis of the sine-Gordon model, we calculated the absorption spectrum for the external pump power in a quasi-one-dimensional spiral structure of easy-plane magnets without the inversion center in the presence of a static magnetic field perpendicular to the magnetic spiral axis. It is shown that these data can be used for determining the material constants of the magnet and diagnostics of spin waves and solitons in its spiral structure. The possibility of using magnetooptical methods to observe local translations of the spiral structure during formation and motion of solitons in it is discussed.
Third-neighbor correlators of a one-dimensional spin-1/2 Heisenberg antiferromagnet.
Sakai, Kazumitsu; Shiroishi, Masahiro; Nishiyama, Yoshihiro; Takahashi, Minoru
2003-06-01
We exactly evaluate the third-neighbor correlator S(z)(j)S(z)(j+3) and all the possible nonzero correlators S(alpha)(j)S(beta)(j+1)S(gamma;)(j+2)S(delta)(j+3) of the one-dimensional spin-1/2 Heisenberg XXX antiferromagnet in the ground state without magnetic field. All the correlators are expressed in terms of certain combinations of logarithm ln 2, the Riemann zeta function zeta(3), zeta(5) with rational coefficients. The results accurately coincide with the numerical ones obtained by the density-matrix renormalization group method and the numerical diagonalization.
Spin polarization in one dimensional ring with Rashba spin-orbit interaction
Liu, Duan-Yang; Xia, Jian-Bai
2014-01-28
We investigate theoretically spin polarization in a square AB ring and in a circular AB ring with the Rashba spin-orbit interaction (RSOI) and the magnetic flux. It is shown that in the presence of both the RSOI and the perpendicular magnetic field, the AB rings can work as a spin polarizer, and the spin polarization transport can be modulated by the values of the system parameters. In addition, we find that the square ring is more suitable for a spin polarizer due to its higher stability.
NASA Astrophysics Data System (ADS)
Montorsi, Arianna; Dolcini, Fabrizio; Iotti, Rita C.; Rossi, Fausto
2017-06-01
The low energy behavior of a huge variety of one-dimensional interacting spinful fermionic systems exhibits spin-charge separation, described in the continuum limit by two sine-Gordon models decoupled in the charge and spin channels. Interaction is known to induce, besides the gapless Luttinger liquid phase, eight possible gapped phases, among which are the Mott, Haldane, charge-/spin-density, and bond-ordered wave insulators, and the Luther Emery liquid. Here we prove that some of these physically distinct phases have nontrivial topological properties, notably the presence of degenerate protected edge modes with fractionalized charge/spin. Moreover, we show that the eight gapped phases are in one-to-one correspondence with the symmetry-protected topological (SPT) phases classified by group cohomology theory in the presence of particle-hole symmetry P. The latter result is also exploited to characterize SPT phases by measurable nonlocal order parameters which follow the system evolution to the quantum phase transition. The implications on the appearance of exotic orders in the class of microscopic Hubbard Hamiltonians, possibly without P symmetry at higher energies, are discussed.
One-Dimensional Edge States with Giant Spin Splitting in a Bismuth Thin Film
NASA Astrophysics Data System (ADS)
Takayama, A.; Sato, T.; Souma, S.; Oguchi, T.; Takahashi, T.
2015-02-01
To realize a one-dimensional (1D) system with strong spin-orbit coupling is a big challenge in modern physics, since the electrons in such a system are predicted to exhibit exotic properties unexpected from the 2D or 3D counterparts, while it was difficult to realize genuine physical properties inherent to the 1D system. We demonstrate the first experimental result that directly determines the purely 1D band structure by performing spin-resolved angle-resolved photoemission spectroscopy of Bi islands on a silicon surface that contains a metallic 1D edge structure with unexpectedly large Rashba-type spin-orbit coupling suggestive of the nontopological nature. We have also found a sizable out-of-plane spin polarization of the 1D edge state, consistent with our first-principles band calculations. Our result provides a new platform to realize exotic quantum phenomena at the 1D edge of the strong spin-orbit-coupling systems.
Phase separation of trapped spin-imbalanced Fermi gases in one-dimensional optical lattices
Heidrich-Meisner, F.; Orso, G.; Feiguin, A. E.
2010-05-15
We calculate the density profiles of a trapped spin-imbalanced Fermi gas with attractive interactions in a one-dimensional optical lattice, using both the local-density approximation (LDA) and density-matrix renormalization-group (DMRG) simulations. Based on the exact equation of state obtained by Bethe ansatz, the LDA predicts that the gas phase separates into shells with a partially polarized core and fully paired wings, the latter occurring below a critical spin polarization. This behavior is also seen in numerically exact DMRG calculations at sufficiently large particle numbers. We show that, unlike in the continuum case, the critical polarization is a nonmonotonic function of the interaction strength and vanishes in the limit of large interactions.
NASA Astrophysics Data System (ADS)
Kawakami, Takuto; Hu, Xiao
2016-01-01
We investigate one-dimensional (1D) Majorana bound states (MBSs) realized in terms of the helical edge states of a 2D quantum spin-Hall insulator in a heterostructure with a superconducting substrate and two ferromagnetic insulators (FIs). By means of Bogoliubov-de Gennes approach we demonstrate that there is a helical spin texture in the MBS wave function with a pitch proportional to the Fermi momentum. Moreover, simultaneous detection on local density of states by scanning tunneling microscopy and spectroscopy at a position close to one FI edge and at the midpoint between the two FIs can not only map out the energy spectrum ±E cos(ϕ/2) where ϕ is the relative angle between the magnetizations of two FIs, but also prove experimentally that the two quasiparticle excitations do not mix with each other as protected by the parity conservation associated with the MBSs.
Hidden one-dimensional spin modulation in a three-dimensional metal.
Feng, Yejun; Wang, Jiyang; Palmer, A; Aguiar, J A; Mihaila, B; Yan, J-Q; Littlewood, P B; Rosenbaum, T F
2014-06-18
Pressure can transform a transparent material into an opaque one, quench the moments in a magnet and force solids to flow like liquids. At 15 GPa, the pressure found 500 km below the earth's surface, the semiconductors silicon and germanium superconduct. Yet, at this same pressure, we show here that the magnetism in metallic GdSi remains completely robust even as it shrinks by one-seventh of its volume. Non-resonant X-ray magnetic diffraction in a specially designed diamond anvil cell, combined with band structure calculations, reveal the stability of the incommensurate spin density wave, which can be traced to a persistently nested portion of the Fermi surface that becomes increasingly one-dimensional under pressure. A cooperative interaction between nested, itinerant spins and local magnetic moments provides the organizing principle for the modulated magnetic order, salient both for its insights into the role of topology in ordered states and its potential functionality.
NASA Astrophysics Data System (ADS)
Chiruta, Daniel; Linares, Jorge; Miyashita, Seiji; Boukheddaden, Kamel
2014-05-01
In order to explain clearly the role of the open boundary conditions (OBCs) on phase transition in one dimensional system, we consider an Ising model with both short-range (J) and long-range (G) interactions, which has allowed us to study the cooperative nature of spin-crossover (SCO) materials at the nanometer scale. At this end, we developed a transfer-matrix method for one-dimensional (1D) SCO system with free boundary conditions, and we give numerical evidences for how the thermal spin transition curves vary as a function of the physical parameters (J, G) or an applied pressure. Moreover for OBCs case, we have derived the bulk, surface and finite-size contributions to the free energy and we have investigated the variation of these energies as function of J and system size. We have found that the surface free energy behaves like J⟨σ⟩2, where ⟨σ⟩ is the average magnetization per site. Since the properties of the nanometric scale are dramatically influenced by the system's size (N), our analytical outcomes for the size dependence represent a step to achieve new characteristic of the future devices and also a way to find various novel properties which are absent in the bulk materials.
Chiruta, Daniel; Linares, Jorge E-mail: miya@spin.phys.s.u-tokyo.ac.jp; Boukheddaden, Kamel; Miyashita, Seiji E-mail: miya@spin.phys.s.u-tokyo.ac.jp
2014-05-21
In order to explain clearly the role of the open boundary conditions (OBCs) on phase transition in one dimensional system, we consider an Ising model with both short-range (J) and long-range (G) interactions, which has allowed us to study the cooperative nature of spin-crossover (SCO) materials at the nanometer scale. At this end, we developed a transfer-matrix method for one-dimensional (1D) SCO system with free boundary conditions, and we give numerical evidences for how the thermal spin transition curves vary as a function of the physical parameters (J, G) or an applied pressure. Moreover for OBCs case, we have derived the bulk, surface and finite-size contributions to the free energy and we have investigated the variation of these energies as function of J and system size. We have found that the surface free energy behaves like J〈σ〉{sup 2}, where 〈σ〉 is the average magnetization per site. Since the properties of the nanometric scale are dramatically influenced by the system's size (N), our analytical outcomes for the size dependence represent a step to achieve new characteristic of the future devices and also a way to find various novel properties which are absent in the bulk materials.
Image-potential-induced spin-orbit interaction in one-dimensional electron systems
NASA Astrophysics Data System (ADS)
Gindikin, Yasha; Sablikov, Vladimir A.
2017-01-01
We study the spin-orbit interaction effects in a one-dimensional electron system that result from the image charges in a nearby metallic gate. The nontrivial property of the image-potential-induced spin-orbit interaction (iSOI) is that it directly depends on the electron density because of which a positive feedback arises between the electron density and the iSOI magnitude. As a result, the system becomes unstable against the density fluctuations under certain conditions. In addition, the iSOI contributes to the electron-electron interaction giving rise to strong changes in electron correlations and collective excitation spectra. We trace the evolution of the spectrum of the collective excitations and their spin-charge structures with the change in the iSOI parameter. One out of two collective modes softens as the iSOI amplitude grows to become unstable at its critical value. Interestingly, this mode evolves from a pure spin excitation to a pure charge one. At the critical point its velocity turns to zero together with the charge stiffness.
Spin-orbit coupling in quasi-one-dimensional Wigner crystals
NASA Astrophysics Data System (ADS)
Kornich, Viktoriia; Pedder, Christopher J.; Schmidt, Thomas L.
2017-01-01
We study the effect of Rashba spin-orbit coupling (SOC) on the charge and spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal. As electrons in a quasi-1D Wigner crystal can move in the transverse direction, SOC cannot be gauged away in contrast to the pure 1D case. We show that for weak SOC, a partial gap in the spectrum opens at certain ratios between the density of electrons and the inverse Rashba length. We present how the low-energy branch of charge degrees of freedom deviates due to SOC from its usual linear dependence at small wave vectors. In the case of strong SOC, we show that the spin sector of a Wigner crystal cannot be described by an isotropic antiferromagnetic Heisenberg Hamiltonian anymore and that instead the ground state of neighboring electrons is mostly a triplet state. We present a new spin sector Hamiltonian and discuss the spectrum of a Wigner crystal in this limit.
NASA Astrophysics Data System (ADS)
Kurokawa, Shu; Yamamoto, Daisuke; Hirashige, Kenji; Sakai, Akira
2016-04-01
We found one-dimensional chains of carbon particles on Ag(111) and Au(111) surfaces after the deposition of carbon using an arc-plasma gun (APG). The observed periodicity of the chains on Ag(111) was 0.58-0.6 nm. Ex situ Fourier transform infrared (FT-IR) spectroscopy indicated two peaks at 1343 and 1406 cm-1. The simulation of the infrared spectrum for a tetramer of C20 fullerenes showed good agreement with the experimental result. From these findings, we propose the formation of chains of C20 fullerenes as the most probable explanation of the results of both scanning tunneling microscopy (STM) and FT-IR spectroscopy.
Coulomb blockade and transport in a chain of one-dimensional quantum dots.
Fogler, Michael M; Malinin, Sergey V; Nattermann, Thomas
2006-09-01
A long one-dimensional wire with a finite density of strong random impurities is modeled as a chain of weakly coupled quantum dots. At low temperature T and applied voltage V its resistance is limited by breaks: randomly occurring clusters of quantum dots with a special length distribution pattern that inhibit the transport. Because of the interplay of interaction and disorder effects the resistance can exhibit T and V dependences that can be approximated by power laws. The corresponding two exponents differ greatly from each other and depend not only on the intrinsic electronic parameters but also on the impurity distribution statistics.
Quantum spin transistor with a Heisenberg spin chain
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
Electronic spin polarization in the Majorana bound state in one-dimensional wires
NASA Astrophysics Data System (ADS)
Val'kov, V. V.; Aksenov, S. V.
2017-10-01
We have studied the effect of magnetic field and disorder on the electronic z-spin polarization at the ends of the one-dimensional wire with strong Rashba spin-orbit coupling deposited on an s-wave superconductor. It was shown that in the topologically nontrivial phase the polarization as well as the energy of the Majorana bound state oscillate as a function of the magnetic field. Despite being substantially nonzero in the low transversal and longitudinal fields the polarization at one of the wire's ends is significantly suppressed at a certain range of the magnitudes and angles of the canted magnetic field. Thus, in this case the polarization cannot be regarded as a local order parameter. However, the sum of the absolute values of the polarization at both ends remains significantly nonzero. It was demonstrated that Anderson disorder does not seriously affect observed properties but leads to the appearance of the additional areas with weak spin polarization at the high magnetic fields.
Marginal Paramagnetic State of a One-Dimensional Half-Filled Alternating Chain in (TTM-TTP)AuI 2
NASA Astrophysics Data System (ADS)
Kawamoto, Tadashi; Mori, Takehiko; Yamamoto, Takashi; Tajima, Hiroyuki; Misaki, Yohji; Tanaka, Kazuyoshi
2000-12-01
(TTM-TTP)AuI2(TTM-TTP: 2,5-bis[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene)has a dimerized structurealong the donor stacking direction,and shows semiconducting behavior below room temperature.ESR, static magnetic susceptibility, and optical reflectanceof this salt have been measured to investigatethe spin state and the electronic correlation.The ESR signal has been observed from room temperature to 3 K,and the spin susceptibility shows paramagnetic behavior with arapid decrease below 10 K.The static magnetic susceptibility is paramagnetic andhas an anomaly around 10 K in agreement with the ESR result.The chain axis optical reflectance spectra showclear optical gap in the mid-infrared region.An attempt is undertaken to analyzethe optical spectrumby means of the one-dimensional dimerized Hubbard model,which suggests that the on-site Coulomb repulsion,U, is small and the spin polarization islocated at the marginal paramagnetic boundary.These results indicate that this compound is not a band-insulatorbut the Mott insulator with a small spin gap.
Anisotropic Heisenberg form of RKKY interaction in the one-dimensional spin-polarized electron gas
NASA Astrophysics Data System (ADS)
Valizadeh, M. M.
2016-09-01
We study the indirect exchange interaction between two localized magnetic moments, known as Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, in a one-dimensional (1D) spin-polarized electron gas. We find explicit expressions for each term of this interaction, study their oscillatory behaviors as a function of the distance between two magnetic moments, R, and compare them with the known results for RKKY interaction in the case of 1D standard electron gas. We show this interaction can be written in an anisotropic Heisenberg form, E(R) = λ2χ xx(S1xS2x + S1yS2y) + λ2χ zzS1zS2z, coming from broken time-reversal symmetry of the host material.
Artificial topological models based on a one-dimensional spin-dependent optical lattice
NASA Astrophysics Data System (ADS)
Zheng, Zhen; Pu, Han; Zou, Xubo; Guo, Guangcan
2017-01-01
Topological matter is a popular topic in both condensed matter and cold-atom research. In the past decades, a variety of models have been identified with fascinating topological features. Some, but not all, of the models can be found in materials. As a fully controllable system, cold atoms trapped in optical lattices provide an ideal platform to simulate and realize these topological models. Here we present a proposal for synthesizing topological models in cold atoms based on a one-dimensional spin-dependent optical lattice potential. In our system, features such as staggered tunneling, staggered Zeeman field, nearest-neighbor interaction, beyond-near-neighbor tunneling, etc. can be readily realized. They underlie the emergence of various topological phases. Our proposal can be realized with current technology and hence has potential applications in quantum simulation of topological matter.
Formation of one-dimensional molecular chains on a solid surface: Pyrazine/Si(001)
Shimomura, M.; Ichikawa, D.; Fukuda, Y.; Abukawa, T.; Aoyama, T.; Kono, S.
2005-07-15
We have studied the chemisorption of pyrazine on Si(001)-2x1 at room temperature using scanning tunneling microscopy (STM), photoelectron diffraction (PED), and the density functional theory (DFT). In STM, protrusions ascribed to the pyrazine adsorbate were observed between the Si dimer rows and arrange themselves one-dimensionally (1D) along the dimer bond direction. Multiple scattering analysis of N 1s and C 1s PED patterns showed that a double-dimer bridging (DDB) configuration, in which pyrazine molecule forms bridging between the dimer rows with two Si-N bonds, is formed. DFT cluster calculations showed, however, that N-end-on configuration is more stable than the DDB configuration for a single molecule adsorption. The stability for the DDB configuration as a 1D chain is discussed on the basis of 'polymerization' of the adsorbates through dangling bonds at the distal points of the 1D chain.
Laser synthesis and stability of one-dimensional polyynic carbon chains in liquid media
NASA Astrophysics Data System (ADS)
Arutyunyan, Natalia R.; Fedotov, Pavel V.; Kononenko, Vitaly V.
2016-03-01
The results on femtosecond laser formation of polyynic linear carbon chains (LCCs) are reported. To reduce the oxidation and degradation of carbon chains, the synthesis of LCCs was performed in liquid media. The flakes of graphite were suspended in water or in hexane and ultrasonicated to obtain a suspension of micron-size graphite particles. This suspension was irradiated by pulses of Ti:sapphire laser. The spectral lines at 189, 199, 215, 225, 262, 276, 284, 299, 323, 342, and 368 nm in the optical absorption spectrum of the irradiated graphite suspension were clearly distinguished. They were attributed to the absorption of polyynic carbon chains CnH2, where n=2 to 20. The stability of the synthesized one-dimensional carbon chains suspended in water and hexane was defined based on the intensity of the optical absorption bands. Its half-life time was estimated to be 20 h at room temperature for water, and 7 and 25 days for hexane at 60°C and 5°C, respectively.
New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure
Xiong, Kecai; Liu, Wei; Teat, Simon J.; An, Litao; Wang, Hao; Emge, Thomas J.; Li, Jing
2015-10-15
Two new hybrid lead halides (H{sub 2}BDA)[PbI{sub 4}] (1) (H{sub 2}BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI{sub 3}] (2) (HNPEIM=N-phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively. - Graphical abstract: Two new hybrid lead halides built on one-dimensional edge-sharing double chains and two-dimensional corner-sharing perovskite layers are synthesized and their structural and electronic properties are analyzed. - Highlights: • Two new hybrid lead iodides are designed, synthesized, and characterized. • They are closely related to, but different from, perovskite structures. • The electronic properties of both compounds are analyzed by DFT calculations.
Single-photon transport through an atomic chain coupled to a one-dimensional nanophotonic waveguide
NASA Astrophysics Data System (ADS)
Liao, Zeyang; Zeng, Xiaodong; Zhu, Shi-Yao; Zubairy, M. Suhail
2015-08-01
We study the dynamics of a single-photon pulse traveling through a linear atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide. We derive a time-dependent dynamical theory for this collective many-body system which allows us to study the real time evolution of the photon transport and the atomic excitations. Our analytical result is consistent with previous numerical calculations when there is only one atom. For an atomic chain, the collective interaction between the atoms mediated by the waveguide mode can significantly change the dynamics of the system. The reflectivity of a photon can be tuned by changing the ratio of coupling strength and the photon linewidth or by changing the number of atoms in the chain. The reflectivity of a single-photon pulse with finite bandwidth can even approach 100 % . The spectrum of the reflected and transmitted photon can also be significantly different from the single-atom case. Many interesting physical phenomena can occur in this system such as the photonic band-gap effects, quantum entanglement generation, Fano-like interference, and superradiant effects. For engineering, this system may serve as a single-photon frequency filter, single-photon modulation, and may find important applications in quantum information.
A New One-dimensional Quantum Material - Ta2Pd3Se8 Atomic Chain
NASA Astrophysics Data System (ADS)
Liu, Xue; Liu, Jinyu; Hu, Jin; Yue, Chunlei; Mao, Zhiqiang; Wei, Jiang; Antipina, Liubov; Sorokin, Pavel; Sanchez, Ana
Since the discovery of carbon nanotube, there has been a persistent effort to search for other one dimensional (1D) quantum systems. However, only a few examples have been found. We report a new 1D example - semiconducting Ta2Pd3Se8. We demonstrate that the Ta2Pd3Se8 nanowire as thin as 1.3nm can be easily obtained by applying simple mechanical exfoliation from its bulk counterpart. High resolution TEM shows an intrinsic 1D chain-like crystalline morphology on these nano wires, indicating weak bonding between these atomic chains. Theoretical calculation shows a direct bandgap structure, which evolves from 0.53eV in the bulk to 1.04eV in single atomic chain. The field effect transistor based on Ta2Pd3Se8 nanowire achieved a promising performance with 104On/Off ratio and 80 cm2V-1s-1 mobility. Low temperature transport study reflects two different mechanisms, variable range hopping and thermal activation, which dominate the transport properties at different temperature regimes. Ta2Pd3Se8 nanowire provides an intrinsic 1D material system for the study low dimensional condensed matter physics.
Unexpected Huge Dimerization Ratio in One-Dimensional Carbon Atomic Chains.
Lin, Yung-Chang; Morishita, Shigeyuki; Koshino, Masanori; Yeh, Chao-Hui; Teng, Po-Yuan; Chiu, Po-Wen; Sawada, Hidetaka; Suenaga, Kazutomo
2017-01-11
Peierls theory predicted atomic distortion in one-dimensional (1D) crystal due to its intrinsic instability in 1930. Free-standing carbon atomic chains created in situ in transmission electron microscope (TEM)1-3 are an ideal example to experimentally observe the dimerization behavior of carbon atomic chain within a finite length. We report here a surprisingly huge distortion found in the free-standing carbon atomic chains at 773 K, which is 10 times larger than the value expected in the system. Such an abnormally distorted phase only dominates at the elevated temperatures, while two distinct phases, distorted and undistorted, coexist at lower or ambient temperatures. Atom-by-atom spectroscopy indeed shows considerable variations in the carbon 1s spectra at each atomic site but commonly observes a slightly downshifted π* peak, which proves its sp(1) bonding feature. These results suggest that the simple model, relaxed and straight, is not fully adequate to describe the realistic 1D structure, which is extremely sensitive to perturbations such as external force or boundary conditions.
NASA Astrophysics Data System (ADS)
Chen, Yuan; Xiang, Ying; Song, Chuang-Chuang
2010-10-01
In this paper, we apply the two-time Green's function method, and provide a simple way to study the magnetic properties of one-dimensional spin-(S,s) Heisenberg ferromagnets. The magnetic susceptibility and correlation functions are obtained by using the Tyablikov decoupling approximation. Our results show that the magnetic susceptibility and correlation length are a monotonically decreasing function of temperature regardless of the mixed spins. It is found that in the case of S=s, our results of one-dimensional mixed-spin model is reduced to be those of the isotropic ferromagnetic Heisenberg chain in the whole temperature region. Our results for the susceptibility are in agreement with those obtained by other theoretical approaches.
Li, Yan; Zhao, Pu; Zhang, Shan; Li, Rui; Zhang, Yi-Quan; Yang, En-Cui; Zhao, Xiao-Jun
2017-08-21
A novel water and hydroxyl-extended one-dimensional dysprosium(III) chain was hydrothermally obtained, which exhibits a relatively high spin-reversal energy barrier of 88.7 K and intrachain ferromagnetic interaction with the coupling constant Jexch = 3.04 cm(-1) calculated by fitting magnetic susceptibilities using POLY_ANISO program based on ab initio calculations. To deeply understand the respective role of the single-ion anisotropy and intrachain exchange on the effective energy barrier, three crystallographically isostructural analogues containing isotropic Gd(III)-, diamagnetic Y(III)-, as well as Y(III)-doped Dy0.05Y0.95 were prepared and characterized structurally and magnetically. Due to the absence of significant intrachain exchange interaction, the effective energy barrier of the Dy0.05Y0.95 decreased by 9.9 K as compared with that of parent dysprosium(III) chain. Thus, it can be concluded that the intrachain ferromagnetic coupling and the magnetic anisotropy of the Dy(III) ion synergistically enhance the effective energy barrier of the dysprosium(III) chain, in which the single-ion anisotropy becomes more predominant.
Berman, D. H.; Khodas, M.; Flatté, M. E.
2014-10-15
We study the spin transport in a quasi-one-dimensional channel defined in a two-dimensional electron gas. The combined action of geometrical confinement and the spin precession is analyzed. We demonstrate that for certain orientations of the in-plane magnetic field and for specific range of its magnitude the spin polarization exhibits a strong decrease referred to as ballistic spin resonance (BSR). The phenomenon is due to the commensuration of the Zeeman and inter-subband energy splitting. We show that the BSR requires a finite spin-orbit (SO) interaction although the condition for the BSR onset is independent on SO coupling.
U(1) chiral symmetry in a one-dimensional interacting electron system with spin
NASA Astrophysics Data System (ADS)
Lee, Taejin
2016-11-01
We study a spin-dependent Tomonaga-Luttinger model in one dimension, which describes electron transport through a single barrier. Using the Fermi-Bose equivalence in one dimension, we map the model onto a massless Thirring model with a boundary interaction. A field theoretical perturbation theory for the model has been developed, and the chiral symmetry is found to play an important role. The classical bulk action possesses a global U A (1)4 chiral symmetry because the fermion fields are massless. This global chiral symmetry is broken by the boundary interaction, and the bosonic degrees of freedom, corresponding to a chiral phase transformation, become dynamical. They acquire an additional kinetic action from the fermion path-integral measure and govern the critical behaviors of the physical operators. On the critical line where the boundary interaction becomes marginal, they decouple from the fermi fields. Consequently, the action reduces to the free-field action, which contains only a fermion bilinear boundary mass term as an interaction term. By using a renormalization group analysis, we obtain a new critical line, which differs from the previously known critical lines in the literature. The result of this work implies that the phase diagram of the one-dimensional electron system may have a richer structure than previously thought.
Spin-Orbit Coupled s-Wave Superconductor in One-Dimensional Optical Lattice
NASA Astrophysics Data System (ADS)
Yang, Li-Jun; Lang, Li-Jun; Lü, Rong; Hu, Hai-Ping
2015-04-01
We study the topological properties of spin-orbit coupled s-wave superconductor in one-dimensional optical lattice. Compared to its corresponding continuum model, the single particle spectrum is modified by the optical lattice and the topological phase which is characterized by the Majorana edge modes can survive in two regions of the single-particle spectrum. With the help of the self-consistent Bogoliubov-de Gennes calculation in the harmonic trap, we find that the existence of an upper critical magnetic field removes the topological superconductor phase to the trap wings. We also study the effects of nonmagnetic and magnetic impurity on the topological properties, and find the universal behavior of the mid-gap state induced by impurity in the topological superconductor phase in strong scattering limit. Supported by National Program for Basic Research of MOST (973 grant), and by National Natural Science Foundation of China under Grant Nos. 11121063, 11174360, 11374354, 11274195, 2011CB606405 and 2013CB922000
A one-dimensional chain structure based on unusual tetranuclear manganese(II) clusters.
Che, Guang Bo; Wang, Jian; Liu, Chun Bo; Li, Xiu Ying; Liu, Bo
2008-11-01
The title coordination polymer, poly[bis(mu(4)-biphenyl-2,2'-dicarboxylato)(dipyrido[3,2-a:2',3'-c]phenazine)manganese(II)], [Mn(2)(C(14)H(8)O(4))(2)(C(18)H(10)N(4))](n), was obtained through the reaction of MnCl(2).4H(2)O, biphenyl-2,2'-dicarboxylic acid (H(2)dpdc) and dipyrido[3,2-a:2',3'-c]phenazine (L) under hydrothermal conditions. The asymmetric unit contains two crystallographically unique Mn(II) ions, one unique L ligand and two unique dpdc ligands. One Mn ion is six-coordinated by four O atoms from three different dpdc ligands and two N atoms from one L ligand, adopting a distorted octahedral coordination geometry. The distortions from ideal octahedral geometry are largely due to the presence of chelating ligands and the resulting acute N-Mn-N and O-Mn-O angles. The second Mn ion is coordinated in a distorted trigonal bipyramidal fashion by five O atoms from four distinct dpdc ligands. Four Mn(II) ions are bridged by the carboxylate groups of the dpdc ligands to form an unusual tetranuclear Mn(II) cluster. Clusters are further connected by the aromatic backbone of the dicarboxylate ligands, forming a one-dimensional chain structure along the b axis. The title compound is the first example of a chain structure based on a tetranuclear Mn(II) cluster.
NASA Astrophysics Data System (ADS)
Poborchii, Vladimir V.; Lindner, Gottlieb-Georg; Sato, Mitsuo
2002-02-01
Cancrinite crystals possessing parallel nanochannels are attractive for incorporation of guest materials and preparation of one-dimensional structures. In this work, we study variety of cancrinite crystals synthesized with Se inside their channels. Single crystal x-ray diffraction, polarized Raman, optical absorption, and luminescence spectra are investigated. It is shown that Se is stabilized in the form of Se22- and Se2- dimers located in the center of the channel and oriented along the channel. Different absolute and relative concentrations of Se22- and Se2- are obtained for different samples. The Se22- dimers at high concentration show tendency to organize linear chains. At low temperatures, quite strong interdimer bonding for both Se22- and Se2- is observed. Another important low-temperature effect is appearance of additional Raman bands, which are attributed to the vibrations of linear Se22- chains distorted by the incommensurate potential of cancrinite. Strong near-infrared polarized luminescence is observed for all samples. Photoionization of dimers is shown to be important step in the mechanism of the luminescence.
Spin glass and semiconducting behavior in one-dimensional BaFe2-dSe3 (d~2) crystals
Saparov, Bayrammurad I; Calder, Stuart A; Sipos, Balazs; Cao, Huibo; Chi, Songxue; Singh, David J; Christianson, Andrew D; Lumsden, Mark D; Sefat, A. S.
2011-01-01
We investigate the physical properties and electronic structure of BaFe{sub 1.79(2)}Se{sub 3} crystals, which were grown out of tellurium flux. The crystal structure of the compound, an iron-deficient derivative of the ThCr{sub 2}Si{sub 2}-type, is built upon edge-shared FeSe{sub 4} tetrahedra fused into double chains. The semiconducting BaFe{sub 1.79(2)}Se{sub 3} ({rho}{sub 295K} = 0.18 {Omega} {center_dot} cm and E{sub g} = 0.30 eV) does not order magnetically; however, there is evidence for short-range magnetic correlations of spin glass type (T{sub f} {approx} 50 K) in magnetization, heat capacity, and neutron diffraction results. A one-third substitution of selenium with sulfur leads to a slightly higher electrical conductivity ({rho}{sub 295K } = 0.11 {Omega} {center_dot} cm and E{sub g} = 0.22 eV) and a lower spin glass freezing temperature (T{sub f} {approx} 15 K), corroborating with higher electrical conductivity reported for BaFe{sub 2}S{sub 3}. According to the electronic structure calculations, BaFe{sub 2}Se{sub 3} can be considered as a one-dimensional ladder structure with a weak interchain coupling.
NASA Astrophysics Data System (ADS)
Assaad, F. F.
2008-10-01
We use a recently developed extension of the weak-coupling diagrammatic determinantal quantum Monte Carlo method to investigate the spin, charge, and single-particle spectral functions of the one-dimensional quarter filled Holstein model with phonon frequency ω0=0.1t . As a function of the dimensionless electron-phonon coupling we observe a transition from a Luttinger to a Luther-Emery liquid with dominant 2kf charge fluctuations. Emphasis is placed on the temperature dependence of the single-particle spectral function. At high temperatures and in both phases it is well accounted for within a self-consistent Born approximation. In the low-temperature Luttinger liquid phase we observe features that compare favorably with a bosonization approach retaining only forward scattering. In the Luther-Emery phase, the spectral function at low temperatures shows a quasiparticle gap that matches half the spin gap, whereas at temperatures above which this quasiparticle gap closes characteristic features of the Luttinger liquid model are apparent. Our results are based on lattice simulations on chains up to L=20 for two-particle properties and on cluster dynamical mean-field theory calculations with clusters up to 12 sites for the single-particle spectral function.
Gate-Voltage Response of a One-Dimensional Ballistic Spin Valve without Spin-Orbit Interaction
NASA Astrophysics Data System (ADS)
Misiorny, Maciej; Meyer, Carola
2017-02-01
We show that the engineering of tunnel barriers forming at the interfaces of a one-dimensional spin valve provides a viable path to a strong gate-voltage tunability of the magnetoresistance effect. Specifically, we investigate theoretically a carbon nanotube (CNT) spin valve in terms of the influence of the CNT-contact interface on the performance of the device. The focus is on the strength and the spin selectivity of the tunnel barriers that are modeled as Dirac-δ potentials. The scattering matrix approach is used to derive the transmission coefficient that yields the tunneling magnetoresistance (TMR). We find a strong nontrivial gate-voltage response of the TMR in the absence of spin-orbit coupling when the energy of the incident electrons matches the potential energy of the barrier. Analytic expressions for the TMR in various limiting cases are derived. These expressions are used to explain previous experimental results, and also to predict prospective ways for device optimization with respect to the size and tunability of the TMR effect in the ballistic transport regime by means of engineering the tunnel barriers at the CNT-contact interfaces.
NMR study on the quasi one-dimensional quantum spin magnet with ladder structure
NASA Astrophysics Data System (ADS)
Kobori, Shohei; Matsui, Kazuki; Kuwahara, Hideki; Goto, Takayuki; Zhang, Xiao; Nakano, Yuki; Nishihara, Sadafumi; Inoue, Katsuya; Sasaki, Takahiko
2016-12-01
The two-legged spin ladder Cu(CO3)0.5(ClO4)(H2O)0.5(NH3)2.5 consists of a rung formed by two Cu(II)'s and of a spacing molecule CO3^{2-} between each two rungs. The non-centrosymmetric shape of CO3^{2-} molecule brings a slight bond alternation along the leg, and hence the system can be considered as an alternating spin chain, which is confirmed so far by the temperature dependence of magnetic susceptibility. In order to investigate its spin state at low temperatures, we have performed experiments of 1H-NMR, magnetization and specific heat under wide range of magnetic field, and have found the critical diverging of longitudinal relaxation rate 1/ T 1, the spectral broadening and the lambda-type anomaly in specific heat at T N≃ 3.4 K, indicating the existence of long range magnetic order. In paramagnetic state well above T N, 1/ T 1 showed a power-law temperature dependence, suggesting the realization of Tomonaga Luttinger liquid state.
Vector chiral spin liquid phase in quasi-one-dimensional incommensurate helimagnets
Cinti, Fabio; Cuccoli, Alessandro; Rettori, Angelo
2011-05-01
Making use of detailed classical Monte Carlo simulations, we study the critical properties of a two-dimensional planar spin model on a square lattice composed by weakly interacting helimagnetic chains. We find a large temperature window where the vector chirality order parameter, <{kappa}{sub jk}> = , the key quantity in multiferroic systems, takes nonzero value in the absence of long-range order or quasi-long-range order. The phase diagram we obtain for different strengths of the interchain coupling clearly shows that the weakness of the interchain interaction plays an essential role in order to observe the vector chiral spin liquid phase in a temperature range of up to now unattained width ({approx_equal}7%, to be compared with {approx_equal}1% or less previously reported for fully frustrated models, the only well-investigated systems unambiguously displaying spin-chirality decoupling). The relevance of our results for three-dimensional models is also discussed.
NASA Astrophysics Data System (ADS)
Greenberg, Ya. S.; Shtygashev, A. A.
2015-12-01
We investigate the propagation of microwave photons in a one-dimensional open waveguide interacting with a number of artificial atoms (qubits). Within the formalism of projection operators and a non-Hermitian Hamiltonian approach we develop a one-photon approximation scheme for the calculation of the transmission and reflection factors of the microwave signal in a waveguide which contains an arbitrary number N of noninteracting qubits. We considered in detail the resonances and photon-mediated entanglement for two and three qubits in a chain. We showed that in the non-Markovian case the resonance widths, which define the decay rates of the entangled state, can be much smaller than the decay width of an individual qubit. It is also shown that for identical qubits in the long-wavelength limit a coherent superradiant state is formed with the width being equal to the sum of the widths of spontaneous transitions of N individual qubits. The results obtained in the paper are of general nature and can be applied to any type of qubits. The specific properties of the qubit are only encoded in the two parameters: the qubit energy Ω and the rate of spontaneous emission Γ .
Electronic transport properties in random one-dimensional chains containing mesoscopic-ring defects
NASA Astrophysics Data System (ADS)
Huang, X.
1999-11-01
We study the electronic transport properties in one-dimensional systems with two kinds of mesoscopic ring defects: squarelike mesoscopic ring (SMR) defects and siamese-twins-like mescoscopic ring (STMR) defects. By using the transfer-matrix method, the resonant energies (where the transmission coefficient T=1) are derived successfully for both system. For the one SMR defect system, two resonant energies are found as a function of the magnetic flux Φ threading the ring defect, while for the latter case, two magnetic-flux-dependent and one magnetic-flux-independent resonant energies are predicted in the system, furthermore, if Φ takes some specific values, one of the Φ-dependent resonant energies may be the same as the Φ-independent resonant energy. The word ``resonant'' is used to describe this situation. When a finite concentration of SMR or STMR defects are randomly embedded in a perfect chain, the numerical results confirm all the analytical predictions. Finally, for the ``resonant'' case, we show numerically a rather wide perfect transmission region which is almost ten times as wide as that of the ``unresonant'' case.
Bound states of the spin-orbit coupled ultracold atom in a one-dimensional short-range potential
Jursenas, Rytis; Ruseckas, Julius
2013-05-15
We solve the bound state problem for the Hamiltonian with the spin-orbit and the Raman coupling included. The Hamiltonian is perturbed by a one-dimensional short-range potential V which describes the impurity scattering. In addition to the bound states obtained by considering weak solutions through the Fourier transform or by solving the eigenvalue equation on a suitable domain directly, it is shown that ordinary point-interaction representations of V lead to spin-orbit induced extra states.
NASA Astrophysics Data System (ADS)
Xianlong, Gao
2008-08-01
Using the Bethe-ansatz density-functional theory, we study a one-dimensional Hubbard model of confined attractively interacting fermions in the presence of a uniformly distributed disorder. The strongly correlated Luther-Emery nature of the attractive one-dimensional Hubbard model is fully taken into account as the reference system in the density-functional theory. The effects of the disorder are investigated on the atomic density waves in the weak-to-intermediate attractive interaction and on the spin-singlet dimers of doubly occupied sites in the strongly attractive regime. It is found that atomic density waves are sensitive to the disorder and the spin-singlet dimers of doubly occupied sites are quite unstable against the disorder. We also show that a very weak disorder could smear the singularities in the stiffness, thus, suppresses the spin-singlet pairs.
Competing interactions in artificial spin chains
NASA Astrophysics Data System (ADS)
Nguyen, V.-D.; Perrin, Y.; Le Denmat, S.; Canals, B.; Rougemaille, N.
2017-07-01
The low-energy magnetic configurations of artificial, frustrated classical spin chains are investigated using magnetic force microscopy and micromagnetic simulations. Contrary to most studies on two-dimensional artificial spin systems in which frustration arises from the lattice geometry, here magnetic frustration originates from competing interactions between neighboring spins. By tuning continuously the strength and sign of these interactions, we show that different magnetic phases can be stabilized. Comparison between our experimental findings and predictions from the one-dimensional anisotropic next-nearest-neighbor Ising model reveals that artificial frustrated spin chains have a richer phase diagram than initially expected. In addition to the observation of several magnetic orders and the potential extension of this work to highly degenerated artificial spin chains, our results suggest that the micromagnetic nature of the individual magnetic elements allows for the observation of metastable spin configurations.
Magnetic tetrastability in a spin chain
NASA Astrophysics Data System (ADS)
Pianet, Vivien; Urdampilleta, Matias; Colin, Thierry; Clérac, Rodolphe; Coulon, Claude
2016-08-01
Bistability in magnetism is extensively used, in particular for information storage. Here an alternative approach using tetrastable magnetic domains in one-dimensional (1D) spin systems is presented. Using numerical and analytical calculations, we show that a spin chain with a canting angle of π/4 possesses four energy-equivalent states. We discuss the static properties of this canted 1D system such as the profile and the energy of the domain walls as they govern the dynamics of the magnetization. The realization of this π/4 canted spin chain could enable the encoding of the information on four bits, which is a potential alternative toward the increase of storage density.
Transition between one-dimensional and zero-dimensional spin transport studied by Hanle precession
NASA Astrophysics Data System (ADS)
Wojtaszek, M.; Vera-Marun, I. J.; van Wees, B. J.
2014-06-01
The precession of electron spins in a perpendicular magnetic field, the so-called Hanle effect, provides an unique insight into spin properties of a nonmagnetic material. In practice, the spin signal is fitted to the analytic solution of the spin Bloch equation, which accounts for diffusion, relaxation, and precession effects on spin. The analytic formula, however, is derived for an infinite length of the 1D spin channel. This is usually not satisfied in the real devices. The finite size of the channel length ldev leads to confinement of spins and increase of spin accumulation. Moreover, reflection of spins from the channel ends leads to spin interference, altering the characteristic precession line shape. In this work we study the influence of finite ldev on the Hanle line shape and show when it can lead to a twofold discrepancy in the extracted spin coefficients. We propose the extension of the Hanle analytic formula to include the geometrical aspects of the real device and get an excellent agreement with a finite-element model of spin precession, where this geometry is explicitly set. We also demonstrate that in the limit of a channel length shorter than the spin relaxation length λs, the spin diffusion is negligible and a 0D spin transport description with the Lorentzian precession dependence applies. We provide a universal criterion for which transport description, 0D or 1D, to apply depending on the ratio ldev/λs and the corresponding accuracy of such a choice.
NASA Astrophysics Data System (ADS)
Okamoto, Kentaro; Tanaka, Toshiyuki; Fujita, Wataru; Awaga, Kunio; Inabe, Tamotsu
2007-08-01
We here examine the electrical and magnetic properties of the isostructural NT3•MCl4 ( NT=naphtho [2,1- d :6,5- d' ]bis([1,2,3] dithiazole and M=Ga and Fe). The crystal structure of NT3•MCl4 consists of one-dimensional π -stacking chains of NT with strong interchain interactions caused by electrostatic Sδ+•••Nδ- contacts. This structure includes four NT molecules with significant differences in molecular structure and charge, exhibiting a characteristic charge ordering, namely, three-dimensional alternation of charge-rich (or -intermediate) and -poor molecules. NT3•GaCl4 and NT3•FeCl4 are found to be semiconductors with σRT˜0.5Scm-1 and to exhibit a nonlinear electrical transport at room temperature with a very low threshold field of 80Vcm-1 for the negative differential resistance. This threshold field significantly increases with a decrease in temperature. The X -band electron paramagnetic resonance (EPR) spectra of NT3•GaCl4 consist of a single-line absorption ascribable to that of the NT+ cation. When the sample is exposed to a current at room temperature, this signal exhibits a drastic decrease in intensity with little change in linewidth. This is attributed to the inhomogeneous formation of EPR-silent conducting pathways for the nonlinear transport. The temperature dependence of the EPR spin susceptibility χs of NT3•GaCl4 suggests a transition toward a spin-gap state below 20K ; χs exhibits a Bonner-Fisher-type temperature dependence above 20K , but gradually collapses to zero below this temperature.
Basu, Banasri; Bandyopadhyay, Pratul; Majumdar, Priyadarshi
2011-03-15
We have studied quantum phase transition induced by a quench in different one-dimensional spin systems. Our analysis is based on the dynamical mechanism which envisages nonadiabaticity in the vicinity of the critical point. This causes spin fluctuation which leads to the random fluctuation of the Berry phase factor acquired by a spin state when the ground state of the system evolves in a closed path. The two-point correlation of this phase factor is associated with the probability of the formation of defects. In this framework, we have estimated the density of defects produced in several one-dimensional spin chains. At the critical region, the entanglement entropy of a block of L spins with the rest of the system is also estimated which is found to increase logarithmically with L. The dependence on the quench time puts a constraint on the block size L. It is also pointed out that the Lipkin-Meshkov-Glick model in point-splitting regularized form appears as a combination of the XXX model and Ising model with magnetic field in the negative z axis. This unveils the underlying conformal symmetry at criticality which is lost in the sharp point limit. Our analysis shows that the density of defects as well as the scaling behavior of the entanglement entropy follows a universal behavior in all these systems.
NASA Astrophysics Data System (ADS)
Badrtdinov, D. I.; Volkova, O. S.; Tsirlin, A. A.; Solovyev, I. V.; Vasiliev, A. N.; Mazurenko, V. V.
2016-08-01
We study electronic and magnetic properties of the quasi-one-dimensional spin-1/2 magnet Ba3Cu3Sc4O12 with a distinct orthogonal connectivity of CuO4 plaquettes. An effective low-energy model taking into account spin-orbit coupling was constructed by means of first-principles calculations. On this basis, a complete microscopic magnetic model of Ba3Cu3Sc4O12 , including symmetric and antisymmetric anisotropic exchange interactions, is derived. The anisotropic exchanges are obtained from a distinct first-principles numerical scheme combining, on one hand, the local density approximation taking into account spin-orbit coupling, and, on the other hand, a projection procedure along with the microscopic theory by Moriya [Phys. Rev. 120, 91 (1960), 10.1103/PhysRev.120.91]. The resulting tensors of the symmetric anisotropy favor collinear magnetic order along the structural chains with the leading ferromagnetic coupling J1≃-9.88 meV. The interchain interactions J8≃0.21 and J5≃0.093 meV are antiferromagnetic. Quantum Monte Carlo simulations demonstrate that the proposed model reproduces the experimental Neel temperature, magnetization, and magnetic susceptibility data. The modeling of neutron-diffraction data reveals an important role of the covalent Cu-O bonding in Ba3Cu3Sc4O12 .
Dynamical spin injection at a quasi-one-dimensional ferromagnet-graphene interface
Singh, S.; Ahmadi, A.; Mucciolo, E. R.; Barco, E. del; Cherian, C. T.; Özyilmaz, B.
2015-01-19
We present a study of dynamical spin injection from a three-dimensional ferromagnet into two-dimensional single-layer graphene. Comparative ferromagnetic resonance (FMR) studies of ferromagnet/graphene strips buried underneath the central line of a coplanar waveguide show that the FMR linewidth broadening is the largest when the graphene layer protrudes laterally away from the ferromagnetic strip, indicating that the spin current is injected into the graphene areas away from the area directly underneath the ferromagnet being excited. Our results confirm that the observed damping is indeed a signature of dynamical spin injection, wherein a pure spin current is pumped into the single-layer graphene from the precessing magnetization of the ferromagnet. The observed spin pumping efficiency is difficult to reconcile with the expected backflow of spins according to the standard spin pumping theory and the characteristics of graphene, and constitutes an enigma for spin pumping in two-dimensional structures.
NASA Astrophysics Data System (ADS)
Song, Chuang-Chuang; Chen, Yuan; Liu, Ming-Wei
2010-01-01
The magnetic properties of the one-dimensional spin-1 ferromagnetic Heisenberg model are investigated by Green's function method. The magnetic properties of the system are treated by the random phase approximation for the exchange interaction term, and the Anderson-Callen approximation for the single-ion anisotropy term. The critical temperature, magnetization, and susceptibility are found to be dependent of the anisotropies. Our results are in agreement with the other theoretical results.
Lee, J.Y.; Guan, X.W.
2011-01-01
We investigate the long distance asymptotics of various correlation functions for the one-dimensional spin-1/2 Fermi gas with attractive interactions using the dressed charge formalism. In the spin polarized phase, these correlation functions exhibit spatial oscillations with a power-law decay whereby their critical exponents are found through conformal field theory. We show that spatial oscillations of the leading terms in the pair correlation function and the spin correlation function solely depend on ΔkF and 2ΔkF, respectively. Here ΔkF=π(n↑−n↓) denotes the mismatch between the Fermi surfaces of spin-up and spin-down fermions. Such spatial modulations are characteristics of a Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state. Our key observation is that backscattering among the Fermi points of bound pairs and unpaired fermions results in a one-dimensional analog of the FFLO state and displays a microscopic origin of the FFLO nature. Furthermore, we show that the pair correlation function in momentum space has a peak at the point of mismatch between both Fermi surfaces k=ΔkF, which has recently been observed in numerous numerical studies. PMID:26594088
Zhai Hui; Zhou Fei
2005-07-01
We investigate the Zeeman-field-driven quantum phase transitions between singlet spin liquids and algebraically ordered O(2) nematic spin liquids of spin-one bosons in one-dimensional optical lattices. We find that the critical behavior is characterized by condensation of hardcore bosons instead of ideal magnons in high-dimensional lattices. Critical exponents are strongly renormalized by hardcore interactions and critical states are equivalent to the free Fermion model up to the Friedel oscillations. We also find that the algebraically ordered nematic spin liquids close to critical points are fully characterized by the Luttinger-liquid dynamics with Luttinger-liquid parameters magnetically tunable. The Bethe ansatz solution has been applied to determine the critical magnetization and nematic correlations.
Mapping of spin wave propagation in a one-dimensional magnonic crystal
Ordóñez-Romero, César L. Lazcano-Ortiz, Zorayda; Aguilar-Huerta, Melisa; Monsivais, Guillermo; Drozdovskii, Andrey; Kalinikos, Boris; Domínguez-Juárez, J. L.; Lopez-Maldonado, Guillermo; Qureshi, Naser; Kolokoltsev, Oleg
2016-07-28
The formation and evolution of spin wave band gaps in the transmission spectrum of a magnonic crystal have been studied. A time and space resolved magneto inductive probing system has been used to map the spin wave propagation and evolution in a geometrically structured yttrium iron garnet film. Experiments have been carried out using (1) a chemically etched magnonic crystal supporting the propagation of magnetostatic surface spin waves, (2) a short microwave pulsed excitation of the spin waves, and (3) direct spin wave detection using a movable magneto inductive probe connected to a synchronized fast oscilloscope. The results show that the periodic structure not only modifies the spectra of the transmitted spin waves but also influences the distribution of the spin wave energy inside the magnonic crystal as a function of the position and the transmitted frequency. These results comprise an experimental confirmation of Bloch′s theorem in a spin wave system and demonstrate good agreement with theoretical observations in analogue phononic and photonic systems. Theoretical prediction of the structured transmission spectra is achieved using a simple model based on microwave transmission lines theory. Here, a spin wave system illustrates in detail the evolution of a much more general physical concept: the band gap.
Mapping of spin wave propagation in a one-dimensional magnonic crystal
NASA Astrophysics Data System (ADS)
Ordóñez-Romero, César L.; Lazcano-Ortiz, Zorayda; Drozdovskii, Andrey; Kalinikos, Boris; Aguilar-Huerta, Melisa; Domínguez-Juárez, J. L.; Lopez-Maldonado, Guillermo; Qureshi, Naser; Kolokoltsev, Oleg; Monsivais, Guillermo
2016-07-01
The formation and evolution of spin wave band gaps in the transmission spectrum of a magnonic crystal have been studied. A time and space resolved magneto inductive probing system has been used to map the spin wave propagation and evolution in a geometrically structured yttrium iron garnet film. Experiments have been carried out using (1) a chemically etched magnonic crystal supporting the propagation of magnetostatic surface spin waves, (2) a short microwave pulsed excitation of the spin waves, and (3) direct spin wave detection using a movable magneto inductive probe connected to a synchronized fast oscilloscope. The results show that the periodic structure not only modifies the spectra of the transmitted spin waves but also influences the distribution of the spin wave energy inside the magnonic crystal as a function of the position and the transmitted frequency. These results comprise an experimental confirmation of Bloch's theorem in a spin wave system and demonstrate good agreement with theoretical observations in analogue phononic and photonic systems. Theoretical prediction of the structured transmission spectra is achieved using a simple model based on microwave transmission lines theory. Here, a spin wave system illustrates in detail the evolution of a much more general physical concept: the band gap.
Roubeau, Olivier; Castro, Miguel; Burriel, Ramón; Haasnoot, Jaap G; Reedijk, Jan
2011-03-31
The relevance of abrupt magnetic and optical transitions exhibiting bistability in spin-crossover solids has been pointed out for their potential applications in optical or memory devices. In this respect, triazole-based one-dimensional coordination polymers are widely recognized as one of the most interesting systems. The measure of the interaction among spin-crossover centers at the origin of such cooperative behavior is of paramount importance and has so far been realized through modeling of spin-crossover curves derived mostly from magnetic measurements. Here, a new series of triazole-based one-dimensional coordination polymers of formula [Fe(Rtrz)(3)](A)(2)·xH(2)O with R = methoxyethyl and A = monovalent anion has been prepared that show complete and abrupt spin-crossover phenomenon as shown by magnetic measurements. The spin-crossover transition in these and related compounds is studied by differential scanning calorimetry, and the thermodynamic excess enthalpies and entropies associated with the phenomenon are derived systematically. Then the cooperative character of the spin-crossover in these materials is quantified by use of two widely used models, so-called Slichter and Drickamer and domain models. The same procedure is applied to spin-crossover curves of similar compounds available in the literature and for which calorimetric studies have been reported. The experimental thermodynamic figures, in particular the excess enthalpies, are shown to be clearly correlated to the output parameters of both models, thus providing a direct, experimental, quantitative measure of the cooperative character of the spin-crossover phenomenon.
Spin-Orbit-Coupled Bose-Einstein Condensates in a One-Dimensional Optical Lattice
NASA Astrophysics Data System (ADS)
Hamner, C.; Zhang, Yongping; Khamehchi, M. A.; Davis, Matthew J.; Engels, P.
2015-02-01
We investigate a spin-orbit-coupled Bose-Einstein condensate loaded into a translating optical lattice. We experimentally demonstrate the lack of Galilean invariance in the spin-orbit-coupled system, which leads to anisotropic behavior of the condensate depending on the direction of translation of the lattice. The anisotropy is theoretically understood by an effective dispersion relation. We experimentally confirm this theoretical picture by probing the dynamical instability of the system.
Spin Chains with Dynamical Lattice Supersymmetry
NASA Astrophysics Data System (ADS)
Hagendorf, Christian
2013-02-01
Spin chains with exact supersymmetry on finite one-dimensional lattices are considered. The supercharges are nilpotent operators on the lattice of dynamical nature: they change the number of sites. A local criterion for the nilpotency on periodic lattices is formulated. Any of its solutions leads to a supersymmetric spin chain. It is shown that a class of special solutions at arbitrary spin gives the lattice equivalents of the {N}=(2,2) superconformal minimal models. The case of spin one is investigated in detail: in particular, it is shown that the Fateev-Zamolodchikov chain and its off-critical extension possess a lattice supersymmetry for all its coupling constants. Its supersymmetry singlets are thoroughly analysed, and a relation between their components and the weighted enumeration of alternating sign matrices is conjectured.
NASA Astrophysics Data System (ADS)
Leuzzi, L.; Parisi, G.; Ricci-Tersenghi, F.; Ruiz-Lorenzo, J. J.
2015-02-01
We revisited, by means of numerical simulations, the one-dimensional bond diluted Levy Ising spin glasses outside the limit of validity of mean-field theories. In these models the probability that two spins at distance r interact (via disordered interactions, Ji j=±1 ) decays as r-ρ. We have estimated, using finite size scaling techniques, the infinite volume correlation length and spin glass susceptibility for ρ =5 /3 and ρ =9 /5 . We have obtained strong evidence for divergences of the previous observables at a nonzero critical temperature. We discuss the behavior of the critical exponents, especially when approaching the value ρ =2 , corresponding to a critical threshold beyond which the model has no phase transition. Finally, we numerically study the model right at the threshold value ρ =2 .
Scaling of the largest dynamical barrier in the one-dimensional long-range Ising spin glass
NASA Astrophysics Data System (ADS)
Monthus, Cécile; Garel, Thomas
2014-01-01
The long-range one-dimensional Ising spin glass with random couplings decaying as J(r )∝r-σ presents a spin-glass phase Tc(σ)>0 for 0≤σ<1 (the limit σ =0 corresponds to the mean-field Sherrington-Kirkpatrick model). We use the eigenvalue method introduced in our previous work (C. Monthus and T. Garel, J. Stat. Mech. 2009, P12017) to measure the equilibrium time teq(N ) at temperature T =Tc(σ)/2 as a function of the number N of spins. We find the activated scaling lnteq(N )¯˜Nψ with the same barrier exponent ψ ≃0.33 in the whole region 0≤σ<1.
An interacting spin-flip model for one-dimensional proton conduction
NASA Astrophysics Data System (ADS)
Chou, Tom
2002-05-01
A discrete asymmetric exclusion process (ASEP) is developed to model proton conduction along one-dimensional water wires. Each lattice site represents a water molecule that can be in only one of three states; protonated, left-pointing and right-pointing. Only a right- (left-) pointing water can accept a proton from its left (). Results of asymptotic mean field analysis and Monte Carlo simulations for the three-species, open boundary exclusion model are presented and compared. The mean field results for the steady-state proton current suggest a number of regimes analogous to the low and maximal current phases found in the single-species ASEP (Derrida B 1998 Phys. Rep. 301 65-83). We find that the mean field results are accurate (compared with lattice Monte Carlo simulations) only in certain regimes. Refinements and extensions including more elaborate forces and pore defects are also discussed.
Magnetic properties of one-dimensional Au-Co chains on the copper(110) surface
NASA Astrophysics Data System (ADS)
Kolesnikov, S. V.; Tsysar, K. M.; Saletsky, A. M.
2015-08-01
Magnetic properties of cobalt atoms in Au-Co chains on the Cu(110) surface (such as the magnetic moment, magnetic anisotropy energy, and exchange energy) have been calculated in the framework of the density functional theory. It has been found, at zero temperature, an infinitely long Au-Co chain is in the ferromagnetic state. The magnetostatic and magnetodynamic properties of finite-length Au-Co chains at a nonzero temperature have been investigated within the Heisenberg model using the kinetic Monte Carlo method. The dependences of the Curie temperature and magnetization reversal time on the chain length have been obtained, as well as the dependences of the coercivity of the chain on the temperature, chain length, and magnetization reversal rate.
Purely one-dimensional bands with a giant spin-orbit splitting: Pb nanoribbons on Si(553) surface
Kopciuszyński, Marek; Krawiec, Mariusz; Zdyb, Ryszard; Jałochowski, Mieczysław
2017-01-01
We report on a giant Rashba type splitting of metallic bands observed in one-dimensional structures prepared on a vicinal silicon substrate. A single layer of Pb on Si(553) orders this vicinal surface making perfectly regular distribution of monatomic steps. Although there is only one layer of Pb, the system reveals very strong metallic and purely one-dimensional character, which manifests itself in multiple surface state bands crossing the Fermi level in the direction parallel to the step edges and a small band gap in the perpendicular direction. As shown by spin-polarized photoemission and density functional theory calculations these surface state bands are spin-polarized and completely decoupled from the rest of the system. The experimentally observed spin splitting of 0.6 eV at room temperature is the largest found to now in the silicon-based metallic nanostructures, which makes the considered system a promising candidate for application in spintronic devices. PMID:28383078
Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; ...
2016-06-06
The descloizite-type compound, SrMn(VO4)(OH), was synthesized as large single crystals (1-2mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P212121 (no. 19), Z = 4. The structure exhibits a one-dimensional feature, with [MnO4] chains propagating along the a-axis which are interconnected by VO4 tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant of J/kB = 9.97(3) K between nearestmore » Mn neighbors and a canted antiferromagnetic behavior below TN = 30 K. Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P21 with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. Lastly, the presence of the Dzyaloshinskii Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.« less
Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; McMillen, Colin D.; Cao, Huibo; Kolis, Joseph W.
2016-06-06
The descloizite-type compound, SrMn(VO_{4})(OH), was synthesized as large single crystals (1-2mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P2_{1}2_{1}2_{1} (no. 19), Z = 4. The structure exhibits a one-dimensional feature, with [MnO_{4}] chains propagating along the a-axis which are interconnected by VO_{4} tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant of J/k_{B} = 9.97(3) K between nearest Mn neighbors and a canted antiferromagnetic behavior below T_{N} = 30 K. Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P2_{1} with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. Lastly, the presence of the Dzyaloshinskii Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.
NASA Astrophysics Data System (ADS)
Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; McMillen, Colin D.; Cao, Huibo; Kolis, Joseph W.
2016-06-01
The descloizite-type compound, SrMn (V O4) (OH ) , was synthesized as large single crystals (1-2 mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P 212121 (no. 19), Z = 4 . The structure exhibits a one-dimensional feature, with [MnO4]∞ chains propagating along the a axis, which are interconnected by V O4 tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant of J /kB= 9.97 (3 ) K between nearest Mn neighbors and a canted antiferromagnetic behavior below TN= 30 K . Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P 21 with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. The presence of the Dzyaloshinskii-Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.
Sanjeewa, Liurukara D.; Garlea, Vasile O.; McGuire, Michael A.; McMillen, Colin D.; Cao, Huibo; Kolis, Joseph W.
2016-06-06
The descloizite-type compound, SrMn(VO_{4})(OH), was synthesized as large single crystals (1-2mm) using a high-temperature high-pressure hydrothermal technique. X-ray single crystal structure analysis reveals that the material crystallizes in the acentric orthorhombic space group of P2_{1}2_{1}2_{1} (no. 19), Z = 4. The structure exhibits a one-dimensional feature, with [MnO_{4}] chains propagating along the a-axis which are interconnected by VO_{4} tetrahedra. Raman and infrared spectra were obtained to identify the fundamental vanadate and hydroxide vibrational modes. Magnetization data reveal a broad maximum at approximately 80 K, arising from one-dimensional magnetic correlations with intrachain exchange constant of J/k_{B} = 9.97(3) K between nearest Mn neighbors and a canted antiferromagnetic behavior below T_{N} = 30 K. Single crystal neutron diffraction at 4 K yielded a magnetic structure solution in the lower symmetry of the magnetic space group P2_{1} with two unique chains displaying antiferromagnetically ordered Mn moments oriented nearly perpendicular to the chain axis. Lastly, the presence of the Dzyaloshinskii Moriya antisymmetric exchange interaction leads to a slight canting of the spins and gives rise to a weak ferromagnetic component along the chain direction.
Anomalous quantum heat transport in a one-dimensional harmonic chain with random couplings.
Yan, Yonghong; Zhao, Hui
2012-07-11
We investigate quantum heat transport in a one-dimensional harmonic system with random couplings. In the presence of randomness, phonon modes may normally be classified as ballistic, diffusive or localized. We show that these modes can roughly be characterized by the local nearest-neighbor level spacing distribution, similarly to their electronic counterparts. We also show that the thermal conductance G(th) through the system decays rapidly with the system size (G(th) ∼ L(-α)). The exponent α strongly depends on the system size and can change from α < 1 to α > 1 with increasing system size, indicating that the system undergoes a transition from a heat conductor to a heat insulator. This result could be useful in thermal control of low-dimensional systems.
Anti-resonance in a one-dimensional chain of driven coupled oscillators
NASA Astrophysics Data System (ADS)
Belbasi, Somayyeh; Ebrahim Foulaadvand, M.; Joe, Yong S.
2014-01-01
We investigate a driven system of N one-dimensional coupled oscillators with identical masses. The first mass is connected to a sinusoidal driving force of frequency ω. In the steady state, when all the masses perform simple harmonic motion, we analytically obtain the dependence of their amplitudes on ω and show that there are resonance and anti-resonance frequencies. At an anti-resonance frequency, the amplitude of one of the masses becomes exactly zero. The mass directly connected to the driving force has the largest number of anti-resonance frequencies, N - 1. The phase of each mass's motion is either 0 or π with respect to the driving force. The case where damping forces are present is also considered, and the amplitude dependence on driving frequency is analytically obtained. In the presence of damping, there is no anti-resonance.
S=2 quasi-one-dimensional spin waves in CrCl2
Stone, Matthew B; Ehlers, Georg; Granroth, Garrett E
2013-01-01
We examine the magnetic excitation spectrum in the S = 2 Heisenberg antiferromagnet CrCl2. Inelastic neutron scattering measurements on powder samples are able to determine the significant exchange interactions in this system. A large anisotropy gap is observed in the spectrum below the N eel temperature and the ratio of the two largest exchange constants is Jc=Jb = 4:51:6. However, no sign of a gapped quantum spin liquid excitation was found in the paramagnetic phase.
Numerical analysis of spin-orbit-coupled one-dimensional Fermi gas in a magnetic field
NASA Astrophysics Data System (ADS)
Chan, Y. H.
2015-06-01
Based on the density-matrix renormalization group and the infinite time-evolving block decimation methods we study the interacting spin-orbit-coupled 1D Fermi gas in a transverse magnetic field. We find that the system with an attractive interaction can have a polarized insulator phase, a superconducting (SC) phase, a Luther-Emery (LE) phase, and a band insulator phase as we vary the chemical potential and the strength of the magnetic field. Spin-orbit coupling (SOC) enhances the triplet pairing order at zero momentum in both the SC and the LE phase, which leads to an algebraically decaying correlation with the same exponent as that of the singlet pairing one. In contrast to the Fulde-Ferrell-Larkin-Ovchinnikov phase found in the spin imbalanced system without SOC, pairings at finite momentum in these two phases have larger exponents hence do not dictate the long-range behavior. We also test for the presence of Majorana fermions in this system. Unlike results from the mean-field study, we do not find positive evidence of Majorana fermions.
Ma, Fang; Bai, Dongsheng; Xu, Hongliang
2014-12-01
We present a theoretical investigation of the electric properties of two kinds of one-dimensional lithium bonded chains: (NC-Li)n and (NC-CC-Li)n (n = 1-8). The resulting (NC-Li)n and (NC-CC-Li)n were found to exhibit enhanced first hyperpolarizabilities (β 0) with increasing n, and a slight change in the absorption maximum wavelength λmax at the crucial transition. Comparing with (NC-Li)n, (NC-CC-Li)n exhibited particularly drastically enhanced β 0 values due to clearly enhanced coupled oscillators and double-degenerated charge transitions. β 0 is known to be the microscopic origin of the second-order non-linear optical (NLO) property, and λmax is an approximate measure of the transparency achievable, thus both are important indices of high-performance NLO molecules. Therefore, our investigations into one-dimensional lithium bond chains will be beneficial to understanding the relationship between β 0 and λmax, thus aiding the design of one-dimensional NLO materials with excellent transparence-efficiency.
Néel to spin-Peierls transition in a quasi-one-dimensional Heisenberg model coupled to bond phonons
NASA Astrophysics Data System (ADS)
Pillay, Jason Cornelius; Wierschem, Keola; Sengupta, Pinaki
2013-08-01
The zero and finite temperature spin-Peierls transitions in a quasi-one-dimensional spin-(1)/(2) Heisenberg model coupled to adiabatic bond phonons is investigated using the stochastic series expansion (SSE) quantum Monte Carlo (QMC) method. The quantum phase transition from a gapless Néel state to a spin-gapped Peierls state is studied in the parameter space spanned by spatial anisotropy, interchain coupling strength, and spin-lattice coupling strength. It is found that for any finite interchain coupling, the transition to a dimerized Peierls ground state only occurs when the spin-lattice coupling exceeds a finite, nonzero critical value. This is in contrast to the pure 1D model (zero interchain coupling), where adiabatic/classical phonons lead to a dimerized ground state for any nonzero spin-phonon interaction. The phase diagram in the parameter space shows that for a strong interchain coupling, the relation between the interchain coupling and the critical value of the spin-phonon interaction is linear whereas for weak interchain coupling, this behavior is found to have a natural logarithmlike relation. No region was found to have a long range magnetic order and dimerization occurring simultaneously. Instead, the Néel state order vanishes simultaneously with the setting in of the spin-Peierls state. For the thermal phase transition, a continuous heat capacity with a peak at the critical temperature Tc shows a second order phase transition. The variation of the equilibrium bond length distortion δeq with temperature showed a power law relation which decayed to zero as the temperature was increased to Tc, indicating a continuous transition from the dimerized phase to a paramagnetic phase with uniform bond length and zero antiferromagnetic susceptibility.
Imada, M. )
1993-07-01
The phase diagram of one-dimensional dimerized [ital t]-[ital J] model is investigated by exact-diagonalization, quantum tranfer-matrix, and quantum Monte Carlo methods. The spin gap persists near but away from half-filling as well as in a strongly dimerized region, while the charge can be described as a Tomonaga-Luttinger liquid in the entire region. The spin-gap region extends to the weak-dimerization region as well as to the Haldane-gap region. Critical exponents of various correlation functions are discussed. The pairing correlation shows remarkable enhancement and by far dominates over other correlations near half-filling. At quarter filling, charge-gap formation is observed.
Magnetic and Superfluid Transitions in the One-Dimensional Spin-1 Boson Hubbard Model
Batrouni, G. G.; Rousseau, V. G.; Scalettar, R. T.
2009-04-10
Recent progress in experiments on trapped ultracold atoms has made it possible to study the interplay between magnetism and superfluid-insulator transitions in the boson Hubbard model. We report on quantum Monte Carlo simulations of the spin-1 boson Hubbard model in the ground state. For antiferromagnetic interactions favoring singlets, we present exact numerical evidence that the superfluid-insulator transition is first (second) order for even (odd) Mott lobes. Inside even lobes, we search for nematic-to-singlet first order transitions. In the ferromagnetic case where transitions are all continuous, we map the phase diagram and show the superfluid to be ferromagnetic. We compare the quantum Monte Carlo phase diagram with a third order perturbation calculation.
Chiral spin liquids in arrays of spin chains
NASA Astrophysics Data System (ADS)
Gorohovsky, Gregory; Pereira, Rodrigo G.; Sela, Eran
2015-06-01
We describe a coupled-chain construction for chiral spin liquids in two-dimensional spin systems. Starting from a one-dimensional zigzag spin chain and imposing SU(2) symmetry in the framework of non-Abelian bosonization, we first show that our approach faithfully describes the low-energy physics of an exactly solvable model with a three-spin interaction. Generalizing the construction to the two-dimensional case, we obtain a theory that incorporates the universal properties of the chiral spin liquid predicted by Kalmeyer and Laughlin: charge-neutral edge states, gapped spin-1/2 bulk excitations, and ground-state degeneracy on the torus signaling the topological order of this quantum state. In addition, we show that the chiral spin liquid phase is more easily stabilized in frustrated lattices containing corner-sharing triangles, such as the extended kagome lattice, than in the triangular lattice. Our field-theoretical approach invites generalizations to more exotic chiral spin liquids and may be used to assess the existence of the chiral spin liquid as the ground state of specific lattice systems.
NASA Astrophysics Data System (ADS)
Zhou, Jing; Li, Yan; Zahl, Percy; Sutter, Peter; Stacchiola, Dario J.; White, Michael G.
2015-03-01
The morphology and electronic structure of vapor deposited 4,4'-biphenyldiisocyanide (BPDI) on a Au(111) surface were investigated using variable-temperature scanning tunneling microscopy. When deposited at room temperature, BPDI molecules form one-dimensional molecular chains similar to that recently observed for the structurally related 1,4-phenyl diisocyanide (PDI). Compared to PDI, the longer periodicity for the BPDI molecular chains is consistent with the addition of a second phenyl ring and supports a structural model in which the BPDI molecules lie parallel to the surface and interconnected by Au-adatoms. The molecular chains are mostly aligned along the [" separators=" 1 1 ¯ 0 ] direction of the Au(111) substrate, but exhibit frequent changes in angle that are consistent with directions between fcc and hcp three-fold hollow sites. Dispersion-corrected density functional theory calculations for one-dimensional chains of BPDI molecules bound end-to-end via their isocyanide groups to Au-adatoms reproduce the observed periodicity of the chains and show that this morphology is energetically favored over upright binding with one free —NC group. The spatially resolved conductance (dI/dV) map for BPDI on Au(111) exhibits a feature centered at -0.67 eV below the Fermi level which are delocalized along the chain with maxima at the Au-adatom and biphenyl positions. This occupied resonant feature is close to that previously observed for the PDI in both photoemission and conductance measurements and is attributed to an occupied interfacial state resulting from BPDI-Au interactions.
Zhou, Jing; Li, Yan; Zahl, Percy; ...
2015-03-14
The morphology and electronic structure of vapor deposited 4,4'-biphenyldiisocyanide (BPDI) on a Au(111) surface were investigated using variable-temperature scanning tunneling microscopy (STM). When deposited at room temperature, BPDI molecules form one-dimensional molecular chains similar to that recently observed for the structurally related 1,4-phenyl diisocyanide (PDI). Compared to PDI, the longer periodicity for the BPDI molecular chains is consistent with the addition of a second phenyl ring and supports a structural model in which the BPDI molecules lie parallel to the surface and interconnected by Au-adatoms. The molecular chains are mostly aligned along the [110] direction of the Au(111) substrate, butmore » exhibit frequent changes in angle that are consistent with directions between fcc and hcp three-fold hollow sites. Dispersion-corrected density functional theory calculations for one-dimensional chains of BPDI molecules bound end-to-end via their isocyanide groups to Au-adatoms reproduce the observed periodicity of the chains and show that this morphology is energetically favored over upright binding with one free –NC group. The spatially resolved conductance (dI/dV) map for BPDI on Au(111) exhibits a feature centered at -0.67 eV below the Fermi level which are delocalized along the chain with maxima at the Au-adatom and biphenyl positions. This occupied resonant feature is close to that previously observed for the PDI in both photoemission and conductance measurements and is attributed to an occupied interfacial state resulting from BPDI-Au interactions« less
Zhou, Jing; Li, Yan; Zahl, Percy; Sutter, Peter; Stacchiola, Dario J.; White, Michael G.
2015-03-14
The morphology and electronic structure of vapor deposited 4,4'-biphenyldiisocyanide (BPDI) on a Au(111) surface were investigated using variable-temperature scanning tunneling microscopy (STM). When deposited at room temperature, BPDI molecules form one-dimensional molecular chains similar to that recently observed for the structurally related 1,4-phenyl diisocyanide (PDI). Compared to PDI, the longer periodicity for the BPDI molecular chains is consistent with the addition of a second phenyl ring and supports a structural model in which the BPDI molecules lie parallel to the surface and interconnected by Au-adatoms. The molecular chains are mostly aligned along the [110] direction of the Au(111) substrate, but exhibit frequent changes in angle that are consistent with directions between fcc and hcp three-fold hollow sites. Dispersion-corrected density functional theory calculations for one-dimensional chains of BPDI molecules bound end-to-end via their isocyanide groups to Au-adatoms reproduce the observed periodicity of the chains and show that this morphology is energetically favored over upright binding with one free –NC group. The spatially resolved conductance (dI/dV) map for BPDI on Au(111) exhibits a feature centered at -0.67 eV below the Fermi level which are delocalized along the chain with maxima at the Au-adatom and biphenyl positions. This occupied resonant feature is close to that previously observed for the PDI in both photoemission and conductance measurements and is attributed to an occupied interfacial state resulting from BPDI-Au interactions
One-dimensional chain of quantum molecule motors as a mathematical physics model for muscle fibers
NASA Astrophysics Data System (ADS)
Si, Tie-Yan
2015-12-01
A quantum chain model of multiple molecule motors is proposed as a mathematical physics theory for the microscopic modeling of classical force-velocity relation and tension transients in muscle fibers. The proposed model was a quantum many-particle Hamiltonian to predict the force-velocity relation for the slow release of muscle fibers, which has not yet been empirically defined and was much more complicated than the hyperbolic relationships. Using the same Hamiltonian model, a mathematical force-velocity relationship was proposed to explain the tension observed when the muscle was stimulated with an alternative electric current. The discrepancy between input electric frequency and the muscle oscillation frequency could be explained physically by the Doppler effect in this quantum chain model. Further more, quantum physics phenomena were applied to explore the tension time course of cardiac muscle and insect flight muscle. Most of the experimental tension transient curves were found to correspond to the theoretical output of quantum two- and three-level models. Mathematical modeling electric stimulus as photons exciting a quantum three-level particle reproduced most of the tension transient curves of water bug Lethocerus maximus. Project supported by the Fundamental Research Foundation for the Central Universities of China.
NASA Astrophysics Data System (ADS)
Liu, Ming-Wei; Chen, Yuan; Song, Chuang-Chuang; Wu, You; Ding, Hai-Ling
2011-03-01
The effect of magnetic field h on the magnetic properties of the one-dimensional spin-1 ferromagnetic Heisenberg model is studied by the double-time Green's function method. The magnetization and susceptibility are obtained within the Callen approximation. The zero-field susceptibility is as a decreasing function of the temperature T. The magnetization m increases in the whole field region, but the susceptibility maximum χ(Tm) decreases. The position Tm of the susceptibility maximum is both solved analytically and fits well to be a power law Tm∼hγ at low fields and to be linear increasing at high fields. The height χ(Tm) decreases as a power law χ(Tm)∼h with h increasing. The exponents (γ,β) obtained in our results agree with the other theoretical results. Our results are roughly in agreement with the results obtained in the experiment of Ni(OH)(NO3)H2O.
Phase diagram of a one-dimensional spin-full Bose-Fermi mixture at large boson densities
NASA Astrophysics Data System (ADS)
Nocera, Alberto; Lutchyn, Roman M.; Feiguin, Adrian E.
2014-03-01
We determine the ground state phase diagram of a one dimensional Bose-Fermi Hubbard model with spin-full fermions using the Density Matrix Renormalization Group (DMRG) method. We focus on the regime with one fermion per site, and deep into the superfluid phase. We study the effects of the boson-fermion interaction on the fermionic pairing, as a function of the interaction strength, hopping, and bosonic density. We identify the regime in which fermionic superfluidity dominates, and a phase with coexisting CDW and bosonic superfluidity. At high boson densities we find a fermionic Wigner crystal coexisting with bosonic superfluidity. We analyze the structure of the Cooper pairs and the bosonic cloud that acts as the glue.
Yoshimura
2000-11-01
We study analytically the induction phenomenon in the Fermi-Pasta-Ulam beta oscillator chain under initial conditions consisting of single mode excitation. Our study is based on the analytical computation of the largest characteristic exponent of an approximate version of the variational equation. The main results can be summarized as follows: (1) the energy density epsilon scaling of the induction time T is given by T approximately epsilon(-1), and T becomes smaller for higher-frequency mode excitation; (2) there is a threshold energy density epsilon(c) such that the induction time diverges when epsilon
Quasi-one-dimensional K-O chain in PTCDA thin films: evidence from first-principles calculations.
Zazza, Costantino; Meloni, Simone; Palma, Amedeo; Knupfer, Martin; Fuentes, Gonzalo G; Car, Roberto
2007-01-26
Using density functional theory calculations we have found that K atoms in a PTCDA (3,4:9,10-perylenetetracarboxylic dianhydride) crystal form a quasi-one-dimensional (1D) K-O chain interacting with carboxylic oxygen of the terminal anhydride groups of PTCDA. The K-K distance in the chain (3.72 Angstrom) is commensurate to the periodicity of the organic semiconductor. We obtain that the K-O structure is stabilized by charge transfer from K to PTCDA molecules, forming prevalently ionic bonds: the electronic density of the chemistry induced gap states is essentially delocalized on the perylene core of PTCDA, while potassium appears spoiled of its charge. Band dispersion along the direction of molecular stack is evaluated to be 0.2 eV in pure PTCDA crystal and 0.5 eV in the K-doped system, confirming that the interaction occurs between different molecular planes.
Yoo-Kong, Sikarin; Liewrian, Watchara
2015-12-01
We report on a theoretical investigation concerning the polaronic effect on the transport properties of a charge carrier in a one-dimensional molecular chain. Our technique is based on the Feynman's path integral approach. Analytical expressions for the frequency-dependent mobility and effective mass of the carrier are obtained as functions of electron-phonon coupling. The result exhibits the crossover from a nearly free particle to a heavily trapped particle. We find that the mobility depends on temperature and decreases exponentially with increasing temperature at low temperature. It exhibits large polaronic-like behaviour in the case of weak electron-phonon coupling. These results agree with the phase transition (A.S. Mishchenko et al., Phys. Rev. Lett. 114, 146401 (2015)) of transport phenomena related to polaron motion in the molecular chain.
Spin rectification in thermally driven XXZ spin chain via the spin-Seebeck effect
NASA Astrophysics Data System (ADS)
Thingna, Juzar; Wang, Jian-Sheng
2013-11-01
We study the phenomenon of spin-current rectification in a one-dimensional XXZ spin chain in the presence of a thermal drive. In our model a pure spin current is generated by a temperature difference between two harmonic heat baths which in turn creates a spin voltage via the spin-Seebeck effect. Along with a local spin-current operator definition and the nonequilibrium modified Redfield solution we study the spin-rectification ratio as a function of system size and external magnetic field. Intriguing effects are observed at low temperatures such as oscillations with system size and high range of tunability with external magnetic field making magnetic insulators, which are well described by the XXZ model, ideal candidates to build spin devices based on rectification.
NASA Astrophysics Data System (ADS)
Bahari, Masoud; Hosseini, Mir Vahid
2016-09-01
We study theoretically the interplay effect of Zeeman field and modulated spin-orbit coupling on the topological properties of a one-dimensional dimerized lattice, known as Su-Schrieffer-Heeger model. We find that in the weak (strong) modulated spin-orbit coupling regime, trivial regions or nontrivial ones with two pairs of zero-energy states can be turned into nontrivial regions by applying a uniform (staggered) perpendicular Zeeman field through a topological phase transition. Furthermore, the resulting nontrivial phase hosting a pair of zero-energy boundary states can survive within a certain range of the perpendicular Zeeman field magnitude. Due to the effective time-reversal, particle-hole, chiral, and inversion symmetries, in the presence of either a uniform or a staggered perpendicular Zeeman field, the topological class of the system is BDI, which can be characterized by Z index. We also examine the robustness of the nontrivial phase by breaking the underlying symmetries, which results in that inversion symmetry plays an important role.
NASA Astrophysics Data System (ADS)
Qin, Ling; Chen, Peng-Yu; Zhao, Gao-Chao; Zuo, Wei-Juan; Li, Jin
2016-12-01
Two compounds with cation chains and monomers, [Co1/2(bpbenz)1/2]+·[Co1/2(oba)]- (1) and [Ni(DPT)(H2O)4]2+ [tpdc]2- (2) have been synthesized under hydrothermal condition (bpbenz = 1,4-bis(4-pyridyl)benzene, H2oba = 4,4‧-oxybis- (benzoate), DPT = 2,5-dipyridinethiophene, H2tpdc = biphenyldicarboxylic acid). In compound 1, the monomer [Co1/2(oba)]- anions stack in three orientations to generate a 1D pseudo channels encapsulation of cationic chains [Co1/2(bpbenz)1/2]+. When considering the H-bonding interaction between coordinated water O atoms of the [Co1/2(bpbenz) 1/2]+ cationic chain and uncoordinated carboxylate oxygen atoms of the [Co1/2(oba)]- anion, a binodal 3,6-coordinated 3D architecture is generated. Like 1, the one-dimensional cation chains [Ni(DPT)(H2O)4]2+ locate in pseudo-channels by [tpdc]2- monomers anions in compound 2. A 3D net is also generated considering the H-bonding interaction.
NASA Astrophysics Data System (ADS)
Roman-Taboada, Pedro; Naumis, Gerardo G.
2015-07-01
We report an exact map into one-dimensional effective chains of the tight-binding Hamiltonian for electrons in armchair and zigzag graphene nanoribbons with any uniaxial ripple. This mapping is used for studying the effect of uniaxial periodic ripples, taking into account the relative orientation changes between π orbitals. Such effects are important for short-wavelength ripples, while for long-wave ones, the system behaves nearly as strained graphene. The spectrum has a complex nature, akin to the Hofstadter butterfly with a rich localization behavior. Gaps at the Fermi level and dispersionless bands were observed, as well. The complex features of the spectrum arise as a consequence of the quasiperiodic or periodic nature of the effective one-dimensional system. Some features of these systems can be understood by considering weakly coupled dimers. The eigenenergies of such dimers are highly degenerate, and the net effect of the ripple can be seen as a perturbation potential that splits the energy spectrum. Several particular cases were analytically solved to understand this feature.
One-dimensional magnetic fluctuations in the spin-2 triangular lattice alpha-NaMnO2.
Stock, C; Chapon, L C; Adamopoulos, O; Lappas, A; Giot, M; Taylor, J W; Green, M A; Brown, C M; Radaelli, P G
2009-08-14
The S=2 anisotropic triangular lattice alpha-NaMnO2 is studied by neutron inelastic scattering. Antiferromagnetic order occurs at T< or =45 K with opening of a spin gap. The spectral weight of the magnetic dynamics above the gap (Delta approximately equal to 7.5 meV) has been analyzed by the single-mode approximation. Excellent agreement with the experiment is achieved when a dominant exchange interaction (|J|/k(B) approximately 73 K), along the monoclinic b axis and a sizable easy-axis magnetic anisotropy (|D|/k(B) approximately 3 K) are considered. Despite earlier suggestions for two-dimensional spin interactions, the dynamics illustrate strongly coupled antiferromagnetic S=2 chains and cancellation of the interchain exchange due to the lattice topology. alpha-NaMnO2 therefore represents a model system where the geometric frustration is resolved through the lowering of the dimensionality of the spin interactions.
NASA Astrophysics Data System (ADS)
Araki, Gako; Suzuki, Kazuaki; Nakayama, Hideyuki; Ishii, Kikujiro
1991-05-01
N-methylacetamide (NMA) crystal forms one-dimensional hydrogen-bond chains, which are similar to those in an acetanilide (ACN) crystal for which an unconventional vibrational band accompanying the amide-I band has been observed. Infrared spectra of NMA crystals show an additional band on the small-wave-number side of the amide-II band as the temperature is lowered. There is a close resemblance between this band and the band of ACN. It is likely that these bands appear by the same mechanism. The polaron model, which has been employed to explain the band of ACN, was found to be applicable also to the case of NMA, although the main vibrational mode is amide I in ACN and amide II in NMA.
NASA Astrophysics Data System (ADS)
Qian, Jing; Zhang, Lu; Zhai, Jingjing; Zhang, Weiping
2015-12-01
We theoretically investigate the dynamical phase diagram of a one-dimensional chain of laser-excited two-species Rydberg atoms. The existence of a variety of unique dynamical phases in the experimentally achievable parameter region is predicted under the mean-field approximation, and the change in those phases when the effect of the next-nearest-neighbor interaction is included is further discussed. In particular, we find that the com-petition of the strong Rydberg-Rydberg interactions and the optical excitation imbalance can lead to the presence of complex multiple chaotic phases, which are highly sensitive to the initial Rydberg-state population and the strength of the next-nearest-neighbor interactions.
Kavitha, L; Priya, R; Ayyappan, N; Gopi, D; Jayanthi, S
2016-01-01
The dynamics of protons in a one-dimensional hydrogen-bonded (HB) polypeptide chain (PC) is investigated theoretically. A new Hamiltonian is formulated with the inclusion of higher-order molecular interactions between peptide groups (PGs). The wave function of the excitation state of a single particle is replaced by a new wave function of a two-quanta quasi-coherent state. The dynamics is governed by a higher-order nonlinear Schrödinger equation and the energy transport is performed by the proton soliton. A nonlinear multiple-scale perturbation analysis has been performed and the evolution of soliton parameters such as velocity and amplitude is explored numerically. The proton soliton is thermally stable and very robust against these perturbations. The energy transport by the proton soliton is more appropriate to understand the mechanism of energy transfer in biological processes such as muscle contraction, DNA replication, and neuro-electric pulse transfer on biomembranes.
NASA Astrophysics Data System (ADS)
Han, Jae-Ho; Cho, Yong-Heum; Kim, Ki-Seok
2017-06-01
Resorting to a recently developed theoretical device called dimensional regularization for quantum criticality with a Fermi surface, we examine a metal-insulator quantum phase transition from a Landau's Fermi-liquid state to a U(1) spin-liquid phase with a spinon Fermi surface in two dimensions. Unfortunately, we fail to approach the spin-liquid Mott quantum critical point from the U(1) spin-liquid state within the dimensional regularization technique. Self-interactions between charge fluctuations called holons are not screened, which shows a run-away renormalization group flow, interpreted as holons remain gapped. This leads us to consider another fixed point, where the spinon Fermi surface can be destabilized across the Mott transition. Based on this conjecture, we reveal the nature of the spin-liquid Mott quantum critical point: Dimensional reduction to one dimension occurs for spin dynamics described by spinons. As a result, Landau damping for both spin and charge dynamics disappear in the vicinity of the Mott quantum critical point. When the flavor number of holons is over its critical value, an interacting fixed point appears to be identified with an inverted X Y universality class, controlled within the dimensional regularization technique. On the other hand, a fluctuation-driven first order metal-insulator transition results when it is below the critical number. We propose that the destabilization of a spinon Fermi surface and the emergence of one-dimensional spin dynamics near the spin-liquid Mott quantum critical point can be checked out by spin susceptibility with a 2 kF transfer momentum, where kF is a Fermi momentum in the U(1) spin-liquid state: The absence of Landau damping in U(1) gauge fluctuations gives rise to a divergent behavior at zero temperature while it vanishes in the presence of a spinon Fermi surface.
Direct measurement of the spin gap in a quasi-one-dimensional clinopyroxene: NaTiSi2O6
Silverstein, Harlyn J.; Smith, Alison E.; Mauws, Cole; ...
2014-10-13
True inorganic Spin-Peierls materials are extremely rare, but NaTiSi2O6 was at one time considered an ideal candidate due to it having well separated chains of edge-sharing TiO6 octahedra. At low temperatures, this material undergoes a phase transition from C2/c to Pmore » $$\\bar{1}$$ symmetry, where Ti3+-Ti3+ dimers begin to form within the chains. However, it was quickly realized with magnetic susceptibility that simple spin fluctuations do not progress to the point of enabling such a transition. Since then, considerable experimental and theoretical endeavours have been taken to find the true ground state of this system and explain how it manifests. Here, we employ the use of x-ray diffraction, neutron spectroscopy, and magnetic susceptibility to directly and simultaneously measure the symmetry loss, spin singlet-triplet gap, and phonon modes. Lastly, we observed a gap of 53(3) meV, fit to the magnetic susceptibility, and compared to previous theoretical models to unambiguously assign NaTiSi2O6 as having an orbital-assisted Peierls ground state.« less
Liang, Junjun; Zhou, Xiaofan; Chui, Pak Hong; Zhang, Kuang; Gu, Shi-jian; Gong, Ming; Chen, Gang; Jia, Suotang
2015-01-01
Understanding novel pairings in attractive degenerate Fermi gases is crucial for exploring rich superfluid physics. In this report, we reveal unconventional pairings induced by spin-orbit coupling (SOC) in a one-dimensional optical lattice, using a state-of-the-art density-matrix renormalization group method. When both bands are partially occupied, we find a strong competition between the interband Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) and intraband Bardeen-Cooper-Schrieffer (BCS) pairings. In particular, for the weak and moderate SOC strengths, these two pairings can coexist, giving rise to a new phase called the FFLO-BCS phase, which exhibits a unique three-peak structure in pairing momentum distribution. For the strong SOC strength, the intraband BCS pairing always dominates in the whole parameter regime, including the half filling. We figure out the whole phase diagrams as functions of filling factor, SOC strength, and Zeeman field. Our results are qualitatively different from recent mean-field predictions. Finally, we address that our predictions could be observed in a weaker trapped potential. PMID:26443006
One-dimensional and two-dimensional anilate-based magnets with inserted spin-crossover complexes.
Abhervé, Alexandre; Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; Verneret, Martin
2014-11-17
The syntheses, structures, and magnetic properties of a family of bimetallic anilate-based compounds with inserted spin-crossover cationic complexes are reported. The structures of 1-4 present a two-dimensional anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands with inserted [Fe(III)(sal2-trien)](+) (1), [Fe(III)(4-OH-sal2-trien)](+) (2), [Fe(III)(sal2-epe)](+) (3), or [Fe(III)(5-Cl-sal2-trien)](+) (4) complexes. The structure of 5 is formed by anionic [Mn(II)Cl2Cr(III)(Cl2An)3](3-) chains surrounded by [Fe(II)(tren(imid)3)](2+), Cl(-), and solvent molecules. The magnetic properties indicate that 1-4 undergo a long-range ferrimagnetic ordering at ca. 10 K. On the other hand, the inserted Fe(III) cations remain in the low-spin (in 4) or high-spin state (in 1, 2, and 3). In the case of 5, half of the inserted Fe(II) cations undergo a complete and gradual spin crossover from 280 to 90 K that coexists with a magnetic ordering below 2.5 K.
NASA Astrophysics Data System (ADS)
Lin, Hung-Jui; Liu, Yu-Chiao; Tseng, Yu-Jui; Wu, Jing-Yun
2016-10-01
Reactants slow diffusion of Ag(I) salts with 3,4‧-bis(pyridylmethyl)amine (3,4‧-bpma), an unsymmetric bis-pyridyl ligand equipped with a non-innocent amine backbone, afforded polymeric coordination adducts 1-5 having a general formula {[Ag(3,4‧-bpma)(solv)]X}n (solv = H2O, CH3OH, and none; X= CF3CO2-, BF4-, ClO4-, CF3SO3-, and SbF6-). Single-crystal X-ray diffraction (SCXRD) analyses reveal that colorless crystals of Ag(I) coordination polymers (CPs) 1-5 have very similar one-dimensional (1D) non-flat chain structures, which are preferentially depicted as a "zipper-like" rather than a ladder-like or a double-stranded chain topologies. The 3,4‧-bpma ligand in these Ag(I) CPs displays a μ3-bridging mode with a gauche-trans (1,4, and 5) and a trans-trans (2 and 3) conformations. Noteworthy, anions do not show strong influence on structural modulation of Ag(I) CPs in the solid state, but really affect CP conformations and packing fashions, indicative of a ligand-dominated assembly process for such a Ag(I)-3,4‧-bpma system. Thermal stabilities and solid-state photoluminescence properties of crystalline materials 1-5 were investigated.
NASA Astrophysics Data System (ADS)
Monthus, Cécile
2014-06-01
For the one-dimensional long-ranged Ising spin-glass with random couplings decaying with the distance $r$ as $J(r) \\sim r^{-\\sigma}$ and distributed with the L\\'evy symmetric stable distribution of index $1 <\\mu \\leq 2$ (including the usual Gaussian case $\\mu=2$), we consider the region $\\sigma>1/\\mu$ where the energy is extensive. We study two real space renormalization procedures at zero temperature, namely a simple box decimation that leads to explicit calculations, and a strong disorder decimation that can be studied numerically on large sizes. The droplet exponent governing the scaling of the renormalized couplings $J_L \\propto L^{\\theta_{\\mu}(\\sigma)}$ is found to be $\\theta_{\\mu}(\\sigma)=\\frac{2}{\\mu}-\\sigma$ whenever the long-ranged couplings are relevant $\\theta_{\\mu}(\\sigma)=\\frac{2}{\\mu}-\\sigma \\geq -1$. For the statistics of the ground state energy $E_L^{GS}$ over disordered samples, we obtain that the droplet exponent $\\theta_{\\mu}(\\sigma) $ governs the leading correction to extensivity of the averaged value $\\overline{E_L^{GS}} \\simeq L e_0 +L^{\\theta_{\\mu}(\\sigma)} e_1$. The characteristic scale of the fluctuations around this average is of order $L^{\\frac{1}{\\mu}}$, and the rescaled variable $u=(E_L^{GS}-\\overline{E_L^{GS}})/L^{\\frac{1}{\\mu}}$ is Gaussian distributed for $\\mu=2$, or displays the negative power-law tail in $1/(-u)^{1+\\mu}$ for $u \\to -\\infty$ in the L\\'evy case $1<\\mu<2$.
NASA Astrophysics Data System (ADS)
Demontis, Pierfranco; Stara, Giovanna; Suffritti, Giuseppe B.
2004-05-01
Nanosecond scale molecular dynamics simulations of the behavior of the one-dimensional water molecule chains adsorbed in the parallel nanochannels of bikitaite, a rare lithium containing zeolite, were performed at different temperatures and for the fully and partially hydrated material. New empirical potential functions have been developed for representing lithium-water interactions. The structure and the vibrational spectrum of bikitaite were in agreement both with experimental data and Car-Parrinello molecular dynamics results. Classical molecular dynamics simulations were extended to the nanosecond time scale in order to study the flip motion of water molecules around the hydrogen bonds connecting adjacent molecules in the chains, which has been observed by NMR experiments, and the dehydration mechanism at high temperature. Computed relaxation times of the flip motion follow the Arrhenius behavior found experimentally, but the activation energy of the simulated system is slightly underestimated. Based on the results of the simulations, it may be suggested that the dehydration proceeds by a defect-driven stepwise diffusion. The diffusive mechanism appears as a single-file motion: the molecules never pass one another, even at temperatures as high as about 1000 K, nor can they switch between different channels. However, the mean square displacement (MSD) of the molecules, computed with respect to the center of mass of the simulated system, shows an irregular trend from which the single-file diffusion cannot be clearly evidenced. If the MSDs are evaluated with respect to the center of mass of the molecules hosted in each channel, the expected dependence on the square root of time finally appears.
Antiferromagnetic order in single crystals of the S =2 quasi-one-dimensional chain MnCl3(bpy)
NASA Astrophysics Data System (ADS)
Shinozaki, Shin-ichi; Okutani, Akira; Yoshizawa, Daichi; Kida, Takanori; Takeuchi, Tetsuya; Yamamoto, Shoji; Risset, Olivia N.; Talham, Daniel R.; Meisel, Mark W.; Hagiwara, Masayuki
2016-01-01
A suite of experimental tools, including high-field magnetization and electron spin resonance (ESR) studies in magnetic fields of up to 50 T and heat capacity studies up to 9 T, have revealed antiferromagnetic order in single crystals of the Heisenberg S =2 chain compound MnCl3(bpy), where bpy is 2 ,2'-bipyridine . The Néel temperature, which depends on the strength of the applied magnetic field and its orientation with respect to the crystalline axes that was revealed by heat capacity measurements, is near 11.5 K in zero field. The spin-flop transition is identified in the magnetization curve acquired at 1.7 K and at μoHSFc=24 T along the c axis. The transition field HSF is lower than that expected from the previous antiferromagnetic resonance (AFMR) studies on a powder sample. The identification of the long-range antiferromagnetic order resolves an earlier report by Granroth et al. [Phys. Rev. Lett. 77, 1616 (1996)], 10.1103/PhysRevLett.77.1616 that identified MnCl3(bpy) as an S =2 Haldane system down to 40 mK. The ESR studies identify a wide range of antiferromagnetic resonance modes that provide additional microscopic information about the g values (ga*=2.09 , gb=1.92 , and gc=2.07 ), the zero-field splitting constants, D /kB=-1.5 K and E /kB=-0.17 K when the nearest-neighbor spin interaction J /kB=31.2 K, which is evaluated from fitting the susceptibility, and the anisotropy of this compound (easy axis is the c axis, the second easy-axis is the b axis, and the hard axis is the a* axis), when using a standard (two-sublattice) AFMR analysis that does not quantitatively reproduce the observed HSFc value. The observed resonance mode indicates the frequency minimum at HSFc.
NASA Astrophysics Data System (ADS)
Bagatskii, M. I.; Sumarokov, V. V.; Barabashko, M. S.
2016-02-01
The heat capacity at constant pressure CP of 1D-chains of methane molecules adsorbed in the grooves on the outer surface of the bundles of closed single-walled nanotubes was measured in the temperature range from 2 to 60 K for the first time. The behavior of the temperature dependence of CP below 12 K indicates the presence of a Schottky-type anomaly originated from the tunneling between the lowest energy levels of the rotational spectra of the A, T, and E nuclear-spin species of methane molecules. The feature observed in the vicinity of 14 K is presumably caused by an orientational phase transition, in which the nature of the rotational motion of the molecules changes from libration to hindered rotation. It was found that the rotational heat capacity in the temperature range of 30-40 K is close to that of freely rotating methane molecules. An increase in the derivative dCP(T)/dT above 40 K and the feature in the CP(T) near 52 K are due to the decay of 1D chains of CH4.
Slave fermion formalism for the tetrahedral spin chain
NASA Astrophysics Data System (ADS)
Mohan, Priyanka; Rao, Sumathi
2016-09-01
We use the SU(2) slave fermion approach to study a tetrahedral spin 1/2 chain, which is a one-dimensional generalization of the two dimensional Kitaev honeycomb model. Using the mean field theory, coupled with a gauge fixing procedure to implement the single occupancy constraint, we obtain the phase diagram of the model. We then show that it matches the exact results obtained earlier using the Majorana fermion representation. We also compute the spin-spin correlation in the gapless phase and show that it is a spin liquid. Finally, we map the one-dimensional model in terms of the slave fermions to the model of 1D p-wave superconducting model with complex parameters and show that the parameters of our model fall in the topological trivial regime and hence does not have edge Majorana modes.
Zvonarev, M B; Cheianov, V V; Giamarchi, T
2009-09-11
We investigate the dynamics of the one-dimensional strongly repulsive spin-1/2 Bose-Hubbard model for filling nu
NASA Astrophysics Data System (ADS)
Kirihara, Akihiro; Kondo, Koichi; Ishida, Masahiko; Ihara, Kazuki; Iwasaki, Yuma; Someya, Hiroko; Matsuba, Asuka; Uchida, Ken-Ichi; Saitoh, Eiji; Yamamoto, Naoharu; Kohmoto, Shigeru; Murakami, Tomoo
2016-03-01
Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a Ni0.2Zn0.3Fe2.5O4 film which was formed on a flexible plastic sheet using a spray-coating method known as “ferrite plating”. The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin-current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management.
Kirihara, Akihiro; Kondo, Koichi; Ishida, Masahiko; Ihara, Kazuki; Iwasaki, Yuma; Someya, Hiroko; Matsuba, Asuka; Uchida, Ken-ichi; Saitoh, Eiji; Yamamoto, Naoharu; Kohmoto, Shigeru; Murakami, Tomoo
2016-01-01
Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a Ni0.2Zn0.3Fe2.5O4 film which was formed on a flexible plastic sheet using a spray-coating method known as “ferrite plating”. The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin-current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management. PMID:26975208
Kirihara, Akihiro; Kondo, Koichi; Ishida, Masahiko; Ihara, Kazuki; Iwasaki, Yuma; Someya, Hiroko; Matsuba, Asuka; Uchida, Ken-ichi; Saitoh, Eiji; Yamamoto, Naoharu; Kohmoto, Shigeru; Murakami, Tomoo
2016-03-15
Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a Ni0.2Zn0.3Fe2.5O4 film which was formed on a flexible plastic sheet using a spray-coating method known as "ferrite plating". The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin-current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management.
Quasi-local conserved charges and spin transport in spin-1 integrable chains
NASA Astrophysics Data System (ADS)
Piroli, Lorenzo; Vernier, Eric
2016-05-01
We consider the integrable one-dimensional spin-1 chain defined by the Zamolodchikov-Fateev (ZF) Hamiltonian. The latter is parametrized, analogously to the XXZ spin-1/2 model, by a continuous anisotropy parameter and at the isotropic point coincides with the well-known spin-1 Babujian-Takhtajan Hamiltonian. Following a procedure recently developed for the XXZ model, we explicitly construct a continuous family of quasi-local conserved operators for the periodic spin-1 ZF chain. Our construction is valid for a dense set of commensurate values of the anisotropy parameter in the gapless regime where the isotropic point is excluded. Using the Mazur inequality, we show that, as for the XXZ model, these quasi-local charges are enough to prove that the high-temperature spin Drude weight is non-vanishing in the thermodynamic limit, thus establishing ballistic spin transport at high temperature.
Entanglement in Nonunitary Quantum Critical Spin Chains
NASA Astrophysics Data System (ADS)
Couvreur, Romain; Jacobsen, Jesper Lykke; Saleur, Hubert
2017-07-01
Entanglement entropy has proven invaluable to our understanding of quantum criticality. It is natural to try to extend the concept to "nonunitary quantum mechanics," which has seen growing interest from areas as diverse as open quantum systems, noninteracting electronic disordered systems, or nonunitary conformal field theory (CFT). We propose and investigate such an extension here, by focusing on the case of one-dimensional quantum group symmetric or supergroup symmetric spin chains. We show that the consideration of left and right eigenstates combined with appropriate definitions of the trace leads to a natural definition of Rényi entropies in a large variety of models. We interpret this definition geometrically in terms of related loop models and calculate the corresponding scaling in the conformal case. This allows us to distinguish the role of the central charge and effective central charge in rational minimal models of CFT, and to define an effective central charge in other, less well-understood cases. The example of the s l (2 |1 ) alternating spin chain for percolation is discussed in detail.
Inverse design of disordered stealthy hyperuniform spin chains
NASA Astrophysics Data System (ADS)
Chertkov, Eli; DiStasio, Robert A.; Zhang, Ge; Car, Roberto; Torquato, Salvatore
2016-02-01
Positioned between crystalline solids and liquids, disordered many-particle systems which are stealthy and hyperuniform represent new states of matter that are endowed with novel physical and thermodynamic properties. Such stealthy and hyperuniform states are unique in that they are transparent to radiation for a range of wave numbers around the origin. In this work, we employ recently developed inverse statistical-mechanical methods, which seek to obtain the optimal set of interactions that will spontaneously produce a targeted structure or configuration as a unique ground state, to investigate the spin-spin interaction potentials required to stabilize disordered stealthy hyperuniform one-dimensional (1D) Ising-type spin chains. By performing an exhaustive search over the spin configurations that can be enumerated on periodic 1D integer lattices containing N =2 ,3 ,...,36 sites, we were able to identify and structurally characterize all stealthy hyperuniform spin chains in this range of system sizes. Within this pool of stealthy hyperuniform spin configurations, we then utilized such inverse optimization techniques to demonstrate that stealthy hyperuniform spin chains can be realized as either unique or degenerate disordered ground states of radial long-ranged (relative to the spin-chain length) spin-spin interactions. Such exotic ground states appear to be distinctly different from spin glasses in both their inherent structural properties and the nature of the spin-spin interactions required to stabilize them. As such, the implications and significance of the existence of these disordered stealthy hyperuniform ground-state spin systems warrants further study, including whether their bulk physical properties and excited states, like their many-particle system counterparts, are singularly remarkable, and can be experimentally realized.
Field dependent spin transport of anisotropic Heisenberg chain
NASA Astrophysics Data System (ADS)
Rezania, H.
2016-04-01
We have addressed the static spin conductivity and spin Drude weight of one-dimensional spin-1/2 anisotropic antiferromagnetic Heisenberg chain in the finite magnetic field. We have investigated the behavior of transport properties by means of excitation spectrum in terms of a hard core bosonic representation. The effect of in-plane anisotropy on the spin transport properties has also been studied via the bosonic model by Green's function approach. This anisotropy is considered for exchange constants that couple spin components perpendicular to magnetic field direction. We have found the temperature dependence of the spin conductivity and spin Drude weight in the gapped field induced spin-polarized phase for various magnetic field and anisotropy parameters. Furthermore we have studied the magnetic field dependence of static spin conductivity and Drude weight for various anisotropy parameters. Our results show the regular part of spin conductivity vanishes in isotropic case however Drude weight has a finite non-zero value and the system exhibits ballistic transport properties. We also find the peak in the static spin conductivity factor moves to higher temperature upon increasing the magnetic field at fixed anisotropy. The static spin conductivity is found to be monotonically decreasing with magnetic field due to increase of energy gap in the excitation spectrum. Furthermore we have studied the temperature dependence of spin Drude weight for different magnetic field and various anisotropy parameters.
Aspelmeier, T; Wang, Wenlong; Moore, M A; Katzgraber, Helmut G
2016-08-01
The one-dimensional Ising spin-glass model with power-law long-range interactions is a useful proxy model for studying spin glasses in higher space dimensions and for finding the dimension at which the spin-glass state changes from having broken replica symmetry to that of droplet behavior. To this end we have calculated the exponent that describes the difference in free energy between periodic and antiperiodic boundary conditions. Numerical work is done to support some of the assumptions made in the calculations and to determine the behavior of the interface free-energy exponent of the power law of the interactions. Our numerical results for the interface free-energy exponent are badly affected by finite-size problems.
NASA Astrophysics Data System (ADS)
Aspelmeier, T.; Wang, Wenlong; Moore, M. A.; Katzgraber, Helmut G.
2016-08-01
The one-dimensional Ising spin-glass model with power-law long-range interactions is a useful proxy model for studying spin glasses in higher space dimensions and for finding the dimension at which the spin-glass state changes from having broken replica symmetry to that of droplet behavior. To this end we have calculated the exponent that describes the difference in free energy between periodic and antiperiodic boundary conditions. Numerical work is done to support some of the assumptions made in the calculations and to determine the behavior of the interface free-energy exponent of the power law of the interactions. Our numerical results for the interface free-energy exponent are badly affected by finite-size problems.
Transferring information through a mixed-five-spin chain channel
NASA Astrophysics Data System (ADS)
Arian Zad, Hamid; Movahhedian, Hossein
2016-08-01
We initially introduce one-dimensional mixed-five-spin chain with Ising-XY model which includes mixture of spins-1/2 and spins-1. Here, it is considered that nearest spins (1,1/2) have Ising-type interaction and nearest spins (1/2,1/2) have both XY-type and Dzyaloshinskii-Moriya (DM) interactions together. Nearest spins (1,1) have XX Heisenberg interaction. This system is in the vicinity of an external homogeneous magnetic field B in thermal equilibrium state. We promote the quantum information transmitting protocol verified for a normal spin chain with simple model (refer to Rossini D, Giovannetti V and Fazio R 2007 Int. J. Quantum Infor. 5 439) (widely in reference: Giovannetti V and Fazio R 2005 Phys. Rev. A 71 032314) by means of considering the suggested mixed-five-spin chain as a quantum communication channel for transmitting both qubits and qutrits ideally. Hence, we investigate some useful quantities such as quantum capacity and quantum information transmission rate for the system. Finally, we conclude that, when the DM interaction between spins (1/2,1/2) increases the system is a more ideal channel for transmitting information.
Spatially Resolved Detection of a Spin-Entanglement Wave in a Bose-Hubbard Chain.
Fukuhara, Takeshi; Hild, Sebastian; Zeiher, Johannes; Schauß, Peter; Bloch, Immanuel; Endres, Manuel; Gross, Christian
2015-07-17
Entanglement is an essential property of quantum many-body systems. However, its local detection is challenging and was so far limited to spin degrees of freedom in ion chains. Here we measure entanglement between the spins of atoms located on two lattice sites in a one-dimensional Bose-Hubbard chain which features both local spin- and particle-number fluctuations. Starting with an initially localized spin impurity, we observe an outwards propagating entanglement wave and show quantitatively how entanglement in the spin sector rapidly decreases with increasing particle-number fluctuations in the chain.
NASA Astrophysics Data System (ADS)
Kou, Zhaoxia; Zhang, Wen; Wang, Yukun; Johnny Wong, Ping Kwan; Huang, Haibo; Ji, Cheng; Yue, Jinjin; Zhang, Dong; Zhai, Ya; Zhai, Hongru
2014-05-01
A series of zinc ferrite chains have been synthesized successfully by using the self-assembly method in different synthesizing magnetic fields. The particle chains are arranged in order on the Si substrate under the assistant magnetic field. The zinc ferrite chains show various length-to-radius aspect ratio, saturation magnetization Ms, remanent magnetization Mr, and coercivity Hc in the corresponding synthesizing magnetic fields. Using X-ray magnetic circular dichroism, the Zn substitution mechanism in the ferrite chains has been analyzed and discussed.
NASA Astrophysics Data System (ADS)
Chang, C.-P.; Chu, M.-W.; Jeng, H. T.; Cheng, S.-L.; Lin, J. G.; Yang, J.-R.; Chen, C. H.
2014-03-01
The success of semiconductor technology is largely ascribed to controlled impacts of strains and defects on the two-dimensional interfacial charges. Interfacial charges also appear in oxide heterojunctions such as LaAlO3/SrTiO3 and (Nd0.35Sr0.65)MnO3/SrTiO3. How the localized strain field of one-dimensional misfit dislocations, defects resulting from the intrinsic misfit strains, would affect the extended oxide-interfacial charges is intriguing and remains unresolved. Here we show the atomic-scale observation of one-dimensional electron chains formed in (Nd0.35Sr0.65)MnO3/SrTiO3 by the condensation of characteristic two-dimensional interfacial charges into the strain field of periodically arrayed misfit dislocations, using chemical mapping and quantification by scanning transmission electron microscopy. The strain-relaxed inter-dislocation regions are readily charge depleted, otherwise decorated by the pristine charges, and the corresponding total-energy calculations unravel the undocumented charge-reservoir role played by the dislocation-strain field. This two-dimensional-to-one-dimensional electronic condensation represents a novel electronic-inhomogeneity mechanism at oxide interfaces and could stimulate further studies of one-dimensional electron density in oxide heterostructures.
Mao, Yuliang; Zhong, JianXin; Yuan, JianMei; Zhao, Xinluo; Ando, Yoshinori
2006-05-01
Using first principles calculations, we investigate the atomic and electronic structure of carbon nanowires (CNWs) as the carbon chain inserted into single wall carbon nanotubes (SWCNTs). It indicates that the (5,5) CNW system exhibits metallic character, however, the insertion of carbon chain can transit a semi-conducting (9,0) SWCNT into a metallic.
Quantum Critical Spin-2 Chain with Emergent SU(3) Symmetry
NASA Astrophysics Data System (ADS)
Chen, Pochung; Xue, Zhi-Long; McCulloch, I. P.; Chung, Ming-Chiang; Huang, Chao-Chun; Yip, S.-K.
2015-04-01
We study the quantum critical phase of an SU(2) symmetric spin-2 chain obtained from spin-2 bosons in a one-dimensional lattice. We obtain the scaling of the finite-size energies and entanglement entropy by exact diagonalization and density-matrix renormalization group methods. From the numerical results of the energy spectra, central charge, and scaling dimension we identify the conformal field theory describing the whole critical phase to be the SU (3 )1 Wess-Zumino-Witten model. We find that, while the Hamiltonian is only SU(2) invariant, in this critical phase there is an emergent SU(3) symmetry in the thermodynamic limit.
NASA Astrophysics Data System (ADS)
Soltanieh-ha, Mohammad; Feiguin, Adrian E.
2014-10-01
The physics of the strongly interacting Hubbard chain (with t /U ≪1 ) at finite temperatures undergoes a crossover to a spin-incoherent regime when the temperature is very small relative to the Fermi energy, but larger than the characteristic spin energy scale. This crossover can be understood by means of Ogata and Shiba's factorized wave function, where charge and spin are totally decoupled, and assuming that the charge remains in the ground state, while the spin is thermally excited and at an effective "spin temperature." We use the time-dependent density matrix renormalization group method to calculate the dynamical contributions of the spin, to reconstruct the single-particle spectral function of the electrons. The crossover is characterized by a redistribution of spectral weight both in frequency and momentum, with an apparent shift by kF of the minimum of the dispersion.
Zhang, Shao-Liang; Zhao, Xin-Hua; Wang, Yuan-Min; Shao, Dong; Wang, Xin-Yi
2015-05-28
Four one-dimensional heterobimetallic coordination polymers {Fe(pic)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pic = 2-picolylamine), and {Fe(pypz)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pypz = 2-(1H-pyrazol-3-yl)pyridine) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction, magnetic measurements and differential scanning calorimetry (DSC). Single-crystal X-ray analyses show that all the compounds are 1D neutral zigzag chain structures in which the planar [M(CN)4](2-) anion acts as a μ2-bridging ligand, and the two pic/pypz molecules as chelating coligands. Examination of the intermolecular contacts in compounds reveals the existence of the hydrogen bonding interactions involving the hydrogen donor groups of the pic and pypz ligands and the nitrogen atoms of the non-bridging cyanide groups of the [M(CN)4](2-) anions. Weak π-π interactions were also found to be important for the formation of the 3D structures of compounds and . The SCO properties of all compounds were confirmed by the detailed structural analyses of the coordination environments of the Fe(II) centres, DSC analyses, and magnetic susceptibility measurements. Compounds and exhibit complete SCO behaviour with very narrow thermal hysteresis loops centred near the room temperature (T1/2↓ = 270 K and T1/2↑ = 272 K for and T1/2↓ = 272 K and T1/2↑ = 274 K for ), whereas and exhibit abrupt SCO at 186 and 180 K, respectively. Compared to the mononuclear species of the pic and pypz ligands, the SCO temperatures are adjusted by the different ligand field strength of the [M(CN)4)](2-) units. The cooperativity from both the coordination bonds and supramolecular interaction leads to the observation of the hysteresis loops in the Fe-pic systems and the abrupt SCO transition in the Fe-pypz systems. Furthermore, the light-induced excited-spin-state trapping (LIESST) effect was observed for .
Deformed Fredkin spin chain with extensive entanglement
NASA Astrophysics Data System (ADS)
Salberger, Olof; Udagawa, Takuma; Zhang, Zhao; Katsura, Hosho; Klich, Israel; Korepin, Vladimir
2017-06-01
We introduce a new spin chain which is a deformation of the Fredkin spin chain and has a phase transition between bounded and extensive entanglement entropy scaling. In this chain, spins have a local interaction of three nearest neighbors. The Hamiltonian is frustration-free and its ground state can be described analytically as a weighted superposition of Dyck paths that depends on a deformation parameter t. In the purely spin 1/2 case, whenever t\
Quantum signatures of breathers in a finite Heisenberg spin chain.
Djoufack, Z I; Kenfack-Jiotsa, A; Nguenang, J P; Domngang, S
2010-05-26
A map of a quantum Heisenberg spin chain into an extended Bose-Hubbard-like Hamiltonian is set up. Within this framework, the spectrum of the corresponding Bose-Hubbard chain, on a periodic one-dimensional lattice containing two, four, and six bosons shows interesting detailed band structures. These fine structures are studied using numerical diagonalization, and nondegenerate and degenerate perturbation theory. We also focus our attention on the effect of the anisotropy and Heisenberg exchange energy on the detailed band structures. The signature of the quantum breather is also set up by the square of the amplitudes of the corresponding eigenvectors in real space.
NASA Astrophysics Data System (ADS)
Elliott, Jeffrey Holden
This thesis reports on three separate investigations in solid state physics. The first is electron paramagnetic resonance in the spin glass Ag:Mn. EPR measurements were performed at two resonance frequencies, concentrating on temperatures above the glass transition temperature. The measured linewidth appears to diverge at T(,g) for low resonance frequencies. This is the first observation of a sharp feature in the EPR behavior of spin glasses at the magnetic susceptibility transition temperature. These results will be compared with recently proposed phenomenological and microscopic theories. The second topic reported in this thesis is the superconducting transition of thin aluminum films. These films were investigated as a function of grain size and thickness. The transition temperature was enhanced over the bulk value, in agreement with many previous investigations of granular aluminum. This study differs from most in the sample preparation--evaporation, photolithography and anodization. This allows a better understanding of the sample geometry on the level of a grain size, which in turn allows better comparison to the many theories proposed to explain the enhancement. The third topic reported in this thesis is an extension of the variable rate hopping theory applied in one dimension to N-ME-Qn(TCNQ)(,2). This model is a classical one used to explain both the DC and AC electrical conductivity of organic conductors. The temperature dependence of the model does not agree with experiment at low temperatures. Tunneling has been added to the hopping. This increases the conductivity at low temperatures, and results in excellent agreement with the experimental conductivity over the measured temperature range. The model also predicts that the frequency dependence of the conductivity varies as (omega)(' 1/2) at low frequencies. This long time tail prediction agrees with the measured dielectric constant of N-Me-iso-Qn(TCNQ)(,2).
Otake, Ken-ichi; Otsubo, Kazuya; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kitagawa, Hiroshi
2016-03-07
One-dimensional (1D) electronic systems have attracted significant attention for a long time because of their various physical properties. Among 1D electronic systems, 1D halogen-bridged mixed-valence transition-metal complexes (the so-called MX chains) have been thoroughly studied owing to designable structures and electronic states. Here, we report the syntheses, structures, and electronic properties of three kinds of novel neutral MX-chain complexes. The crystal structures consist of 1D chains of Pt-X repeating units with (1R,2R)-(-)-diaminocychlohexane and CN(-) in-plane ligands. Because of the absence of a counteranion, the neutral MX chains have short interchain distances, so that strong interchain electronic interaction is expected. Resonance Raman spectra and diffuse-reflectance UV-vis spectra indicate that their electronic states are mixed-valence states (charge-density-wave state: Pt(2+)···X-Pt(4+)-X···Pt(2+)···X-Pt(4+)-X···). In addition, the relationship between the intervalence charge-transfer (IVCT) band gap and the degree of distortion of the 1D chain shows that the neutral MX chains have a larger IVCT band gap than that of cationic MX-chain complexes. These results provide new insight into the physical and electronic properties of 1D chain compounds.
NASA Astrophysics Data System (ADS)
Bolens, Adrien; Katsura, Hosho; Ogata, Masao; Miyashita, Seiji
2017-06-01
We study how the synergetic effect of spin-orbit coupling (SOC) and Zeeman splitting (ZS) affects the optical conductivity in the one-dimensional Hubbard model using the Kubo formula. We focus on two phenomena: (1) the electric dipole spin resonance (EDSR) in the metallic regime and (2) the optical conductivity in the Mott-insulating phase above the optical gap. In both cases, we calculate qualitatively the effects of SOC and ZS and how they depend on the relative angle between the SOC vector and the magnetic field direction. First, we investigate the spin resonance without electron correlation (the Hubbard parameter U =0 ). Although, neither SOC nor ZS causes any resonance by itself in the optical conductivity, the EDSR becomes possible when both of them exist. The resulting contribution to the optical conductivity is analyzed analytically. The effect of U on the spin resonance is also studied with a numerical method. It is found that at half filling, the resonance is first enhanced for small U and then suppressed when the optical gap is large enough. In the strong coupling limit U →∞ at half filling, we also refer to the resonance between the lower and upper Hubbard bands appearing at ω ˜U , above the optical gap. A large magnetic field tends to suppress the signal while it is recovered thanks to SOC depending on the relative angle of the magnetic field.
Yu, Fei; Li, Dan-Dan; Cheng, Lin; Yin, Zheng; Zeng, Ming-Hua; Kurmoo, Mohamedally
2015-02-16
In search of porous materials for selective sorption and iodine inclusion, we have found two networks made of chains with a kink at the metal nodes held together by supramolecular interactions (H-bond and π···π stacking). The solvent can be removed and replaced reversibly without loss of crystallinity, as demonstrated by single-crystal-to-single-crystal crystallography. In contrast, iodine uptake degrades the crystallinity to amorphous, and it regains its crystalline state after removal of the iodine at 200 °C. Slight differences in behavior of the sorption and inclusion properties between the tetrahedral metal nodes, Zn and Co, are associated with the size of the nodes. An important feature is the extent of iodine that can be included between the chains that is doubled with temperature from 30 to 100 °C and exceeds the weight in mass of the compounds.
One-Dimensional Stacking Disorder in a Linear Chain Compound (CH3)3NHCdCl3
NASA Astrophysics Data System (ADS)
Fukumoto, Toshiro; Kashida, Shoji
1985-10-01
The structural phase transition of a linear chain compound (CH3)3NHCdCl3 (TrMCC) was studied by X-ray diffraction method. Accompanying the phase transition from the (1×\\sqrt{3}) structure to the (2×\\sqrt{3}) structure, strong diffuse streaks were observed along the \\mbi{b}* direction. In order to explain the observed peak profiles, a simplified model was presented. In this model, the layers made of rather tightly coupled CdCl3 chains were assumed to stack with probabilities. The diffraction intensity was analyzed using the matrix method given by Kakinoki and Komura. The calculation which incorporates the effect of the phase shift due to the displacements normal to the stacking direction was found to reproduce the experimental results fairly well. The streaks observed in the (3× 2) phase were also discussed.
One-dimensional decavanadate chains in the crystal structure of Rb4[Na(H2O)6][HV10O28]·4H2O.
Yakubovich, Olga V; Steele, Ian M; Yakovleva, Ekaterina V; Dimitrova, Olga V
2015-06-01
New decavanadate minerals, the products of the leaching or metasomatic processes, are possible in nature via Na/Rb removal/inclusion reactions. As part of our search for novel vanadate phases with varying functionalities, a new phase, tetrarubidium hexaaquasodium hydrogen decavanadate tetrahydrate, Rb4[Na(H2O)6][HV10O28]·4H2O, has been synthesized by the hydrothermal technique at 553 K. Ten shared edges of V-centred octahedra form monoprotonated decavanadate cages, which are joined together via hydrogen bonds into one-dimensional chains parallel to the [101] direction. Within these chains, H atoms are sandwiched between neighbouring polyanions. Na and Rb atoms and H2O molecules occupy interstices flanked by the anionic chains providing additional crosslinking in the structure. This compound is the second decavanadate with P2/n symmetry. Structural relationships among protonated and deprotonated decavanadates with inorganic cations, including minerals of the pascoite group, are discussed.
Zhou, Jing; Li, Yan; Zahl, Percy; Sutter, Peter; Stacchiola, Dario J.; White, Michael G.
2015-03-14
The morphology and electronic structure of vapor deposited 4,4′-biphenyldiisocyanide (BPDI) on a Au(111) surface were investigated using variable-temperature scanning tunneling microscopy. When deposited at room temperature, BPDI molecules form one-dimensional molecular chains similar to that recently observed for the structurally related 1,4-phenyl diisocyanide (PDI). Compared to PDI, the longer periodicity for the BPDI molecular chains is consistent with the addition of a second phenyl ring and supports a structural model in which the BPDI molecules lie parallel to the surface and interconnected by Au-adatoms. The molecular chains are mostly aligned along the [11{sup -}0] direction of the Au(111) substrate, but exhibit frequent changes in angle that are consistent with directions between fcc and hcp three-fold hollow sites. Dispersion-corrected density functional theory calculations for one-dimensional chains of BPDI molecules bound end-to-end via their isocyanide groups to Au-adatoms reproduce the observed periodicity of the chains and show that this morphology is energetically favored over upright binding with one free —NC group. The spatially resolved conductance (dI/dV) map for BPDI on Au(111) exhibits a feature centered at −0.67 eV below the Fermi level which are delocalized along the chain with maxima at the Au-adatom and biphenyl positions. This occupied resonant feature is close to that previously observed for the PDI in both photoemission and conductance measurements and is attributed to an occupied interfacial state resulting from BPDI-Au interactions.
NASA Astrophysics Data System (ADS)
de Lima, Raimundo Alexandre; Tsallis, Constantino
1983-06-01
We study in detail, within the adiabatic approximation for the structural degrees of freedom and on exact grounds for the magnetic ones, the d=1 magnetostrictive spin- 1/2 XY model in the presence of an external magnetic field along the z axis. We calculate the specific heat, magnetization, isothermal susceptibility, and the structural order parameter and spectrum (including the sound velocity). The system presents, in temperature-field space, three structurally different phases: the uniform (U), the dimerized (D), and the modulated (M) phases (the latter can be either commensurate or incommensurate with the other two). The critical frontiers U-D and U-M are of the second-order type while the D-M one is of the first-order type; all three join at a Lifshitz point. The U-M frontier presents a new type of multicritical point on which the frozen structural wave vector vanishes. The phase diagram is quite anomalous for high values of the elastic constant. Several other effects are predicted. The present theory is expected to be applicable to substances like TTF-BDT [tetrathiafulvalinium bis-cis-(1,2-perfluoromethylethylene-1,2-diselenolato)-metal], MEM(TCNQ)2 (N-methyl-N-ethyl-morpholinium ditetracyanoquinodimethanide), and eventually the alkali-metal tetracyanoquinodimethanides (TCNQ).
Ikeuchi, Satoaki; Miyazaki, Yuji; Takeda, Sadamu; Akutagawa, Tomoyuki; Nishihara, Sadafumi; Nakamura, Takayoshi; Saito, Kazuya
2005-07-22
Heat capacity of Cs2(18-crown-6)3[Ni(dmit)2]2 was measured by adiabatic calorimetry. A broad thermal anomaly was observed around 225 K. The entropy gain (about 52 J K(-1) mol(-1)) is much larger than that expected for twofold disordering of 18-crown-6 assumed in the previous structure analysis. The shape of thermal anomaly was qualitatively explained by a linear Ising model developed for cooperative disordering in polymers. The 18-crown-6 molecules forming a one-dimensional chain in the crystal are orientationally disordered with moderate cooperativity.
Spin chains and string theory.
Kruczenski, Martin
2004-10-15
Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.
Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains
Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han
2016-01-01
We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γnTc) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower Tc, compared to that of Ta4Pd3Te16, may be attributed to the lower density of states. PMID:26876362
Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains.
Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han
2016-02-15
We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γ(n)T(c)) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower T(c), compared to that of Ta4Pd3Te16, may be attributed to the lower density of states.
Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains
NASA Astrophysics Data System (ADS)
Jiao, Wen-He; He, Lan-Po; Liu, Yi; Xu, Xiao-Feng; Li, Yu-Ke; Zhang, Chu-Hang; Zhou, Nan; Xu, Zhu-An; Li, Shi-Yan; Cao, Guang-Han
2016-02-01
We report bulk superconductivity at 1.0 K in a low-dimensional ternary telluride Ta3Pd3Te14 containing edge-sharing PdTe2 chains along crystallographic b axis, similar to the recently discovered superconductor Ta4Pd3Te16. The electronic heat capacity data show an obvious anomaly at the transition temperature, which indicates bulk superconductivity. The specific-heat jump is ΔC/(γnTc) ≈ 1.35, suggesting a weak coupling scenario. By measuring the low-temperature thermal conductivity, we conclude that Ta3Pd3Te14 is very likely a dirty s-wave superconductor. The emergence of superconductivity in Ta3Pd3Te14 with a lower Tc, compared to that of Ta4Pd3Te16, may be attributed to the lower density of states.
NASA Astrophysics Data System (ADS)
Wu, Xianxin; Yang, Fan; Le, Congcong; Yuan, Jing; Qin, Shengshan; Fan, Heng; Hu, Jiangping
The recently discovered quasi-one dimensional superconductors A2Cr3As3(A=K,Rb,Cs), are found to possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. Then, we find that the triplet pz-wave pairing is strongly favored. Finally, with pz wave pairing state, we obtain the specific heat, superfluid density, Knight shift and spin relaxation rate and find that all these properties at low temperature (T <
NASA Astrophysics Data System (ADS)
Herak, Mirta; Žilić, Dijana; Matković Čalogović, Dubravka; Berger, Helmuth
2015-05-01
The antiferromagnetically ordered state of the monoclinic quasi-one-dimensional S =1 /2 Heisenberg antiferromagnet CuSb2O6 was studied combining torque magnetometry with a phenomenological approach to magnetic anisotropy. This system is known to have a number of different twins in the monoclinic β phase, which differ in the orientation of the two CuO6 octahedra in the unit cell resulting in different orientation of magnetic axes with respect to crystal axes for each twin. We performed torque measurements in magnetic fields H ≤0.8 T on a sample where a certain type of twin was shown to be dominant by ESR spectroscopy. The measured data reveal that the easy axis is the crystallographic b axis for this sample. Phenomenological magnetocrystalline anisotropy energy invariant to crystal symmetry operations was used to model the spin axis direction in zero and finite magnetic fields. Our model reproduces the value of the spin-flop field HSF=1.25 T found in literature. A combination of this approach with our torque results shows that the spin axis will flop in the direction of the maximal value of measured g tensor when the magnetic field H >HSF is applied along the easy axis direction. Our analysis of magnetocrystalline anisotropy energy predicts two possibilities for the easy axis direction in this system, b or a , connected to different crystallographic twins that can be realized in CuSb2O6 . These results offer a possibility to reconcile the different reports of easy axis direction found in literature for this system and also nicely demonstrate how a combination of torque magnetometry and a phenomenological approach to magnetic anisotropy can be used to determine the value of the spin-flop field and the direction of spin axis in antiferromagnets in both H
NASA Astrophysics Data System (ADS)
Zornoza, P.; Petukhov, K.; Dressel, M.; Biskup, N.; Vuletić, T.; Tomić, S.
2005-07-01
The anisotropic and non-linear transport properties of the quasi one-dimensional organic conductor (TMTSF)2PF6 have been studied by dc, radiofrequency, and microwave methods. Microwave experiments along all three axes reveal that collective transport, which is considered to be the fingerprint of the spin-density-wave condensate, also occurs in the perpendicular b' direction. The pinned mode resonance is present in the a and b'-axes response, but not along the least conducting c* direction. The ac-field threshold, above which the spin-density-wave response is non-linear, strongly decreases as the temperature drops below 4 K. With increasing strength of the microwave electric field and of the radiofrequency signal, the pinned mode and the screened phason loss-peak shift to lower frequencies. In the non-linear regime, in addition to the phason relaxation mode with Arrhenius-like resistive decay, an additional mode with very long and temperature-independent relaxation time appears below 4 K. We attribute the new process to short-wavelength excitations associated with discommensurations of the spin density wave close to commensurability.
NASA Astrophysics Data System (ADS)
Platt, Christian; Cho, Weejee; McKenzie, Ross H.; Thomale, Ronny; Raghu, S.
2016-06-01
Previous theoretical studies [W. Cho, C. Platt, R. H. McKenzie, and S. Raghu, Phys. Rev. B 92, 134514 (2015), 10.1103/PhysRevB.92.134514; N. Lera and J. V. Alvarez, Phys. Rev. B 92, 174523 (2015), 10.1103/PhysRevB.92.174523] have suggested that Li0.9Mo6O17 , a quasi-one-dimensional "purple bronze" compound, exhibits spin-triplet superconductivity and that the gap function changes sign across the two nearly degenerate Fermi surface sheets. We investigate the role of spin-orbit coupling (SOC) in determining the symmetry and orientation of the d vector associated with the superconducting order parameter. We propose that the lack of local inversion symmetry within the four-atom unit cell leads to a spin-orbit coupling analogous to that proposed for graphene, MoS2, or SrPtAs. In addition, from a weak-coupling renormalization group treatment of an effective model Hamiltonian, we find that SOC favors the odd parity A1 u state with Sz=±1 over the B states with Sz=0 , where z denotes the least-conducting direction. We discuss possible definitive experimental signatures of this superconducting state.
Swanson, B. I.; Donohoe, R. J.; Worl, L. A.; Bulou, A. D.F.; Arrington, C. A.; Gammel, J. T.; Saxena, A.; Bishop, A. R.
1990-01-01
We have undertaken a combined theoretical and experimental effort directed toward the examination of both the ground and defect states in halide-bridged mixed-valence metal linear chains materials as they are tuned within and between broken symmetry phases. Novel low-dimensional highly correlated electronic materials offer a difficult theoretical challenge as we must span from a description of electronic structure on a molecular scale to the meso scale structure that is intrinsic to these solids. Our theoretical effort at Los Alamos combines quantum chemistry, band structure calculations, and many body modeling using Peierls-Hubbard Hamiltonians in order to model ground and local states. The experimental effort combines synthesis and a variety of microscopic structural and spectroscopic probes and macroscopic measurements in an effort to fully characterize both ground and local states as these materials are tuned in the phase boundary regions between broken symmetry states. The present article summarizes some of our recent research using optical spectroscopy to obtain signatures of photoexcited and intrinsic local states and compares these experimental results with Peierls-Hubbard calculations of the optical properties of these materials. Details concerning the theoretical and experimental approaches can be found elsewhere.
Dynamics of Composite Haldane Spin Chains in IPA-CuCl_{3}
Masuda, Takatsugu; Zheludev, Andrey I; Manaka, H.; Regnault, L.-P.; Chung, J.-H.; Qiu, Y.
2006-01-01
Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl{sub 3} are studied by cold neutron inelastic scattering. Strongly dispersive gap excitations are observed. Contrary to previously proposed models, the system is best described as an asymmetric quantum spin ladder. The observed spectrum is interpreted in terms of composite Haldane spin chains. The key difference from actual S = 1 chains is a sharp cutoff of the single-magnon spectrum at a certain critical wave vector.
NASA Astrophysics Data System (ADS)
Ito, Hiroshi; Asai, Takayuki; Shimizu, Yasuhiro; Hayama, Hiromi; Yoshida, Yukihiro; Saito, Gunzi
2016-07-01
We report an antiferromagnetic (AF) ordering at ambient pressure and a superconducting transition under pressure for κ - (ET) 2C F3S O3 [ ET =bis (ethylenedithio)tetrathiafulvalene], which has a two-dimensional electronic system with quasi-one-dimensional triangular spin lattice. At ambient pressure, AF ordering was detected at TN=2.5 K by 1H NMR, subsequent to two structural phase transitions at 230 and 190 K. Under hydrostatic pressures, metallic behavior appeared above ˜1.1 GPa, and a superconducting transition (maximum onset Tc=4.8 K at ˜1.3 GPa) was observed up to 2.2 GPa. Superconductivity was also found under c -axis strain, which reduced t'/t , but was absent under b -axis strain which increased t'/t .
NASA Astrophysics Data System (ADS)
Bhatt, Pramod; Mukadam, M. D.; Meena, S. S.; Mishra, S. K.; Mittal, R.; Sastry, P. U.; Mandal, B. P.; Yusuf, S. M.
2017-03-01
The ferroelectric materials are mainly focused on pure inorganic oxides; however, the organic molecule based materials have recently attracted great attention because of their multifunctional properties. The mixing of oxalate and phenanthroline ligands with metal ions (Fe or Mn) at room temperature followed by hydrothermal treatment results in the formation of one-dimensional single chain molecular magnets which exhibit room temperature dielectric and ferroelectric behavior. The compounds are chiral in nature, and exhibit a ferroelectric behavior, attributed to the polar point group C2, in which they crystallized. The compounds are also associated with a dielectric loss and thus a relaxation process. The observed electric dipole moment, essential for a ferroelectricity, has been understood quantitatively in terms of lattice distortions at two different lattice sites within the crystal structure. The studied single chain molecular magnetic materials with room temperature ferroelectric and dielectric properties could be of great technological importance in non-volatile memory elements, and high-performance insulators.
Superadiabatic quantum state transfer in spin chains
NASA Astrophysics Data System (ADS)
Agundez, R. R.; Hill, C. D.; Hollenberg, L. C. L.; Rogge, S.; Blaauboer, M.
2017-01-01
In this paper we propose a superadiabatic protocol where quantum state transfer can be achieved with arbitrarily high accuracy and minimal control across long spin chains with an odd number of spins. The quantum state transfer protocol only requires the control of the couplings between the qubits on the edge and the spin chain. We predict fidelities above 0.99 for an evolution of nanoseconds using typical spin-exchange coupling values of μ eV . Furthermore, by building a superadiabatic formalism on top of this protocol, we propose an effective superadiabatic protocol that retains the minimal control over the spin chain and further improves the fidelity.
Thermalization of a dimerized antiferromagnetic spin chain.
Konstantinidis, N P
2016-01-20
Thermalization is investigated for the one-dimensional anisotropic antiferromagnetic Heisenberg model with dimerized nearest-neighbor interactions that break integrability. For this purpose the time evolution of local operator expectation values after an interacting quench is calculated directly with the Chebyshev polynomial expansion, and the deviation of the diagonal from the canonical thermal ensemble value is calculated for increasing system size for these operators. The spatial and spin symmetries of the Hamiltonian are taken into account to divide it into symmetry subsectors. The rate of thermalization is found to weaken with the dimerization parameter as the Hamiltonian evolves between two integrable limits, the non-dimerized and the fully dimerized where the chain breaks up into isolated dimers. This conclusion is supported by the distribution of the local operator off-diagonal elements between the eigenstates of the Hamiltonian with respect to their energy difference, which determines the strength of temporal fluctuations. The off-diagonal elements have a low-energy peak for small dimerization which facilitates thermalization, and originates in the reduction of spatial symmetry with respect to the non-dimerized limit. For increasing dimerization their distribution changes and develops a single low-energy maximum that relates to the fully dimerized limit and slows down thermalization.
NASA Astrophysics Data System (ADS)
De, Santanu; Kumar, Kranti; Banerjee, A.; Chaddah, P.
2016-05-01
We have found that the geometrically frustrated spin chain compound Ca3Co2O6 belonging to Ising like universality class with uniaxial anisotropy shows kinetic arrest of first order intermediate phase (IP) to ferrimagnetic (FIM) transition. In this system, dc magnetization measurements followed by different protocols suggest the coexistence of high temperature IP with equilibrium FIM phase in low temperature. Formation of metastable state due to hindered first order transition has also been probed through cooling and heating in unequal field (CHUF) protocol. Kinetically arrested high temperature IP appears to persist down to almost the spin freezing temperature in this system.
NASA Astrophysics Data System (ADS)
Nocera, A.; Soltanieh-ha, M.; Perroni, C. A.; Cataudella, V.; Feiguin, A. E.
2014-11-01
We calculate the spectral function of the one-dimensional Hubbard-Holstein model using the time-dependent density matrix renormalization group, focusing on the regime of large local Coulomb repulsion, and away from electronic half-filling. We argue that, from weak to intermediate electron-phonon coupling, phonons interact only with the electronic charge, and not with the spin degrees of freedom. For strong electron-phonon interaction, spinon and holon bands are not discernible anymore and the system is well described by a spinless polaronic liquid. In this regime, we observe multiple peaks in the spectrum with an energy separation corresponding to the energy of the lattice vibrations (i.e., phonons). We support the numerical results by introducing a well controlled analytical approach based on Ogata-Shiba's factorized wave function, showing that the spectrum can be understood as a convolution of three contributions, originating from charge, spin, and lattice sectors. We recognize and interpret these signatures in the spectral properties and discuss the experimental implications.
NASA Astrophysics Data System (ADS)
Fatollahi, Amir H.
2017-03-01
The general theoretical ground for models based on compact angle coordinates is presented. It is observed that the proper dependence on compact coordinates has to be through the group elements and is achieved most naturally in a discrete-time formulation of the theory. By the construction, the discrete worldline inlaid by compact coordinates resembles the spin chains of magnetic systems. As examples, the models based on the groups U(1), Z_N and SU(2) are explicitly constructed and their exact energy spectra are obtained. As the consequence of the minima in the spectra, the models exhibit a phase transition of first order. We attempt to fit the dynamics by the U(1) group to the proposed role for monopoles in the dual Meissner effect of the confinement mechanism.
A one-dimensional double-chain coordination polymer: [Mn(C12H13NO6S)(C10H8N2)]n.
Liang, Fu-Pei; Chen, Man-Sheng; Hu, Rui-Xiang; Chen, Zi-Lu
2004-06-01
In the title compound, poly[[(2,2'-bipyridine-kappa(2)N,N')manganese(II)]-micro(3)-N-tosyl-L-glutamato-kappa(4)O,O':O":O"'], [Mn(tsgluo)(bipy)](n), where tsgluo is N-tosyl-L-glutamate (C(12)H(13)NO(6)S) and bipy is 2,2'-bipyridine (C(10)H(8)N(2)), the Mn atoms are octahedrally coordinated by two N atoms of one bipy ligand and by four O atoms of three tsgluo(2-) anions. The gamma-carboxyl group coordinates to the Mn(II) atom in a chelating mode, while the alpha-carboxyl group coordinates in a bidentate-bridging mode. The complex displays a one-dimensional double-chain structure.
Bethe vectors for XXX-spin chain
NASA Astrophysics Data System (ADS)
Burdík, Čestmír; Fuksa, Jan; Isaev, Alexei
2014-11-01
The paper deals with algebraic Bethe ansatz for XXX-spin chain. Generators of Yang-Baxter algebra are expressed in basis of free fermions and used to calculate explicit form of Bethe vectors. Their relation to N-component models is used to prove conjecture about their form in general. Some remarks on inhomogeneous XXX-spin chain are included.
NASA Astrophysics Data System (ADS)
Georgiev, Ivan T.; McKay, Susan R.
2001-03-01
We present a position-space renormalization-group method for nonequilibrium systems, and illustrate its application using the one-dimensional driven asymmetric chain. The dynamics in this case are characterized by three parameters: the probability α that a particle will enter the chain from the left boundary, the probability β that a particle will exit the chain at the right boundary, and the probability p that a particle will jump to its right neighboring site if that site is empty. Rescaling trajectories flow in the space of these probabilities and the dynamics are implemented sequentially. The phase diagram for the steady states consists of three distinct regions, one with high current and two others distinguished by their average densities. This method yields a multicritical point at α_c=β_c=0.5, in agreement with the exact solution.(B. Derrida, et al., J. Phys. A: Math. Gen. 26), 1493 (1993); G. Schutz and E. Domany, J. Stat. Phys. 72, 277 (1993). We find the exponent ν = 2.71 associated with this fixed point, as compared with the exact value of 2.00.
Chaotic dynamics of Heisenberg ferromagnetic spin chain with bilinear and biquadratic interactions
NASA Astrophysics Data System (ADS)
Blessy, B. S. Gnana; Latha, M. M.
2017-10-01
We investigate the chaotic dynamics of one dimensional Heisenberg ferromagnetic spin chain by constructing the Hamiltonian equations of motion. We present the trajectory and phase plots of the system with bilinear and also biquadratic interactions. The stability of the system is analysed in both cases by constructing the Jacobian matrix and by measuring the Lyapunov exponents. The results are illustrated graphically.
Transport of spin qubits with donor chains under realistic experimental conditions
NASA Astrophysics Data System (ADS)
Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; Rahman, Rajib; Klimeck, Gerhard; Morello, Andrea
2016-07-01
The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO2 interface. We then estimate the required time scales and exchange couplings, and the level of noise that can be tolerated to achieve high-fidelity transport. We also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.
Transport of spin qubits with donor chains under realistic experimental conditions
Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; Rahman, Rajib; Klimeck, Gerhard; Morello, Andrea
2016-07-25
The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO_{2} interface. We then estimate the required time scales and exchange couplings, and the level of noise that can be tolerated to achieve high-fidelity transport. As a result, we also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.
Transport of spin qubits with donor chains under realistic experimental conditions
Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; ...
2016-07-25
The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO2 interface. We then estimate the required time scales and exchange couplings, and the levelmore » of noise that can be tolerated to achieve high-fidelity transport. As a result, we also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.« less
Transport of spin qubits with donor chains under realistic experimental conditions
Mohiyaddin, Fahd A.; Kalra, Rachpon; Laucht, Arne; Rahman, Rajib; Klimeck, Gerhard; Morello, Andrea
2016-07-25
The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental nonidealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO_{2} interface. We then estimate the required time scales and exchange couplings, and the level of noise that can be tolerated to achieve high-fidelity transport. As a result, we also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.
NASA Astrophysics Data System (ADS)
Kishigi, Keita; Hasegawa, Yasumasa
2009-08-01
The successive transitions of the field-induced spin-density wave, which is labeled by the quantum number N of the Hall conductivity and the nesting vector, are known to depend on the shape of the quasi-one-dimensional Fermi surface. We study the condition for the appearance of the negative N states, where the quantized Hall conductivity changes the sign. We obtain the phase diagram for the negative N states in the parameter space of the higher harmonics in the Fermi surface ( tb' , t3 , and t4 ) to be stabilized with and without the periodic anion potential V in the perpendicular direction to the conducting axis, which are the cases in (TMTSF)2ClO4 and (TMTSF)2PF6 , respectively. The negative N phase is shown to be stabilized for the smaller values of t3 and t4 in the case of the finite V . Comparing with the experiment by Matsunaga [J. Phys. IV 131, 269 (2005)], where the quantum Hall effect is observed in (TMTSF)2ClO4 with various cooling rates, we obtain the parameter regions of t3 and t4 for (TMTSF)2ClO4 ( 0.06≲t3/tb'≲0.23 , 0≲t4/tb'≲0.08 , and V/tb'≲2.0 ).
NASA Astrophysics Data System (ADS)
Lisunov, K. G.; Wizent, N.; Waske, A.; Werner, J.; Tristan, N.; Sekar, C.; Krabbes, G.; Behr, G.; Arushanov, E.; Büchner, B.
2008-06-01
The resistivity ρ(T) of the spin-ladder compound CaCu2O3 measured along the Cu-O-Cu leg (j ∥b) exhibits a strongly activated character. It increases from ˜104 to ˜109 Ωm if T decreases from 350 to 100 K. The charge transfer above T ˜200 K is governed by a quasi-one-dimensional (1D) nearest-neighbor hopping (NNH) conductivity mechanism characterized by the law ρ(T )˜exp(Ea/kT). Below 200 K a novel quasi-1D variable-range hopping (VRH) conductivity law ρ(T )˜exp[(T0/T)3/4] is observed, predicted recently by Fogler, Teber, and Shklovskii [Phys. Rev. B 69, 035413 (2004)]. The NNH activation energy Ea and the VRH characteristic temperature T0 exhibit high sensitivity to the cation (Ca, Cu) content, decreasing by 2.3-2.5 times and by 3.0-3.2 times, respectively, when the composition of Ca is changed from 0.854 to 0.786-0.798 and the composition of Cu from 2.039 to 2.159-2.163. The behavior of Ea and T0 can be attributed to a corresponding variation of the concentration of intrinsic defects associated with Cu vacancies. On the other hand, no direct dependence of Ea and T0 to the excess oxygen concentration is observed.
The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains.
Fertitta, Edoardo; El Khatib, Muammar; Bendazzoli, Gian Luigi; Paulus, Beate; Evangelisti, Stefano; Leininger, Thierry
2015-12-28
The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection Sz has been derived.
The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains
Fertitta, Edoardo; Paulus, Beate; El Khatib, Muammar; Evangelisti, Stefano; Leininger, Thierry
2015-12-28
The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection S{sub z} has been derived.
The spin-partitioned total position-spread tensor: An application to Heisenberg spin chains
NASA Astrophysics Data System (ADS)
Fertitta, Edoardo; El Khatib, Muammar; Bendazzoli, Gian Luigi; Paulus, Beate; Evangelisti, Stefano; Leininger, Thierry
2015-12-01
The spin partition of the Total Position-Spread (TPS) tensor has been performed for one-dimensional Heisenberg chains with open boundary conditions. Both the cases of a ferromagnetic (high-spin) and an anti-ferromagnetic (low-spin) ground-state have been considered. In the case of a low-spin ground-state, the use of alternating magnetic couplings allowed to investigate the effect of spin-pairing. The behavior of the spin-partitioned TPS (SP-TPS) tensor as a function of the number of sites turned to be closely related to the presence of an energy gap between the ground-state and the first excited-state at the thermodynamic limit. Indeed, a gapped energy spectrum is associated to a linear growth of the SP-TPS tensor with the number of sites. On the other hand, in gapless situations, the spread presents a faster-than-linear growth, resulting in the divergence of its per-site value. Finally, for the case of a high-spin wave function, an analytical expression of the dependence of the SP-TPS on the number of sites n and the total spin-projection Sz has been derived.
Walter, Marie V; Cheval, Nicolas; Liszka, Olimpia; Malkoch, Michael; Fahmi, Amir
2012-04-10
The fabrication of well-defined one-dimensional (1D) arrays is becoming a challenge for the development of the next generation of advanced nanodevices. Herein, a simple concept is proposed for the in situ synthesis and self-assembly of gold nanoparticles (AuNPs) into 1D arrays via a one-step process. The results demonstrated the formation of nanoparticle chains (NPC) with high aspect ratio based on discrete Au nanoparticles stabilized by short thiol ligands. A model was proposed to explain the self-assembly based on the investigation of several parameters such as pH, solvent, temperature, and nature of the ligand on the 1D assembly formation. Hydrogen bonding was identified as a key factor to direct the self-assembly of the hybrid organic-inorganic nanomaterials into the well-defined 1D nanostructures. This simple and cost-effective concept could potentially be extended to the fabrication of a variety of hybrid 1D nanostructures possessing unique physical properties leading to a wide range of applications including catalysis, bionanotechnology, nanoelectronics, and photonics.
Random SU(2)-symmetric spin-S chains
NASA Astrophysics Data System (ADS)
Quito, V. L.; Hoyos, José A.; Miranda, E.
2016-08-01
We study the low-energy physics of a broad class of time-reversal invariant and SU(2)-symmetric one-dimensional spin-S systems in the presence of quenched disorder via a strong-disorder renormalization-group technique. We show that, in general, there is an antiferromagnetic phase with an emergent SU (2 S +1 ) symmetry. The ground state of this phase is a random singlet state in which the singlets are formed by pairs of spins. For integer spins, there is an additional antiferromagnetic phase which does not exhibit any emergent symmetry (except for S =1 ). The corresponding ground state is a random singlet one but the singlets are formed mostly by trios of spins. In each case the corresponding low-energy dynamics is activated, i.e., with a formally infinite dynamical exponent, and related to distinct infinite-randomness fixed points. The phase diagram has two other phases with ferromagnetic tendencies: a disordered ferromagnetic phase and a large spin phase in which the effective disorder is asymptotically finite. In the latter case, the dynamical scaling is governed by a conventional power law with a finite dynamical exponent.
Chaotic dynamics and spin correlation functions in a chain of nanomagnets
NASA Astrophysics Data System (ADS)
Chotorlishvili, L.; Toklikishvili, Z.; Komnik, A.; Berakdar, J.
2011-05-01
We study a chain of coupled nanomagnets in a classical approximation. We show that the infinitely long chain of coupled nanomagnets can be equivalently mapped onto an effective one-dimensional Hamiltonian with a fictitious time-dependent perturbation. We establish a connection between the dynamical characteristics of the classical system and spin correlation time. The decay rate for the spin correlation functions turns out to depend logarithmically on the maximal Lyapunov exponent. Furthermore, we discuss the nontrivial role of the exchange anisotropy within the chain.
Quasi-one-dimensional magnons in an intermetallic marcasite.
Stone, M B; Lumsden, M D; Nagler, S E; Singh, D J; He, J; Sales, B C; Mandrus, D
2012-04-20
We present inelastic neutron scattering measurements and first principles calculations examining the intermetallic marcasite CrSb(2). The observed spin-wave dispersion implies that the magnetic interactions are strongly one-dimensional with antiferromagnetic chains parallel to the crystalline c axis. Such low-dimensional excitations are unexpected in a semiconducting intermetallic system. Moreover, we observe a clear anisotropic thermal conductivity indicating that the magnetic anisotropy enhances thermoelectric properties along particular crystallographic directions.
Quasi-One-Dimensional Magnons in an Intermetallic Marcasite
NASA Astrophysics Data System (ADS)
Stone, M. B.; Lumsden, M. D.; Nagler, S. E.; Singh, D. J.; He, J.; Sales, B. C.; Mandrus, D.
2012-04-01
We present inelastic neutron scattering measurements and first principles calculations examining the intermetallic marcasite CrSb2. The observed spin-wave dispersion implies that the magnetic interactions are strongly one-dimensional with antiferromagnetic chains parallel to the crystalline c axis. Such low-dimensional excitations are unexpected in a semiconducting intermetallic system. Moreover, we observe a clear anisotropic thermal conductivity indicating that the magnetic anisotropy enhances thermoelectric properties along particular crystallographic directions.
Spin and Chiral Orderings of Frustrated Quantum Spin Chains
NASA Astrophysics Data System (ADS)
Kaburagi, Makoto; Kawamura, Hikaru; Hikihara, Toshiya
1999-10-01
The ordering offrustrated S=1/2 and 1 XY and Heisenberg spin chains with the competing nearest- and next-nearest-neighbor antiferromagneticcouplings is studied by the exact diagonalization and density-matrix renormalization-group methods. It is found that theS=1 XY chain exhibits both gapless and gapped `chiral' phases characterizedby the spontaneous breaking of parity, in which thelong-range order parameter is a chirality, κi=SixSi+1y-SiySi+1x, whereas the spin correlation decays either algebraically or exponentially. Such chiral phases are not realized in the S=1/2 XY chainor in the Heisenberg chains.
NASA Astrophysics Data System (ADS)
Hieida, Yasuhiro; Okunishi, Kouichi; Akutsu, Yasuhiro
1997-02-01
The product-wave-function renormalization group method, a new numerical renormalization group scheme proposed recently, is applied to one-dimensional quantum spin chains in a magnetic field. We find the zero-temperature magnetization curve of the spin chains, which excellently agrees with the exact solution in the whole range of the field.
Generating quantum states through spin chain dynamics
NASA Astrophysics Data System (ADS)
Kay, Alastair
2017-04-01
The spin chain is a theoretical work-horse of the physicist, providing a convenient, tractable model that yields insight into a host of physical phenomena including conduction, frustration, superconductivity, topological phases, localisation, phase transitions, quantum chaos and even string theory. Our ultimate aim, however, is not just to understand the properties of a physical system, but to harness it for our own ends. We therefore study the possibilities for engineering a special class of spin chain, envisaging the potential for this to feedback into the original physical systems. We pay particular attention to the generation of multipartite entangled states such as the W (Dicke) state, superposed over multiple sites of the chain.
Kerstein, A.R.
1996-12-31
One-Dimensional Turbulence is a new turbulence modeling strategy involving an unsteady simulation implemented in one spatial dimension. In one dimension, fine scale viscous and molecular-diffusive processes can be resolved affordably in simulations at high turbulence intensity. The mechanistic distinction between advective and molecular processes is thereby preserved, in contrast to turbulence models presently employed. A stochastic process consisting of mapping {open_quote}events{close_quote} applied to a one-dimensional velocity profile represents turbulent advection. The local event rate for given eddy size is proportional to the velocity difference across the eddy. These properties cause an imposed shear to induce an eddy cascade analogous in many respects to the eddy cascade in turbulent flow. Many scaling and fluctuation properties of self-preserving flows, and of passive scalars introduced into these flows, are reproduced.
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.
Ivanov, Dmitri A; Abanov, Alexander G
2013-02-01
We propose to describe correlations in classical and quantum systems in terms of full counting statistics of a suitably chosen discrete observable. The method is illustrated with two exactly solvable examples: the classical one-dimensional Ising model and the quantum spin-1/2 XY chain. For the one-dimensional Ising model, our method results in a phase diagram with two phases distinguishable by the long-distance behavior of the Jordan-Wigner strings. For the anisotropic spin-1/2 XY chain in a transverse magnetic field, we compute the full counting statistics of the magnetization and use it to classify quantum phases of the chain. The method, in this case, reproduces the previously known phase diagram. We also discuss the relation between our approach and the Lee-Yang theory of zeros of the partition function.
Finite size induces crossover temperature in growing spin chains
NASA Astrophysics Data System (ADS)
Sienkiewicz, Julian; Suchecki, Krzysztof; Hołyst, Janusz A.
2014-01-01
We introduce a growing one-dimensional quenched spin model that bases on asymmetrical one-side Ising interactions in the presence of external field. Numerical simulations and analytical calculations based on Markov chain theory show that when the external field is smaller than the exchange coupling constant J there is a nonmonotonous dependence of the mean magnetization on the temperature in a finite system. The crossover temperature Tc corresponding to the maximal magnetization decays with system size, approximately as the inverse of the Lambert W function. The observed phenomenon can be understood as an interplay between the thermal fluctuations and the presence of the first cluster determined by initial conditions. The effect exists also when spins are not quenched but fully thermalized after the attachment to the chain. By performing tests on real data we conceive the model is in part suitable for a qualitative description of online emotional discussions arranged in a chronological order, where a spin in every node conveys emotional valence of a subsequent post.
Finite size induces crossover temperature in growing spin chains.
Sienkiewicz, Julian; Suchecki, Krzysztof; Hołyst, Janusz A
2014-01-01
We introduce a growing one-dimensional quenched spin model that bases on asymmetrical one-side Ising interactions in the presence of external field. Numerical simulations and analytical calculations based on Markov chain theory show that when the external field is smaller than the exchange coupling constant J there is a nonmonotonous dependence of the mean magnetization on the temperature in a finite system. The crossover temperature Tc corresponding to the maximal magnetization decays with system size, approximately as the inverse of the Lambert W function. The observed phenomenon can be understood as an interplay between the thermal fluctuations and the presence of the first cluster determined by initial conditions. The effect exists also when spins are not quenched but fully thermalized after the attachment to the chain. By performing tests on real data we conceive the model is in part suitable for a qualitative description of online emotional discussions arranged in a chronological order, where a spin in every node conveys emotional valence of a subsequent post.
Integrable deformations of the XXZ spin chain
NASA Astrophysics Data System (ADS)
Beisert, Niklas; Fiévet, Lucas; de Leeuw, Marius; Loebbert, Florian
2013-09-01
We consider integrable deformations of the XXZ spin chain for periodic and open boundary conditions. In particular, we classify all long-range deformations and study their impact on the spectrum. As compared to the XXX case, we have the z-spin at our disposal, which induces two additional deformations: the short-range magnetic twist and a new long-range momentum-dependent twist.
NASA Astrophysics Data System (ADS)
Corona, L. A.; Salgado-García, R.
2016-12-01
In this paper we study a class of one-dimensional spin chain having a highly degenerated set of ground-state configurations. The model consists of spin chain having infinite-range pair interactions with a given structure. We show that the set of ground-state configurations of such a model can be fully characterized by means of symbolic dynamics. Particularly we found that the set ground-state configurations define what in symbolic dynamics is called sofic shift space. Finally we prove that this system has a non-vanishing residual entropy (the topological entropy of the shift space), which can be exactly calculated.
Topologically protected localised states in spin chains
Estarellas, Marta P.; D’Amico, Irene; Spiller, Timothy P.
2017-01-01
We consider spin chain families inspired by the Su, Schrieffer and Hegger (SSH) model. We demonstrate explicitly the topologically induced spatial localisation of quantum states in our systems. We present detailed investigations of the effects of random noise, showing that these topologically protected states are very robust against this type of perturbation. Systems with such topological robustness are clearly good candidates for quantum information tasks and we discuss some potential applications. Thus, we present interesting spin chain models which show promising applications for quantum devices. PMID:28225002
Topologically protected localised states in spin chains
NASA Astrophysics Data System (ADS)
Estarellas, Marta P.; D’Amico, Irene; Spiller, Timothy P.
2017-02-01
We consider spin chain families inspired by the Su, Schrieffer and Hegger (SSH) model. We demonstrate explicitly the topologically induced spatial localisation of quantum states in our systems. We present detailed investigations of the effects of random noise, showing that these topologically protected states are very robust against this type of perturbation. Systems with such topological robustness are clearly good candidates for quantum information tasks and we discuss some potential applications. Thus, we present interesting spin chain models which show promising applications for quantum devices.
Simulations of information transport in spin chains.
Cappellaro, P; Ramanathan, C; Cory, D G
2007-12-21
Transport of quantum information in linear spin chains has been the subject of much theoretical work. Experimental studies by NMR in solid state spin systems (a natural implementation of such models) is complicated since the dipolar Hamiltonian is not solely comprised of nearest-neighbor XY-Heisenberg couplings. We present here a similarity transformation between the XY Hamiltonian and the double-quantum Hamiltonian, an interaction which is achievable with the collective control provided by radio-frequency pulses. Not only can this second Hamiltonian simulate the information transport in a spin chain, but it also creates coherent states, whose intensities give an experimental signature of the transport. This scheme makes it possible to study experimentally the transport of polarization beyond exactly solvable models and explore the appearance of quantum coherence and interference effects.
Pair entanglement in dimerized spin-s chains
NASA Astrophysics Data System (ADS)
Boette, A.; Rossignoli, R.; Canosa, N.; Matera, J. M.
2016-12-01
We examine the pair entanglement in the ground state of finite dimerized spin-s chains interacting through anisotropic X Y couplings immersed in a transverse magnetic field by means of a self-consistent pair mean-field approximation. The approach, which makes no a priori assumptions on the pair states, predicts, for sufficiently low coupling between pairs, 2 s distinct dimerized phases for increasing fields below the pair factorizing field, separated by spin-parity-breaking phases. The dimerized phases lead to approximate magnetization and pair entanglement plateaus, while the parity-breaking phases are characterized by weak pair entanglement but non-negligible entanglement of the pair with the rest of the system. These predictions are confirmed by the exact results obtained in finite s =1 and s =3 /2 chains. It is also shown that for increasing values of the spin s , the entanglement of an isolated pair, as measured by the negativity, rapidly saturates in the anisotropic X Y case but increases as s1 /2 in the X X case, reflecting a distinct single-spin entanglement spectrum.
Entanglement negativity in random spin chains
NASA Astrophysics Data System (ADS)
Ruggiero, Paola; Alba, Vincenzo; Calabrese, Pasquale
2016-07-01
We investigate the logarithmic negativity in strongly disordered spin chains in the random-singlet phase. We focus on the spin-1/2 random Heisenberg chain and the random X X chain. We find that for two arbitrary intervals, the disorder-averaged negativity and the mutual information are proportional to the number of singlets shared between the two intervals. Using the strong-disorder renormalization group (SDRG), we prove that the negativity of two adjacent intervals grows logarithmically with the intervals' length. In particular, the scaling behavior is the same as in conformal field theory, but with a different prefactor. For two disjoint intervals the negativity is given by a universal simple function of the cross ratio, reflecting scale invariance. As a function of the distance of the two intervals, the negativity decays algebraically in contrast with the exponential behavior in clean models. We confirm our predictions using a numerical implementation of the SDRG method. Finally, we also implement density matrix renormalization group simulations for the negativity in open spin chains. The chains accessible in the presence of strong disorder are not sufficiently long to provide a reliable confirmation of the SDRG results.
Yang, Y. S.; Marsiglio, F.; Madsen, M.; Gaulin, Bruce D.; Rogge, R. B.; Fernandez-Baca, Jaime A
2002-01-01
Inelastic neutron-scattering profiles of spin waves in the dilute quasi-one-dimensional Ising-like antiferromagnet CsCo{sub 0.83}Mg{sub 0.17}Br{sub 3} have been investigated. Calculations of S{sup xx}(Q,{omega}), based on an effective spin Hamiltonian, accurately describe the experimental spin-wave spectrum of the 2J mode. The Q dependence of the energy of this spin-wave mode follows the analytical prediction {omega}{sub xx}(Q)=(2J)(1-5{var_epsilon}{sup 2}cos{sup 2}Qa+2{var_epsilon}{sup 2}){sup 1/2}, calculated by Ishimura and Shiba using perturbation theory.
Heisenberg antiferromagnetic chain with multiple spin 1/2 particles of different flavors per site
NASA Astrophysics Data System (ADS)
Duki, Solomon F.; Yu, Yi-Kuo
Motivated by the discoveries of quasi-1D magnetic systems, we studied a quantum mechanical spin lattice system consisting of a one-dimensional antiferromagnetic Heisenberg chain. In this system we considered M spin 1/2 particles of different flavors per site, and the low-lying states, ground state included, of the Hamiltonian was solved numerically using the exact diagonalization method for finite cluster sizes. We have also obtained the corresponding solutions for systems of the same chain length but with one spin M/2 particle per site. The low energy spectra of both systems are then compared. For M = 2 and M =3, our result shows that the two spin chain systems (one spin M/2 per site vs. M spin 1/2 of different flavors per site) have the same excitation spectra at low energy and the number of overlapped states increases as the size of the cluster increases. The observed overlap also indicates that low energy excitations of the M flavored spin 1/2 chain system selects the high spin states, effectively satisfying the Hund's Rule even though the system does not possess the orbital angular momentum. This work was supported by the Intramural Research Program of the National Library of Medicine at the National Institutes of Health.
Freezing distributed entanglement in spin chains
D'Amico, Irene; Lovett, Brendon W.; Spiller, Timothy P.
2007-09-15
We show how to freeze distributed entanglement that has been created from the natural dynamics of spin chain systems. The technique that we propose simply requires single-qubit operations and isolates the entanglement in specific qubits at the ends of branches. Such frozen entanglement provides a useful resource, for example for teleportation or distributed quantum processing. The scheme can be applied to a wide range of systems--including actual spin systems and alternative qubit embodiments in strings of quantum dots, molecules, or atoms.
Quantum criticality of hot random spin chains.
Vasseur, R; Potter, A C; Parameswaran, S A
2015-05-29
We study the infinite-temperature properties of an infinite sequence of random quantum spin chains using a real-space renormalization group approach, and demonstrate that they exhibit nonergodic behavior at strong disorder. The analysis is conveniently implemented in terms of SU(2)_{k} anyon chains that include the Ising and Potts chains as notable examples. Highly excited eigenstates of these systems exhibit properties usually associated with quantum critical ground states, leading us to dub them "quantum critical glasses." We argue that random-bond Heisenberg chains self-thermalize and that the excited-state entanglement crosses over from volume-law to logarithmic scaling at a length scale that diverges in the Heisenberg limit k→∞. The excited state fixed points are generically distinct from their ground state counterparts, and represent novel nonequilibrium critical phases of matter.
NASA Astrophysics Data System (ADS)
Montalenti, F.; Ferrando, R.
2000-11-01
We show that the recently proposed scaling laws [see G. Zhuang, W. Wang, Phys. Lett. A 268 (2000) 413] for chain diffusion on missing-row Pt(110) have no real meaning, since they cannot be extended outside the narrow chain-length range which has been considered by Zhuang and Wang. The only asymptotic scaling law gives a chain mobility which is inversely proportional to the chain length; however this asymptotic scaling behaviour is not physically important due to the occurrence of multiple upward promotions for long chains.
Quantum correlations between distant qubits conveyed by large-S spin chains
NASA Astrophysics Data System (ADS)
Nuzzi, Davide; Cuccoli, Alessandro; Vaia, Ruggero; Verrucchi, Paola
2017-08-01
We consider two distant spin-1/2 particles (or qubits) and a number of interacting objects, all with the same value S ≫1 of their respective spin, distributed on a one-dimensional lattice (or large-S spin chain). The quantum states of the chain are constructed by linearly combining tensor products of single-spin coherent states, whose evolution is determined accordingly, i.e., via classical-like equations of motions. We show that the quantum superposition of the above product states resulting from a local interaction between the first qubit and one spin of the chain evolves so that the second qubit, after having itself interacted with another spin of the chain, can be entangled with the first qubit. Obtaining such an outcome does not imply imposing constraints on the length of the chain or the distance between the qubits, which demonstrates the possibility of generating quantum correlations at a distance by means of a macroscopic system, as far as local interactions with just a few of its components are feasible.
Guided magnon transport in spin chains: Transport speed and correcting for disorder
NASA Astrophysics Data System (ADS)
Ahmed, Muhammad H.; Greentree, Andrew D.
2015-02-01
High-fidelity quantum information transport is necessary for most practical models of quantum computation. By analogy with optical waveguides, a spatiotemporally varying magnetic potential on a one-dimensional spin chain can achieve high-fidelity transport of spin excitations. By comparing different potential shapes, we establish the effects of potential shape on the fidelity and transport speed. We incorporate disorder into our model and show methods to minimize its effect on transport. Finally, we discuss implementations of our scheme in several accessible systems based on hydrogenic approximations.
One-Dimensionality and Whiteness
ERIC Educational Resources Information Center
Calderon, Dolores
2006-01-01
This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…
One-Dimensionality and Whiteness
ERIC Educational Resources Information Center
Calderon, Dolores
2006-01-01
This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…
Albia, Jason R.; Albao, Marvin A.
2015-03-15
Classical nucleation theory predicts that the evolution of mean island density with temperature during growth in one-dimensional systems obeys the Arrhenius relation. In this study, kinetic Monte Carlo simulations of a suitable atomistic lattice-gas model were performed to investigate the experimentally observed non-Arrhenius scaling behavior of island density in the case of one-dimensional Al islands grown on Si(100). Previously, it was proposed that adatom desorption resulted in a transition temperature signaling the departure from classical predictions. Here, the authors demonstrate that desorption above the transition temperature is not possible. Instead, the authors posit that the existence of a transition temperature is due to a combination of factors such as reversibility of island growth, presence of C-defects, adatom diffusion rates, as well as detachment rates at island ends. In addition, the authors show that the anomalous non-Arrhenius behavior vanishes when adatom binds irreversibly with C-defects as observed in In on Si(100) studies.
One-dimensional Quantum Fluids
NASA Astrophysics Data System (ADS)
Gervais, Guillaume
2015-03-01
Fifty year ago, Joachim Mazdak Luttinger generalized the Tomonaga theory of interactions in a one-dimensional metal and show that the prior restrictions imposed by Tomonaga were not necessary. This model is now known as the Tomonaga- Luttinger liquid model (TLL) and most remarkably it does have mathematically exact solutions. In the case of electrons, it predicts that the spin and charge sector should separate, with each of them propagating with their own velocities. While there has been many attempts (some with great success) to observe TLL behaviour in clean quantum wires designed on an ultra-clean semiconductor platform, overall the Luttinger physics is experimentally still in its infancy. For instance, little is known regarding the 1D physics in a strongly-interacting neutral system, whether from the point-of-view of TLL theory or even localization physics. Helium-4, the paradigm superfluid, and Helium-3, the paradigm Fermi liquid, should in principleboth become Luttinger liquids if taken to the one-dimensional limit. In the bosonic case, this is supported by large-scale Quantum Monte Carlo simulations which found that a lengthscale of ~ 2 nm is sufficient for the system to crossover to the 1D regime and display universal Luttinger scaling. At McGill University, an experiment has been constructed to measure the liquid helium mass flow through a single nanopore. The technique consists of drilling a single nanopore in a SiN membrane using a TEM, and then applying a pressure gradient across the membrane. Previously published data in 45nm diameter hole determined the superfluid critical velocity to be close to the limit set by the Feynman vortex rings model. More recent work performed on nanopores with radii as small as 3 nm (and a length of 30nm) show the critical exponent for superfluid velocity to significantly deviate from its bulk value, 2/3. This is an important hint for the crossing over to the one-dimensional state in a strongly-correlated bosonic liquid.
Thermodynamics of Inozemtsev's elliptic spin chain
NASA Astrophysics Data System (ADS)
Klabbers, Rob
2016-06-01
We study the thermodynamic behaviour of Inozemtsev's long-range elliptic spin chain using the Bethe ansatz equations describing the spectrum of the model in the infinite-length limit. We classify all solutions of these equations in that limit and argue which of these solutions determine the spectrum in the thermodynamic limit. Interestingly, some of the solutions are not selfconjugate, which puts the model in sharp contrast to one of the model's limiting cases, the Heisenberg XXX spin chain. Invoking the string hypothesis we derive the thermodynamic Bethe ansatz equations (TBA-equations) from which we determine the Helmholtz free energy in thermodynamic equilibrium and derive the associated Y-system. We corroborate our results by comparing numerical solutions of the TBA-equations to a direct computation of the free energy for the finite-length hamiltonian. In addition we confirm numerically the interesting conjecture put forward by Finkel and González-López that the original and supersymmetric versions of Inozemtsev's elliptic spin chain are equivalent in the thermodynamic limit.
Analytical and numerical studies of disordered spin-1 Heisenberg chains with aperiodic couplings
NASA Astrophysics Data System (ADS)
Casa Grande, H. L.; Laflorencie, N.; Alet, F.; Vieira, A. P.
2014-04-01
We investigate the low-temperature properties of the one-dimensional spin-1 Heisenberg model with geometric fluctuations induced by aperiodic but deterministic coupling distributions, involving two parameters. We focus on two aperiodic sequences, the Fibonacci sequence and the 6-3 sequence. Our goal is to understand how these geometric fluctuations modify the physics of the (gapped) Haldane phase, which corresponds to the ground state of the uniform spin-1 chain. We make use of different adaptations of the strong-disorder renormalization-group (SDRG) scheme of Ma, Dasgupta, and Hu, widely employed in the study of random spin chains, supplemented by quantum Monte Carlo and density-matrix renormalization-group numerical calculations, to study the nature of the ground state as the coupling modulation is increased. We find no phase transition for the Fibonacci chain, while we show that the 6-3 chain exhibits a phase transition to a gapless, aperiodicity-dominated phase similar to the one found for the aperiodic spin-1/2 XXZ chain. Contrary to what is verified for random spin-1 chains, we show that different adaptations of the SDRG scheme may lead to different qualitative conclusions about the nature of the ground state in the presence of aperiodic coupling modulations.
Martirosyan, A; Saakian, David B
2011-08-01
We apply the Hamilton-Jacobi equation (HJE) formalism to solve the dynamics of the chemical master equation (CME). We found exact analytical expressions (in large system-size limit) for the probability distribution, including explicit expression for the dynamics of variance of distribution. We also give the solution for some simple cases of the model with time-dependent rates. We derived the results of the Van Kampen method from the HJE approach using a special ansatz. Using the Van Kampen method, we give a system of ordinary differential equations (ODEs) to define the variance in a two-dimensional case. We performed numerics for the CME with stationary noise. We give analytical criteria for the disappearance of bistability in the case of stationary noise in one-dimensional CMEs.
Exact solution of the one-dimensional Hubbard model with arbitrary boundary magnetic fields
NASA Astrophysics Data System (ADS)
Li, Yuan-Yuan; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2014-02-01
The one-dimensional Hubbard model with arbitrary boundary magnetic fields is solved exactly via the Bethe ansatz methods. With the coordinate Bethe ansatz in the charge sector, the second eigenvalue problem associated with the spin sector is constructed. It is shown that the second eigenvalue problem can be transformed into that of the inhomogeneous XXX spin chain with arbitrary boundary fields which can be solved via the off-diagonal Bethe ansatz method.
Spin supersolid in an anisotropic spin-one Heisenberg chain.
Sengupta, P; Batista, C D
2007-11-23
We consider an S=1 Heisenberg chain with strong exchange (Delta=J(z)/J(perpendicular)) and single-ion uniaxial anisotropy (D) in a magnetic field (B) along the symmetry axis. The low-energy spectrum is described by an effective S=1/2 XXZ model that acts on two different low-energy sectors for a finite range of fields. The vacuum of each sector exhibits Ising-like antiferromagnetic ordering coexisting with the finite spin stiffness obtained from the exact solution of the XXZ model. In this way, we demonstrate the existence of a spin supersolid phase. We also compute the full Delta-B quantum phase diagram using a quantum Monte Carlo method.
NASA Astrophysics Data System (ADS)
Kozii, Vladyslav; Ruhman, Jonathan; Fu, Liang; Radzihovsky, Leo
2017-09-01
We study the quantum phase transition between a paramagnetic and ferromagnetic metal in the presence of Rashba spin-orbit coupling in one dimension. Using bosonization, we analyze the transition by means of renormalization group, controlled by an ɛ expansion around the upper critical dimension of two. We show that the presence of Rashba spin-orbit coupling allows for a new nonlinear term in the bosonized action, which generically leads to a fluctuation driven first-order transition. We further demonstrate that the Euclidean action of this system maps onto a classical smectic-A-C phase transition in a magnetic field in two dimensions. We show that the smectic transition is second order and is controlled by a new critical point.
NASA Astrophysics Data System (ADS)
Cheng, Jun-Qing; Wu, Wei; Xu, Jing-Bo
2017-09-01
We investigate the multipartite entanglement and trace distance of the one-dimensional anisotropic spin-1/2 XXZ spin chain with the Dzyaloshinskii-Moriya interaction and find that the Dzyaloshinskii-Moriya interaction can influence the entanglement distribution and increase the proportion of multipartite entanglement in the entanglement structure. Furthermore, we explore the quantum phase transition of the XXZ spin chain with Dzyaloshinskii-Moriya interaction by making use of the multipartite entanglement and trace distance along with the quantum renormalization group method. It is found that the first derivatives of renormalized multipartite entanglement and trace distance for the ground state have dramatic changes near the critical point, and the renormalized multipartite entanglement and trace distance obey the universal finite-size scaling laws in the vicinity of the quantum critical point.
Experimental Measurement of the Staggered Magnetization Curve for a Haldane Spin Chain
NASA Astrophysics Data System (ADS)
Zheludev, A.; Ressouche, E.; Maslov, S.; Yokoo, T.; Raymond, S.; Akimitsu, J.
1998-04-01
Long-range magnetic ordering in R2BaNiO5 ( R = magnetic rare earth) quasi-one-dimensional mixed-spin antiferromagnets is described by a simple mean-field model that is based on the intrinsic staggered magnetization function of isolated Haldane spin chains for the Ni subsystem, and single-ion magnetization functions for the rare earth ions. The model is applied to new experimental results obtained in powder diffraction experiments on Nd2BaNiO5 and NdYBaNiO5, and to previously published diffraction data for Er2BaNiO5. From this analysis we extract the bare staggered magnetization curve for Haldane spin chains in these compounds.
Spin analogs of superconductivity and integer quantum Hall effect in an array of spin chains
NASA Astrophysics Data System (ADS)
Hill, Daniel; Kim, Se Kwon; Tserkovnyak, Yaroslav
2017-05-01
Motivated by the successful idea of using weakly coupled quantum electronic wires to realize the quantum Hall effects and the quantum spin Hall effects, we theoretically study two systems composed of weakly coupled quantum spin chains within the mean-field approximations, which can exhibit spin analogs of superconductivity and the integer quantum Hall effect. First, a certain bilayer of two arrays of interacting spin chains is mapped, via the Jordan-Wigner transformation, to an attractive Hubbard model that exhibits fermionic superconductivity, which corresponds to spin superconductivity in the original spin Hamiltonian. Secondly, an array of spin-orbit-coupled spin chains in the presence of a suitable external magnetic field is transformed to an array of quantum wires that exhibits the integer quantum Hall effect, which translates into its spin analog in the spin Hamiltonian. The resultant spin superconductivity and spin integer quantum Hall effect can be characterized by their ability to transport spin without any resistance.
The molecular spin filter constructed from 1D organic chain
NASA Astrophysics Data System (ADS)
Chen, Wei; Xu, Ning; Wang, Baolin; Bian, Baoan
2014-06-01
We proposed a molecular spin filter, which is constructed from the 1D metallic organic chain (Fen+1(C6H4)n). The spin-polarized transport properties of the molecular spin filter are explored by combining density functional theory with nonequilibrium Green's function formalism. Theoretical results reveal that Fen+1(C6H4)n molecular chain exhibits robust spin filtering effect, and only the spin-down electrons can transmit through the molecular chain. At the given bias voltage window [-1 eV,1 eV], the calculated spin filter efficiency is close to 100% in the case of n≥3. We find that the effect of spin polarization origin from both Fen+1 and (C6H4)n. In addition, negative difference resistance behavior appears in Fen+1(C6H4)n molecular chain. The results can help us understand the spin transport properties of organic molecular chain.
NASA Astrophysics Data System (ADS)
Rajak, Atanu; Dutta, Amit
2014-04-01
We consider the temporal evolution of a zero-energy edge Majorana of a spinless p-wave superconducting chain following a sudden change of a parameter of the Hamiltonian. Starting from one of the topological phases that has an edge Majorana, the system is suddenly driven to the other topological phase or to the (topologically) trivial phases and to the quantum critical points (QCPs) separating these phases. The survival probability of the initial edge Majorana as a function of time is studied following the quench. Interestingly when the chain is quenched to the QCP, we find a nearly perfect oscillation of the survival probability, indicating that the Majorana travels back and forth between two ends, with a time period that scales with the system size. We also generalize to the situation when there is a next-nearest-neighbor hopping in a superconducting chain and there results in a pair of edge Majorana at each end of the chain in the topological phase. We show that the frequency of oscillation of the survival probability gets doubled in this case. We also perform an instantaneous quenching of the Hamiltonian (with two Majorana modes at each end of the chain) to an another Hamiltonian which has only one Majorana mode in equilibrium; the MSP shows oscillations as a function of time with a noticeable decay in the amplitude. On the other hand for a quenching which is reverse to the previous one, the MSP decays rapidly and stays close to zero with fluctuations in amplitude.
NASA Astrophysics Data System (ADS)
Kishigi, Keita; Hasegawa, Yasumasa
2007-06-01
We show that in (TMTSF)2ClO4 the field-induced spin-density wave (FISDW) with negative quantum number (N=-2) of the nesting vector is stabilized in some region in the parameters of magnetic field and the strength of the anion potential, which corresponds to the very recently observed phase diagram of (TMTSF)2ClO4 in the parameter plane of magnetic field vs cooling rate by Matsunaga [J. Phys. IV 131, 269 (2005)]. The spin-density wave is induced by the magnetic field in the quasi-one-dimensional conductors such as (TMTSF)2PF6 and (TMTSF)2ClO4 . The wave vector of the FISDW is quantized and the Hall conductivity is quantized corresponding to the quantum number (N) of the wave vector. In (TMTSF)2ClO4 , the ordering of the anion ClO4 makes the periodic potential, which has been known to drastically affect the FISDW. We study the instability to the FISDW by taking the eigenstates in the magnetic field numerically, with the periodic potential being treated nonperturbatively. We obtain the phase diagram of the quantum number N for FISDW in the quasi-one-dimensional systems in the parameter plane of magnetic field and the strength of the periodic potential, which can be controlled by the cooling rate.
Tsai, Hui-Lien; Yang, Chen-I; Wernsdorfer, Wolfgang; Huang, Siang-Hua; Jhan, Siang-Yu; Liu, Ming-Hsuan; Lee, Gene-Hsiang
2012-12-17
Two Mn(4) single-molecule-magnet (SMM)-based coordination polymers, {[Mn(4)O(salox)(3)(N(3))(3)(DMF)(2)(H(2)O)(dpp)]·0.5MeOH}(n) (1·0.5MeOH; H(2)salox = salicylaldoxime; dpp = 1,3-di-4-pyridylpropane; DMF = N,N-dimethylformamide) and {[Mn(4)O(Me-salox)(3)(N(3))(3)(dpp)(1.5)]·1.5Et(2)O}(n) (2·1.5Et(2)O; Me-H(2)salox = hydroxyphenylethanone oxime), are self-assembled from Mn(ClO(4))(2)·6H(2)O/H(2)salox and Mn(ClO(4))(2)·6H(2)O/Me-H(2)salox systems with dpp and NaN(3) in DMF/MeOH, respectively. Both compounds comprise a mixed-valence tetranuclear manganese core, [Mn(II)Mn(III)(3)O](9+), which serves as a building unit for subsequent assembly via oximate and azido ligands. The flexible dpp ligand links with a Mn(4) unit, leading to the formation of a one-dimensional helical structure in 1·0.5MeOH and a three-dimensional pcu network in 2·1.5Et(2)O. The magnetic data analysis shows that antiferromagnetic interactions within the Mn(4) units resulted in S = (3)/(2) and (7)/(2) ground states for 1·0.5MeOH and 2·1.5Et(2)O, respectively. Both compounds show SMM behavior, as evidenced by frequency-dependent out-of-phase signals in alternating-current magnetic susceptibility and magnetic hysteresis loop studies with an energy barrier of U(eff) = 37 K for 2·1.5Et(2)O.
K2Ca4[(UO2)(Si2O7)2]: A Uranyl Silicate with a One-Dimensional Chain Structure.
Liu, Chia-Lin; Liu, Hsin-Kuan; Chang, Wen-Jung; Lii, Kwang-Hwa
2015-09-08
A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, β = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K(+) and Ca(2+) cations. It is the first example of uranyl silicate with a 1D chain structure.
NASA Astrophysics Data System (ADS)
Derrida, Bernard; Hakim, Vincent; Pasquier, Vincent
1996-12-01
For the zero-temperature Glauber dynamics of the q-state Potts model, the fraction r(q, t) of spins which never flip up to time t decays like a power law r(q, t)˜t -θ(q) when the initial condition is random. By mapping the problem onto an exactly soluble one-species coagulation model ( A+A→A) or alternatively by transforming the problem into a free-fermion model, we obtain the exact expression of θ( q) for all values of q. The exponent π( q) is in general irrational, θ(3)=0.53795082..., θ(4)=0.63151575..., ..., with the exception of q=2 and q=∞, for which θ(2)=3/8 and θ(∞)=1.
One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4
Disseler, S. M.; Chen, Y.; Yeo, S.; Gasparovic, G.; Piccoli, P. M. B.; Schultz, A. J.; Qiu, Y.; Huang, Q.; Cheong, S.-W.; Ratcliff, W.
2015-01-01
We report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ions on the spinel lattice. PMID:26644220
One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4
Disseler, S. M.; Chen, Y.; Yeo, S.; ...
2015-12-08
In this paper we report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn2O4. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn3+ ionsmore » on the spinel lattice.« less
One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn_{2}O_{4}
Disseler, S. M.; Chen, Y.; Yeo, S.; Gasparovic, G.; Piccoli, P. M. B.; Schultz, A. J.; Qiu, Y.; Huang, Q.; Cheong, S. -W.; Ratcliff, W.
2015-12-08
In this paper we report on the intriguing evolution of the dynamical spin correlations of the frustrated spinel ZnMn_{2}O_{4}. Inelastic neutron scattering and magnetization studies reveal that the dynamical correlations at high temperatures are 1D. At lower temperature, these dynamical correlations become 2D. Surprisingly, the dynamical correlations condense into a quasi 2D Ising-like ordered state, making this a rare observation of two dimensional order on the spinel lattice. Remarkably, 3D ordering is not observed down to temperatures as low as 300 mK. This unprecedented dimensional crossover stems from frustrated exchange couplings due to the huge Jahn-Teller distortions around Mn^{3+} ions on the spinel lattice.
Coltrin, M.E. ); Kee, R.J.; Evans, G.H.; Meeks, E.; Rupley, F.M.; Grcar, J.F. )
1991-08-01
In rotating-disk reactor a heated substrate spins (at typical speeds of 1000 rpm or more) in an enclosure through which the reactants flow. The rotating disk geometry has the important property that in certain operating regimes{sup 1} the species and temperature gradients normal to the disk are equal everywhere on the disk. Thus, such a configuration has great potential for highly uniform chemical vapor deposition (CVD),{sup 2--5} and indeed commercial rotating-disk CVD reactors are now available. In certain operating regimes, the equations describing the complex three-dimensional spiral fluid motion can be solved by a separation-of-variables transformation{sup 5,6} that reduces the equations to a system of ordinary differential equations. Strictly speaking, the transformation is only valid for an unconfined infinite-radius disk and buoyancy-free flow. Furthermore, only some boundary conditions are consistent with the transformation (e.g., temperature, gas-phase composition, and approach velocity all specified to be independent of radius at some distances above the disk). Fortunately, however, the transformed equations will provide a very good practical approximation to the flow in a finite-radius reactor over a large fraction of the disk (up to {approximately}90% of the disk radius) when the reactor operating parameters are properly chosen, i.e, high rotation rates. In the limit of zero rotation rate, the rotating disk flow reduces to a stagnation-point flow, for which a similar separation-of-variables transformation is also available. Such flow configurations ( pedestal reactors'') also find use in CVD reactors. In this report we describe a model formulation and mathematical analysis of rotating-disk and stagnation-point CVD reactors. Then we apply the analysis to a compute code called SPIN and describe its implementation and use. 31 refs., 4 figs.
Work fluctuations in quantum spin chains.
Dorosz, Sven; Platini, Thierry; Karevski, Dragi
2008-05-01
We study the work fluctuations of two types of finite quantum spin chains under the application of a time-dependent magnetic field in the context of the fluctuation relation and Jarzynski equality. The two types of quantum chains correspond to the integrable Ising quantum chain and the nonintegrable XX quantum chain in a longitudinal magnetic field. For several magnetic field protocols, the quantum Crooks and Jarzynski relations are numerically tested and fulfilled. As a more interesting situation, we consider the forcing regime where a periodic magnetic field is applied. In the Ising case we give an exact solution in terms of double-confluent Heun functions. We show that the fluctuations of the work performed by the external periodic drift are maximum at a frequency proportional to the amplitude of the field. In the nonintegrable case, we show that depending on the field frequency a sharp transition is observed between a Poisson-limit work distribution at high frequencies toward a normal work distribution at low frequencies.
Frustrated magnetism in the spin-chain metal Yb2Fe12P7
NASA Astrophysics Data System (ADS)
Baumbach, R. E.; Hamlin, J. J.; Janoschek, M.; Singleton, J.; Maple, M. B.
2016-02-01
Magnetization measurements for magnetic fields {μ0}H up to 60 T are reported for the noncentrosymmetric spin-chain metal Yb2Fe12P7. These measurements reveal behavior that is consistent with Ising-like spin chain magnetism that produces pronounced spin degeneracy. In particular, we find that although a Brillouin field dependence is observed in M(H) for H\\bot ~c with a saturation moment that is close to the expected value for free ions of Yb3+ , non-Brillouin-like behavior is seen for H~\\parallel ~c with an initial saturation moment that is nearly half the free ion value. In addition, hysteretic behavior that extends above the ordering temperature {{T}\\text{M}} is seen for H~\\parallel ~c but not for H~\\bot ~c , suggesting out-of-equilibrium physics. This point of view is strengthened by the observation of a spin reconfiguration in the ordered state for H~\\parallel ~c which is only seen for T≤slant {{T}\\text{M}} and after polarizing the spins. Together with the heat capacity data, these results suggest that the anomalous low temperature phenomena that were previously reported (Baumbach 2010 et al Phys. Rev. Lett. 105 106403) are driven by spin degeneracy that is related to the Ising-like one dimensional chain-like configuration of the Yb ions.
Papaemmanouil, Christina; Tsiafoulis, Constantinos G; Alivertis, Dimitrios; Tzamaloukas, Ouranios; Miltiadou, Despoina; Tzakos, Andreas G; Gerothanassis, Ioannis P
2015-06-10
We report a rapid, direct, and unequivocal spin-chromatographic separation and identification of minor components in the lipid fraction of milk and common dairy products with the use of selective one-dimensional (1D) total correlation spectroscopy (TOCSY) nuclear magnetic resonance (NMR) experiments. The method allows for the complete backbone spin-coupling network to be elucidated even in strongly overlapped regions and in the presence of major components from 4 × 10(2) to 3 × 10(3) stronger NMR signal intensities. The proposed spin-chromatography method does not require any derivatization steps for the lipid fraction, is selective with excellent resolution, is sensitive with quantitation capability, and compares favorably to two-dimensional (2D) TOCSY and gas chromatography-mass spectrometry (GC-MS) methods of analysis. The results of the present study demonstrated that the 1D TOCSY NMR spin-chromatography method can become a procedure of primary interest in food analysis and generally in complex mixture analysis.
Charge diffusion in the one-dimensional Hubbard model
NASA Astrophysics Data System (ADS)
Steinigeweg, R.; Jin, F.; De Raedt, H.; Michielsen, K.; Gemmer, J.
2017-08-01
We study the real-time and real-space dynamics of charge in the one-dimensional Hubbard model in the limit of high temperatures. To this end, we prepare pure initial states with sharply peaked density profiles and calculate the time evolution of these nonequilibrium states, by using numerical forward-propagation approaches to chains as long as 20 sites. For a class of typical states, we find excellent agreement with linear-response theory and unveil the existence of remarkably clean charge diffusion in the regime of strong particle-particle interactions. We additionally demonstrate that, in the half-filling sector, this diffusive behavior does not depend on certain details of our initial conditions, i.e., it occurs for five different realizations with random and nonrandom internal degrees of freedom, single and double occupation of the central site, and displacement of spin-up and spin-down particles.
On the particle excitations in the XXZ spin chain
NASA Astrophysics Data System (ADS)
Ovchinnikov, A. A.
2013-12-01
We continue to study the excited states for the XXZ spin chain corresponding to the complex roots of the Bethe Ansatz equations with the imaginary part equal to π/2. We propose the particle-hole symmetry which relates the eigenstates build up from the two different pseudovacuum states. We find the XXX spin chain limit for the eigenstates with the complex roots. We also comment on the low-energy excited states for the XXZ spin chain.
Baril-Robert, François; Li, Xiaobo; Katz, Michael J; Geisheimer, Andrew R; Leznoff, Daniel B; Patterson, Howard
2011-01-03
A series of d(10) dicyanometallate polymeric compounds were studied by electronic spectroscopy and density functional theory (DFT) calculations. In these materials, the negatively charged one-dimensional (1D) polymeric chains are linked together by [M(en)(2)](2+) (M = Cu(II) and Zn(II); en = ethylenediamine). More than innocent building blocks, the [M(en)(2)](2+) units offer a possible synthetic way to modify electronic properties of the materials. Through its low energy d-d excited state, the d(9) copper(II) ions offer deactivation pathways for the normally emissive dicyanometallate polymer. Deactivation was shown to be specific to the excited state energy.
Antiferromagnetic S=1/2 Spin Chain Driven by p-Orbital Ordering in CsO2
NASA Astrophysics Data System (ADS)
Riyadi, Syarif; Zhang, Baomin; de Groot, Robert A.; Caretta, Antonio; van Loosdrecht, Paul H. M.; Palstra, Thomas T. M.; Blake, Graeme R.
2012-05-01
We demonstrate, using a combination of experiment and density functional theory, that orbital ordering drives the formation of a one-dimensional (1D) S=1/2 antiferromagnetic spin chain in the 3D rocksalt structure of cesium superoxide (CsO2). The magnetic superoxide anion (O2-) exhibits degeneracy of its 2p-derived molecular orbitals, which is lifted by a structural distortion on cooling. A spin chain is then formed by zigzag ordering of the half-filled superoxide orbitals, promoting a superexchange pathway mediated by the pz orbitals of Cs+ along only one crystal direction. This scenario is analogous to the 3d-orbital-driven spin chain found in the perovskite KCuF3 and is the first example of an inorganic quantum spin system with unpaired p electrons.
Low-energy excitations of the semimetallic one-dimensional S=1/2 antiferromagnet Yb 4As 3
NASA Astrophysics Data System (ADS)
Schmidt, B.; Aoki, H.; Cichorek, T.; Custers, J.; Gegenwart, P.; Kohgi, M.; Lang, M.; Langhammer, C.; Ochiai, A.; Paschen, S.; Steglich, F.; Suzuki, T.; Thalmeier, P.; Wand, B.; Yaresko, A.
2001-07-01
We investigate a new route to quasi-one-dimensional spin-chain systems which originates from the charge-ordering transition out of a homogeneous mixed-valence state. We present evidence that Yb 4As 3 and P, Sb doped mixed crystals are well described by this mechanism. Many thermodynamic and low-temperature transport heavy-fermion-like properties can be explained by the existence of low-lying quasi-one-dimensional spin excitations in the Yb 3+-chains. The observation of soliton excitations in a transverse external field gives further support to the existence of spin chains in Yb 4As 3. We also present recent results on spin-glass behavior at very low temperature caused by the interchain coupling and disorder. In addition, the yet unexplained magnetotransport effects are discussed.
Non-Abelian topological spin liquids from arrays of quantum wires or spin chains
NASA Astrophysics Data System (ADS)
Huang, Po-Hao; Chen, Jyong-Hao; Gomes, Pedro R. S.; Neupert, Titus; Chamon, Claudio; Mudry, Christopher
2016-05-01
We construct two-dimensional non-Abelian topologically ordered states by strongly coupling arrays of one-dimensional quantum wires via interactions. In our scheme, all charge degrees of freedom are gapped, so the construction can use either quantum wires or quantum spin chains as building blocks, with the same end result. The construction gaps the degrees of freedom in the bulk, while leaving decoupled states at the edges that are described by conformal field theories (CFT) in (1 +1 ) -dimensional space and time. We consider both the cases where time-reversal symmetry (TRS) is present or absent. When TRS is absent, the edge states are chiral and stable. We prescribe, in particular, how to arrive at all the edge states described by the unitary CFT minimal models with central charges c <1 . These non-Abelian spin liquid states have vanishing quantum Hall conductivities, but nonzero thermal ones. When TRS is present, we describe scenarios where the bulk state can be a non-Abelian, nonchiral, and gapped quantum spin liquid, or a gapless one. In the former case, we find that the edge states are also gapped. The paper provides a brief review of non-Abelian bosonization and affine current algebras, with the purpose of being self-contained. To illustrate the methods in a warm-up exercise, we recover the tenfold way classification of two-dimensional noninteracting topological insulators using the Majorana representation that naturally arises within non-Abelian bosonization. Within this scheme, the classification reduces to counting the number of null singular values of a mass matrix, with gapless edge modes present when left and right null eigenvectors exist.
NASA Astrophysics Data System (ADS)
Nandy, Atanu; Pal, Biplab; Chakrabarti, Arunava
2016-08-01
It is shown that an entire class of off-diagonally disordered linear lattices composed of two basic building blocks and described within a tight-binding model can be tailored to generate absolutely continuous energy bands. It can be achieved if linear atomic clusters of an appropriate size are side-coupled to a suitable subset of sites in the backbone, and if the nearest-neighbor hopping integrals, in the backbone and in the side-coupled cluster, bear a certain ratio. We work out the precise relationship between the number of atoms in one of the building blocks in the backbone and that in the side attachment. In addition, we also evaluate the definite correlation between the numerical values of the hopping integrals at different subsections of the chain, that can convert an otherwise point spectrum (or a singular continuous one for deterministically disordered lattices) with exponentially (or power law) localized eigenfunctions to an absolutely continuous spectrum comprising one or more bands (subbands) populated by extended, totally transparent eigenstates. The results, which are analytically exact, put forward a non-trivial variation of the Anderson localization (Anderson P. W., Phys. Rev., 109 (1958) 1492), pointing towards its unusual sensitivity to the numerical values of the system parameters and, go well beyond the other related models such as the Random Dimer Model (RDM) (Dunlap D. H. et al., Phys. Rev. Lett., 65 (1990) 88).
NASA Astrophysics Data System (ADS)
Kondo, Takeshi; Khasanov, R.; Karpinski, J.; Kazakov, S. M.; Zhigadlo, N. D.; Bukowski, Z.; Shi, M.; Bendounan, A.; Sassa, Y.; Chang, J.; Pailhés, S.; Mesot, J.; Schmalian, J.; Keller, H.; Kaminski, A.
2010-12-01
We have investigated the electronic states in quasi-one-dimensional CuO chains by microprobe angle resolved photoemission spectroscopy. We find that the quasiparticle Fermi surface consists of six disconnected segments, consistent with recent theoretical calculations that predict the formation of narrow, elongated Fermi surface pockets for coupled CuO chains. In addition, we find a strong renormalization effect with a significant kink structure in the band dispersion. The properties of this latter effect [energy scale (˜40meV), temperature dependence, and behavior with Zn-doping] are identical to those of the bosonic mode observed in CuO2 planes of high-temperature superconductors, indicating they have a common origin.
Li, Yan; Yu, Jia-Wen; Liu, Zhong-Yi; Yang, En-Cui; Zhao, Xiao-Jun
2015-01-05
Three new homometallic lanthanide complexes with mixed carboxylate-modified rigid ligands, [Ln(μ3-OH)(na)(pyzc)]n (na(-) = 1-naphtholate, pyzc(-) = 2-pyrazinecarboxylate, Ln = Dy (1), Yb (2), and Gd (3)), were solvothermally synthesized, and their structures and magnetic as well as photophysical properties were completely investigated. Complexes 1-3 are crystallographically isostructural, exhibiting linear chains with four bidentate bridging μ-COO(-) moieties encapsulated cubic {Ln4(μ3-OH)4}(8+) clusters repeatedly extended by 4-fold chelating-bridging-pyzc(-) connectors. Magnetically, the former two complexes with highly anisotropic Dy(III) and weak anisotropic Yb(III) ions in the distorted NO7 triangular dodecahedron coordination environment display field-induced slow relaxation of magnetization. Fitting the dynamic magnetic data to the Arrhenius law gives energy barrier ΔE/kB = 39.6 K and pre-exponential factor τo = 1.52 × 10(-8) s for 1 and ΔE/kB = 14.1 K and τo = 2.13 × 10(-7) s for 2. By contrast, complex 3 with isotropic Gd(III) ion and weak intracluster antiferromagnetic coupling shows a significant cryogenic magnetocaloric effect, with a maximum -ΔSm value of 30.0 J kg(-1) K(-1) at 2.5 K and 70 kOe. Additionally, the chromophoric na(-) and pyzc(-) ligands can serve as antenna groups, selectively sensitizing the Dy(III)- and Yb(III)-based luminescence of 1 and 2 in the UV-visible region by an intramolecular energy transfer process. Thus, complexes 1-3, incorporating field-induced slow magnetic magnetization and interesting luminescence together, can be used as composite magneto-optical materials. More importantly, these interesting results further demonstrate that the mixed-ligand system with rigid carboxylate-functionalized chromophores can be excellent candidates for the preparations of new bifunctional magneto-optical materials.
Brozik, J.A.; Scott, B.L.; Swanson, B.I.
1999-12-02
The unique linear chain compound [Pt(en){sub 2}I{sub 2}][Pt(CN){sub 4}] {l{underscore}brace}where en = ethylenediamine{r{underscore}brace} has been synthesized through a standard method. The results of a structural analysis by X-ray crystallography reveal this new MX compound to be quasi-one-dimensional with complete chain-to-chain registry to give a completely ordered structure. The results of resonance Raman, IR, diffuse reflectance, and X-ray crystallography reveal that the Pt centers are highly charge disproportionated with a large commensurate distortion of the iodide sublattice about the Pt center of higher charge. These results reveal that this material is the strongest CDW MX compound, containing iodide bridges, reported to date. Resonance Raman experiments have shown that five A{sub g} (C{sub 2h} site symmetry) Raman bands are strongly enhanced. These correspond to three in-chain Pt-I modes and two (chain perpendicular) CN stretches and are interpreted in terms of strong phonon coupling to the IVCT band.
Universal quantum computation with ordered spin-chain networks
Tserkovnyak, Yaroslav; Loss, Daniel
2011-09-15
It is shown that anisotropic spin chains with gapped bulk excitations and magnetically ordered ground states offer a promising platform for quantum computation, which bridges the conventional single-spin-based qubit concept with recently developed topological Majorana-based proposals. We show how to realize the single-qubit Hadamard, phase, and {pi}/8 gates as well as the two-qubit controlled-not (cnot) gate, which together form a fault-tolerant universal set of quantum gates. The gates are implemented by judiciously controlling Ising exchange and magnetic fields along a network of spin chains, with each individual qubit furnished by a spin-chain segment. A subset of single-qubit operations is geometric in nature, relying on control of anisotropy of spin interactions rather than their strength. We contrast topological aspects of the anisotropic spin-chain networks to those of p-wave superconducting wires discussed in the literature.
Sine-square deformation of solvable spin chains and conformal field theories
NASA Astrophysics Data System (ADS)
Katsura, Hosho
2012-03-01
We study solvable spin chains, one-dimensional massless Dirac fermions and conformal field theories (CFTs) with sine-square deformation (SSD), in which the Hamiltonian density is modulated by the function f(x) = sin 2(πx/ℓ), where x is the position and ℓ is the length of the system. For the XY chain and the transverse field Ising chain at criticality, it is shown that the ground state of an open system with SSD is identical to that of a uniform chain with periodic boundary conditions. The same holds for the massless Dirac fermions with SSD, corresponding to the continuum limit of the gapless XY chain. For general CFTs, we find that the Hamiltonian of a system with SSD has an expression in terms of the generators of the Virasoro algebra. This allows us to show that the vacuum state is an exact eigenstate of the sine-square deformed Hamiltonian. Furthermore, for a restricted class of CFTs associated with affine Lie (Kac-Moody) algebras, including c = 1 Gaussian CFT, we prove that the vacuum is an exact ground state of the deformed Hamiltonian. This explains why the SSD has succeeded in suppressing boundary effects in one-dimensional critical systems, as observed in previous numerical studies.
Hermes, Matthew R.; Hirata, So
2015-09-14
One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree–Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree–Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard–Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga–Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.
Hermes, Matthew R; Hirata, So
2015-09-14
One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.
NASA Astrophysics Data System (ADS)
Hermes, Matthew R.; Hirata, So
2015-09-01
One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.
De, Santanu Kumar, Kranti; Banerjee, A.; Chaddah, P.
2016-05-23
We have found that the geometrically frustrated spin chain compound Ca{sub 3}Co{sub 2}O{sub 6} belonging to Ising like universality class with uniaxial anisotropy shows kinetic arrest of first order intermediate phase (IP) to ferrimagnetic (FIM) transition. In this system, dc magnetization measurements followed by different protocols suggest the coexistence of high temperature IP with equilibrium FIM phase in low temperature. Formation of metastable state due to hindered first order transition has also been probed through cooling and heating in unequal field (CHUF) protocol. Kinetically arrested high temperature IP appears to persist down to almost the spin freezing temperature in this system.
On the Relationship Between Sigma Models and Spin Chains
NASA Astrophysics Data System (ADS)
Controzzi, D.; Hawkins, E.
We consider the two-dimensional O(3) non-linear sigma model with topological term using a lattice regularization introduced by Shankar and Read [Nucl. Phys. B 336, 457 (1990)], that is suitable for studying the strong coupling regime. When this lattice model is quantized, the coefficient θ of the topological term is quantized as θ=2πs, with s integer or half-integer. We study in detail the relationship between the low energy behaviour of this theory and the one-dimensional spin-s Heisenberg model. We generalize the analysis to sigma models with other symmetries.
Frustration-induced quantum phases in mixed spin chain with frustrated side chains
NASA Astrophysics Data System (ADS)
Hida, Kazuo; Takano, Ken'Ichi
2008-08-01
A mixed Heisenberg spin chain with frustrated side chains is investigated by numerical and perturbational calculations. A frustration-induced quantum partially polarized ferrimagnetic phase and a nonmagnetic spin quadrupolar phase are found adjacent to the conventional Lieb-Mattis-type ferrimagnetic phase or the nonmagnetic singlet cluster solid phases. The partially polarized ferrimagnetic phase has an incommensurate spin structure. Similar structures are commonly found in other frustration-induced partially polarized ferrimagnetic phases. Numerical results also suggest a series of almost critical nonmagnetic ground states in a highly frustrated regime if the side chain spins weakly couple to the main chain.
Non-Markovian dynamics in the extended cluster spin-1/2 XX chain
NASA Astrophysics Data System (ADS)
Mahmoudi, M.; Mahdavifar, S.; Zadeh, T. Mohammad Ali; Soltani, M. R.
2017-01-01
We study the dynamics of entanglement, mutual information, and quantum discord in the extended cluster spin-1/2 XX chain, equivalent to a one-dimensional spin-1/2 XX model with three-spin interaction (TSI). Selecting the nearest neighbor pair spins as an open quantum system, the rest of the chain plays the role of the environment. The two-point Heisenberg and the TSI are responsible for coupling between the system and the environment. Although the revival phenomenon of quantum correlations as an indication of non-Markovian dynamics is observed for TSI stronger than the Heisenberg interaction, the study of the trace distance has proven that the dynamical phase transition from the Markovian to the non-Markovian regime happens at a critical value where the TSI is equal to half of the Heisenberg interaction. By focusing on the nearest neighbor pair spins of the environment, we have also shown that the dynamics of quantum correlation in the environment is sensitive to Markovian and non-Markovian regions.
Quantum phase transition in dimerised spin-1/2 chains
NASA Astrophysics Data System (ADS)
Das, Aparajita; Bhadra, Sreeparna; Saha, Sonali
2015-11-01
Quantum phase transition in dimerised antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical (or critical like) points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs too in the same dimer chain. Though closed dimerised isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied.
Spin Helicity in Chiral Lanthanide Chains.
Mihalcea, Ionut; Perfetti, Mauro; Pineider, Francesco; Tesi, Lorenzo; Mereacre, Valeriu; Wilhelm, Fabrice; Rogalev, Andrei; Anson, Christopher E; Powell, Annie K; Sessoli, Roberta
2016-10-17
We report here the determination of the helical spin structure of three Ln-based chiral chains of the formula [Ln(Hnic)(nic)2(NO3)]n (Hnic = nicotinic acid; Ln = Tb, Dy, and Er) by means of cantilever torque magnetometry. While the Dy and Er derivatives are strongly axial (easy-axis and easy-plane anisotropy, respectively), the Tb derivative is characterized by a remarkable rhombicity. In agreement with these findings, alternating-current susceptibility reveals slow magnetic relaxation only in the Dy derivative. Dilution of Dy(III) ions in the diamagnetic Y-based analogue shows that the weak ferromagnetic intrachain interactions do not contribute significantly to the energy barrier for the reversal of magnetization, which is better described as a single-ion process. Single crystals of the two enantiomers of the Dy derivative have also been investigated using hard X-ray synchrotron radiation at the L-edge of the metal revealing optical activity although with negligible involvement of the 4f electrons of the Dy(III) ion.
Charge and Spin Dynamics of the Hubbard Chains
NASA Technical Reports Server (NTRS)
Park, Youngho; Liang, Shoudan
1999-01-01
We calculate the local correlation functions of charge and spin for the one-chain and two-chain Hubbard model using density matrix renormalization group method and the recursion technique. Keeping only finite number of states we get good accuracy for the low energy excitations. We study the charge and spin gaps, bandwidths and weights of the spectra for various values of the on-site Coulomb interaction U and the electron filling. In the low energy part, the local correlation functions are different for the charge and spin. The bandwidths are proportional to t for the charge and J for the spin respectively.
Sublattice entanglement and quantum phase transitions in antiferromagnetic spin chains
NASA Astrophysics Data System (ADS)
Chen, Yan; Zanardi, Paolo; Wang, Z. D.; Zhang, F. C.
2006-06-01
Entanglement of the ground states in the S = 1/2 XXZ chain, dimerized Heisenberg spin chain, two-leg spin ladders as well as S = 1 anisotropic Haldane chain is analysed using the entanglement entropy between a selected sublattice of spins and the rest of the system. In particular, we reveal that quantum phase transition points/boundaries may be identified based on the analysis on the local extreme of this sublattice entanglement entropy, which is illustrated to be superior over the concurrence scenario and may enable us to explore quantum phase transitions in many other systems including higher dimensional ones.
Knitting distributed cluster-state ladders with spin chains
Ronke, R.; D'Amico, I.; Spiller, T. P.
2011-09-15
Recently there has been much study on the application of spin chains to quantum state transfer and communication. Here we discuss the utilization of spin chains (set up for perfect quantum state transfer) for the knitting of distributed cluster-state structures, between spin qubits repeatedly injected and extracted at the ends of the chain. The cluster states emerge from the natural evolution of the system across different excitation number sectors. We discuss the decohering effects of errors in the injection and extraction process as well as the effects of fabrication and random errors.
ac Magnetization transport and power absorption in nonitinerant spin chains.
Trauzettel, Björn; Simon, Pascal; Loss, Daniel
2008-07-04
We investigate the ac transport of magnetization in nonitinerant quantum systems such as spin chains described by the XXZ Hamiltonian. Using linear response theory, we calculate the ac magnetization current and the power absorption of such magnetic systems. Remarkably, the difference in the exchange interaction of the spin chain itself and the bulk magnets (i.e., the magnetization reservoirs), to which the spin chain is coupled, strongly influences the absorbed power of the system. This feature can be used in future spintronic devices to control power dissipation. Our analysis allows us to make quantitative predictions about the power absorption, and we show that magnetic systems are superior to their electronic counterparts.
Thermodynamics of a spin-1/2 XYZ Heisenberg chain with a Dzyaloshinskii-Moriya interaction
NASA Astrophysics Data System (ADS)
Xi, Bin; Hu, Shijie; Luo, Qiang; Zhao, Jize; Wang, Xiaoqun
2017-01-01
We study the thermodynamics of a spin-1/2 XYZ Heisenberg chain with a Dzyaloshinskii-Moriya interaction. This model describes the low-energy behaviors of a one-dimensional two-component bosonic model with a synthetic spin-orbit coupling in the deep insulating region. In the limit U'/U →∞ , where U is the strength of the onsite intracomponent repulsion and U' is the intercomponent one, we solve our model exactly by Jordan-Wigner transformation, and thus provide a benchmark for our following numerical approach. In other cases, we calculate the entropy and the specific heat numerically by the transfer-matrix renormalization-group method. Their low-temperature behaviors depend crucially on the properties of the zero-temperature phases. A refined ground-state phase diagram is then deduced from their low-temperature behaviors. Our findings offer an alternative way to detect those distinguishable phases experimentally.
Emergent incommensurate correlations in frustrated ferromagnetic spin-1 chains
NASA Astrophysics Data System (ADS)
Lee, Hyeong Jun; Choi, MooYoung; Jeon, Gun Sang
2017-01-01
We study frustrated ferromagnetic spin-1 chains, where the ferromagnetic nearest-neighbor coupling competes with the antiferromagnetic next-nearest-neighbor coupling. We use the density-matrix renormalization group to obtain the ground states. Through the analysis of spin-spin correlations we identify the double Haldane phase as well as the ferromagnetic phase. It is shown that the ferromagnetic coupling leads to incommensurate correlations in the double Haldane phase. Such short-range correlations transform continuously into the ferromagnetic instability at the transition to the ferromagnetic phase. We also compare the results with the spin-1/2 and classical spin systems and discuss the string orders in the system.
Disordered ground states in a quantum frustrated spin chain with side chains
NASA Astrophysics Data System (ADS)
Takano, Ken'Ichi; Hida, Kazuo
2008-04-01
We study a frustrated mixed spin chain with side chains, where the spin species and the exchange interactions are spatially varied. A nonlinear σ model method is formulated for this model, and a phase diagram with two disordered spin-gap phases is obtained for typical cases. Among them, we examine the case with a main chain, which consists of an alternating array of spin-1 and spin- (1)/(2) sites, and side chains, each of which consists of a single spin- (1)/(2) site, in great detail. Based on numerical, perturbational, and variational approaches, we propose a singlet cluster solid picture for each phase, where the ground state is expressed as a tensor product of local singlet states.
Event-chain Monte Carlo for classical continuous spin models
NASA Astrophysics Data System (ADS)
Michel, Manon; Mayer, Johannes; Krauth, Werner
2015-10-01
We apply the event-chain Monte Carlo algorithm to classical continuum spin models on a lattice and clarify the condition for its validity. In the two-dimensional XY model, it outperforms the local Monte Carlo algorithm by two orders of magnitude, although it remains slower than the Wolff cluster algorithm. In the three-dimensional XY spin glass model at low temperature, the event-chain algorithm is far superior to the other algorithms.
Dislocation-mediated melting of one-dimensional Rydberg crystals
Sela, Eran; Garst, Markus; Punk, Matthias
2011-08-15
We consider cold Rydberg atoms in a one-dimensional optical lattice in the Mott regime with a single atom per site at zero temperature. An external laser drive with Rabi frequency {Omega} and laser detuning {Delta} creates Rydberg excitations whose dynamics is governed by an effective spin-chain model with (quasi) long-range interactions. This system possesses intrinsically a large degree of frustration resulting in a ground-state phase diagram in the ({Delta},{Omega}) plane with a rich topology. As a function of {Delta}, the Rydberg blockade effect gives rise to a series of crystalline phases commensurate with the optical lattice that form a so-called devil's staircase. The Rabi frequency {Omega}, on the other hand, creates quantum fluctuations that eventually lead to a quantum melting of the crystalline states. Upon increasing {Omega}, we find that generically a commensurate-incommensurate transition to a floating Rydberg crystal that supports gapless phonon excitations occurs first. For even larger {Omega}, dislocations within the floating Rydberg crystal start to proliferate and a second, Kosterlitz-Thouless-Nelson-Halperin-Young dislocation-mediated melting transition finally destroys the crystalline arrangement of Rydberg excitations. This latter melting transition is generic for one-dimensional Rydberg crystals and persists even in the absence of an optical lattice. The floating phase and the concomitant transitions can, in principle, be detected by Bragg scattering of light.
The magnetization curve of spin chains with superlattice structure
NASA Astrophysics Data System (ADS)
Silva-Valencia, J.; Franco, R.
2006-10-01
The magnetization curve of the spin superlattices composed of repeat pattern of two spin- {1}/{2} XXZ chains with different anisotropy parameters was calculated using density matrix renormalization group. We observe a nontrivial plateau with magnetization value given by the relative sizes of the subchains.
Criticality without Frustration for Quantum Spin-1 Chains
NASA Astrophysics Data System (ADS)
Bravyi, Sergey; Caha, Libor; Movassagh, Ramis; Nagaj, Daniel; Shor, Peter W.
2012-11-01
Frustration-free (FF) spin chains have a property that their ground state minimizes all individual terms in the chain Hamiltonian. We ask how entangled the ground state of a FF quantum spin-s chain with nearest-neighbor interactions can be for small values of s. While FF spin-1/2 chains are known to have unentangled ground states, the case s=1 remains less explored. We propose the first example of a FF translation-invariant spin-1 chain that has a unique highly entangled ground state and exhibits some signatures of a critical behavior. The ground state can be viewed as the uniform superposition of balanced strings of left and right brackets separated by empty spaces. Entanglement entropy of one half of the chain scales as (1)/(2)logn+O(1), where n is the number of spins. We prove that the energy gap above the ground state is polynomial in 1/n. The proof relies on a new result concerning statistics of Dyck paths which might be of independent interest.
Criticality without frustration for quantum spin-1 chains.
Bravyi, Sergey; Caha, Libor; Movassagh, Ramis; Nagaj, Daniel; Shor, Peter W
2012-11-16
Frustration-free (FF) spin chains have a property that their ground state minimizes all individual terms in the chain Hamiltonian. We ask how entangled the ground state of a FF quantum spin-s chain with nearest-neighbor interactions can be for small values of s. While FF spin-1/2 chains are known to have unentangled ground states, the case s=1 remains less explored. We propose the first example of a FF translation-invariant spin-1 chain that has a unique highly entangled ground state and exhibits some signatures of a critical behavior. The ground state can be viewed as the uniform superposition of balanced strings of left and right brackets separated by empty spaces. Entanglement entropy of one half of the chain scales as 1/2 log n+O(1), where n is the number of spins. We prove that the energy gap above the ground state is polynomial in 1/n. The proof relies on a new result concerning statistics of Dyck paths which might be of independent interest.
Entanglement resonance in driven spin chains
NASA Astrophysics Data System (ADS)
Galve, Fernando; Zueco, David; Kohler, Sigmund; Lutz, Eric; Hänggi, Peter
2009-03-01
We consider a spin-1/2 anisotropic XY model with time-dependent spin-spin coupling as means of creating long-distance entanglement. We predict the emergence of significant entanglement between the first spin and the last spin whenever the ac part of the coupling has a frequency matching the Zeeman splitting. In particular, we find that the concurrence assumes its maximum with a vanishing dc part. Mapping the time-dependent Hamiltonian within a rotating-wave approximation to an effective static model provides qualitative and quantitative understanding of this entanglement resonance. Numerical results for the duration of the entanglement creation and its length dependence substantiate the effective static picture.
Quantum gates controlled by spin chain soliton excitations
Cuccoli, Alessandro; Nuzzi, Davide; Vaia, Ruggero; Verrucchi, Paola
2014-05-07
Propagation of soliton-like excitations along spin chains has been proposed as a possible way for transmitting both classical and quantum information between two distant parties with negligible dispersion and dissipation. In this work, a somewhat different use of solitons is considered. Solitons propagating along a spin chain realize an effective magnetic field, well localized in space and time, which can be exploited as a means to manipulate the state of an external spin (i.e., a qubit) that is weakly coupled to the chain. We have investigated different couplings between the qubit and the chain, as well as different soliton shapes, according to a Heisenberg chain model. It is found that symmetry properties strongly affect the effectiveness of the proposed scheme, and the most suitable setups for implementing single qubit quantum gates are singled out.
Spin Order and Phase Transitions in Chains of Polariton Condensates.
Ohadi, H; Ramsay, A J; Sigurdsson, H; Del Valle-Inclan Redondo, Y; Tsintzos, S I; Hatzopoulos, Z; Liew, T C H; Shelykh, I A; Rubo, Y G; Savvidis, P G; Baumberg, J J
2017-08-11
We demonstrate that multiply coupled spinor polariton condensates can be optically tuned through a sequence of spin-ordered phases by changing the coupling strength between nearest neighbors. For closed four-condensate chains these phases span from ferromagnetic (FM) to antiferromagnetic (AFM), separated by an unexpected crossover phase. This crossover phase is composed of alternating FM-AFM bonds. For larger eight-condensate chains, we show the critical role of spatial inhomogeneities and demonstrate a scheme to overcome them and prepare any desired spin state. Our observations thus demonstrate a fully controllable nonequilibrium spin lattice.
Spin Order and Phase Transitions in Chains of Polariton Condensates
NASA Astrophysics Data System (ADS)
Ohadi, H.; Ramsay, A. J.; Sigurdsson, H.; del Valle-Inclan Redondo, Y.; Tsintzos, S. I.; Hatzopoulos, Z.; Liew, T. C. H.; Shelykh, I. A.; Rubo, Y. G.; Savvidis, P. G.; Baumberg, J. J.
2017-08-01
We demonstrate that multiply coupled spinor polariton condensates can be optically tuned through a sequence of spin-ordered phases by changing the coupling strength between nearest neighbors. For closed four-condensate chains these phases span from ferromagnetic (FM) to antiferromagnetic (AFM), separated by an unexpected crossover phase. This crossover phase is composed of alternating FM-AFM bonds. For larger eight-condensate chains, we show the critical role of spatial inhomogeneities and demonstrate a scheme to overcome them and prepare any desired spin state. Our observations thus demonstrate a fully controllable nonequilibrium spin lattice.
Magnonic analog of relativistic Zitterbewegung in an antiferromagnetic spin chain
NASA Astrophysics Data System (ADS)
Wang, Weiwei; Gu, Chenjie; Zhou, Yan; Fangohr, Hans
2017-07-01
We theoretically investigate the spin-wave (magnon) excitations in a classical antiferromagnetic spin chain with easy-axis anisotropy. We obtain a Dirac-like equation by linearizing the Landau-Lifshitz-Gilbert equation in this antiferromagnetic system, in contrast to the ferromagnetic system in which a Schrödinger-type equation is derived. The Hamiltonian operator in the Dirac-like equation is a pseudo-Hermitian. We compute and demonstrate relativistic Zitterbewegung (trembling motion) in the antiferromagnetic spin chain by measuring the expectation values of the wave-packet position.
Birth and death processes and quantum spin chains
NASA Astrophysics Data System (ADS)
Grünbaum, F. Alberto; Vinet, Luc; Zhedanov, Alexei
2013-06-01
This paper underscores the intimate connection between the quantum walks generated by certain semi-infinite spin chain Hamiltonians and classical birth and death processes. It is observed that transition amplitudes between single excitation states of the spin chains have an expression in terms of orthogonal polynomials which is analogous to the Karlin-McGregor representation formula of the transition probability functions for classes of birth and death processes. As an application, we present a characterization of spin systems for which the probability to return to the point of origin at some time is 1 or almost 1.
NASA Astrophysics Data System (ADS)
Choi, Hwan Bin; Lee, Ji-Woo
2017-09-01
We study quantum phase transitions of a XXZ spin model with spin S = 1/2 and 1 in one dimension. The XXZ spin chain is one of basic models in understanding various one-dimensional magnetic materials. To study this model, we construct infinite-lattice matrix product state (iMPS), which is a tensor product form for a one-dimensional many-body quantum wave function. By using timeevolution- block-decimation method (TEBD) on iMPS, we obtain the ground states of the XXZ model at zero temperature. This method is very delicate in calculating ground states so that we developed a reliable method of finding the ground state with the dimension of entanglement coefficients up to 300, which is beyond the previous works. By analyzing ground-state energies, half-chain entanglement entropies, and entanglement spectrum, we found the signatures of quantum phase transitions between ferromagnetic phase, XY phase, Haldane phase, and antiferromagnetic phase.
Fluctuations in a Spin Chain and the Entanglement Hamiltonian
NASA Astrophysics Data System (ADS)
Turner, Ari; Demler, Eugene
2014-03-01
How are quantum fluctuations and thermal fluctuations different in many-body systems? I will compare the variance of the fluctuations of spin in a segment of a spin chain in the ground state and at a finite temperature, showing that fluctuations in the ground state are much more correlated than in the thermal state. The full distribution function of spin can also be determined, and is non-Gaussian. These effects could possibly be measured in a chain of sodium atoms in an optical lattice. The method involves mapping the system to an imaginary thermal system called the ``entanglement Hamiltonian.'' Measuring the ground state fluctuations of the spin chain gives an indirect way of measuring the entanglement Hamiltonian.
Local Spin Relaxation within the Random Heisenberg Chain
NASA Astrophysics Data System (ADS)
Herbrych, J.; Kokalj, J.; Prelovšek, P.
2013-10-01
Finite-temperature local dynamical spin correlations Snn(ω) are studied numerically within the random spin-1/2 antiferromagnetic Heisenberg chain. The aim is to explain measured NMR spin-lattice relaxation times in BaCu2(Si0.5Ge0.5)2O7, which is the realization of a random spin chain. In agreement with experiments we find that the distribution of relaxation times within the model shows a very large span similar to the stretched-exponential form. The distribution is strongly reduced with increasing T, but stays finite also in the high-T limit. Anomalous dynamical correlations can be associated with the random singlet concept but not directly with static quantities. Our results also reveal the crucial role of the spin anisotropy (interaction), since the behavior is in contrast with the ones for the XX model, where we do not find any significant T dependence of the distribution.
The topological basis realization and the corresponding XXX spin chain
NASA Astrophysics Data System (ADS)
Sun, C. F.; Xue, K.; Wang, G. C.; Zhou, C. C.; Du, G. J.
2011-06-01
In this paper, it is shown that the XXX model can be constructed from the Temperley-Lieb algebra (TLA) generator. We find that the topological basis states are the two eigenstaes of a closed four-qubit Heisenberg XXX spin chain. Specifically, the spin single states and the energy single state of the system all fall on the topological basis states. It is worth mentioning that for the closed 2N-qubit (N=2, 3, 4, ...) Heisenberg XXX spin chain, all the topological basis states for 2N particles are the spin single states of the system. And the number of the topological basis states is equal to the number of the spin single states of the system, which is \\frac{(2N)!}{N!(N+1)!} .
Fulde-Ferrell-Larkin-Ovchinnikov critical polarization in one-dimensional fermionic optical lattices
NASA Astrophysics Data System (ADS)
França, Vivian V.; Hörndlein, Dominik; Buchleitner, Andreas
2012-09-01
We deduce an expression for the critical polarization PC below which the Fulde-Ferrell-Larkin-Ovchinnikov state emerges in one-dimensional lattices with spin-imbalanced populations. We provide and explore the phase diagram of unconfined chains as a function of polarization, interaction, and particle density. For harmonically confined systems, we supply a quantitative mapping, which also allows applying our phase diagram for confined chains. We find analytically and confirm numerically that the upper bound for the critical polarization is universal: PCmax=1/3 for any density, interaction, and confinement strength.
Long-distance entanglement and quantum teleportation in XX spin chains
Campos Venuti, L.; Giampaolo, S. M.; Illuminati, F.; Zanardi, P.
2007-11-15
Isotropic XX models of one-dimensional spin-1/2 chains are investigated with the aim to elucidate the formal structure and the physical properties that allow these systems to act as channels for long-distance, high-fidelity quantum teleportation. We introduce two types of models: (i) open, dimerized XX chains, and (ii) open XX chains with small end bonds. For both models we obtain the exact expressions for the end-to-end correlations and the scaling of the energy gap with the length of the chain. We determine the end-to-end concurrence and show that model (i) supports true long-distance entanglement at zero temperature, while model (ii) supports 'quasi-long-distance' entanglement that slowly falls off with the size of the chain. Due to the different scalings of the gaps, respectively exponential for model (i) and algebraic in model (ii), we demonstrate that the latter allows for efficient qubit teleportation with high fidelity in sufficiently long chains even at moderately low temperatures.
Exchange anisotropy as mechanism for spin-stripe formation in frustrated spin chains
NASA Astrophysics Data System (ADS)
Pregelj, M.; Zaharko, O.; Herak, M.; Gomilšek, M.; Zorko, A.; Chapon, L. C.; Bourdarot, F.; Berger, H.; Arčon, D.
2016-08-01
We investigate the spin-stripe mechanism responsible for the peculiar nanometer modulation of the incommensurate magnetic order that emerges between the vector-chiral and the spin-density-wave phase in the frustrated zigzag spin-1/2 chain compound β -TeVO4 . A combination of magnetic-torque, neutron-diffraction, and spherical-neutron-polarimetry measurements is employed to determine the complex magnetic structures of all three ordered phases. Based on these results, we develop a simple phenomenological model, which exposes the exchange anisotropy as the key ingredient for the spin-stripe formation in frustrated spin systems.
Electronic structure of one-dimensional cuprates
NASA Astrophysics Data System (ADS)
Maiti, K.; Sarma, D. D.; Mizokawa, T.; Fujimori, A.
1998-01-01
We have investigated the electronic structures of one-dimensional antiferromagnetic insulators Ca2CuO3 and Sr2CuO3 combining electron spectroscopic measurements and various calculations. While calculations based on a local-spin-density approach for the real magnetic structures fail to yield an insulating state, from our experiments we estimate the intrinsic band gaps in these materials to be about 1.7 eV (Ca2CuO3) and 1.5 eV (Sr2CuO3). Analysis of the core-level and the valence-band spectra in terms of model many-body Hamiltonians show that the charge-transfer energy Δ for these one-dimensional systems is significantly smaller than other cuprates, such as the high-Tc oxides (two-dimensional) and CuO (three-dimensional). Such a small Δ suggests the presence of the bare upper Hubbard band within the oxygen p bandwidth and thus provides an example of a correlated covalent insulator.
Geometrically Constructed Markov Chain Monte Carlo Study of Quantum Spin-phonon Complex Systems
NASA Astrophysics Data System (ADS)
Suwa, Hidemaro
2013-03-01
We have developed novel Monte Carlo methods for precisely calculating quantum spin-boson models and investigated the critical phenomena of the spin-Peierls systems. Three significant methods are presented. The first is a new optimization algorithm of the Markov chain transition kernel based on the geometric weight allocation. This algorithm, for the first time, satisfies the total balance generally without imposing the detailed balance and always minimizes the average rejection rate, being better than the Metropolis algorithm. The second is the extension of the worm (directed-loop) algorithm to non-conserved particles, which cannot be treated efficiently by the conventional methods. The third is the combination with the level spectroscopy. Proposing a new gap estimator, we are successful in eliminating the systematic error of the conventional moment method. Then we have elucidated the phase diagram and the universality class of the one-dimensional XXZ spin-Peierls system. The criticality is totally consistent with the J1 -J2 model, an effective model in the antiadiabatic limit. Through this research, we have succeeded in investigating the critical phenomena of the effectively frustrated quantum spin system by the quantum Monte Carlo method without the negative sign. JSPS Postdoctoral Fellow for Research Abroad
Measurement-based teleportation along quantum spin chains.
Barjaktarevic, J P; McKenzie, R H; Links, J; Milburn, G J
2005-12-02
We examine the teleportation of an unknown spin-1/2 quantum state along a quantum spin chain with an even number of sites. Our protocol, using a sequence of Bell measurements, may be viewed as an iterated version of the 2-qubit protocol of C. H. Bennett et al. [Phys. Rev. Lett. 70, 1895 (1993)]. A decomposition of the Hilbert space of the spin chain into 4 vector spaces, called Bell subspaces, is given. It is established that any state from a Bell subspace may be used as a channel to perform unit fidelity teleportation. The space of all spin-0 many-body states, which includes the ground states of many known antiferromagnetic systems, belongs to a common Bell subspace. A channel-dependent teleportation parameter [symbol: see text] is introduced, and a bound on the teleportation fidelity is given in terms of [symbol: see text].
Subspace controllability of spin-1/2 chains with symmetries
NASA Astrophysics Data System (ADS)
Wang, Xiaoting; Burgarth, Daniel; Schirmer, S.
2016-11-01
We develop a technique to prove simultaneous subspace controllability on multiple invariant subspaces, which specifically enables us study the controllability properties of spin systems that are not amenable to standard controllability arguments based on energy level connectivity graphs or simple induction arguments on the length of the chain. The technique is applied to establish simultaneous subspace controllability for Heisenberg spin chains subject to limited local controls. This model is theoretically important and the controllability result shows that a single control can be sufficient for complete controllability of an exponentially large subspace and universal quantum computation in the exponentially large subspace. The controllability results are extended to prove subspace controllability in the presence of control field leakage and discuss minimal control resources required to achieve controllability over the entire spin chain space.
Propagation of nonclassical correlations across a quantum spin chain
Campbell, S.; Apollaro, T. J. G.; Di Franco, C.; Banchi, L.; Cuccoli, A.; Vaia, R.; Plastina, F.; Paternostro, M.
2011-11-15
We study the transport of quantum correlations across a chain of interacting spin-1/2 particles. As a quantitative figure of merit, we choose a symmetric version of quantum discord and compare it with the transported entanglement, addressing various operating regimes of the spin medium. Discord turns out to be better transported for a wide range of working points and initial conditions of the system. We relate this behavior to the efficiency of propagation of a single excitation across the spin chain. Moreover, we point out the role played by a magnetic field in the dynamics of discord in the effective channel embodied by the chain. Our analysis can be interestingly extended to transport processes in more complex networks and the study of nonclassical correlations under general quantum channels.
Rogue waves and breathers in Heisenberg spin chain
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Aritra K.; Vyas, Vivek M.; Panigrahi, Prasanta K.
2015-07-01
Following the connection of the non-linear Schrödinger equation with the continuum Heisenberg spin chain, we find the rogue soliton equivalent in the spin system. The breathers are also mapped to the corresponding space or time localized oscillatory modes, through the moving curve analogy. The spatio-temporal evolution of the curvature and torsion of the curve, underlying these dynamical systems, are explicated to illustrate the localization property of the rogue waves.
Effects of Quantum Spin-1 /2 Impurities on the Magnetic Properties of Zigzag Spin Chains
NASA Astrophysics Data System (ADS)
Karmakar, Koushik; Skoulatos, Markos; Prando, Giacomo; Roessli, Bertran; Stuhr, Uwe; Hammerath, Franziska; Rüegg, Christian; Singh, Surjeet
2017-03-01
We investigate the effect of Co2 + (spin-1 /2 ) impurities on the magnetic ground state and low-lying spin excitations of the quasione-dimensional spin-1 /2 antiferromagnet SrCuO2 by means of neutron scattering, muon spin spectroscopy, and bulk (ac and dc) magnetic susceptibilities. We found that dilute Co doping induces an Ising-like anisotropy and enhances the magnetic ordering temperature rather significantly, but preserves the gapless nature of the spin excitations. These results are in apparent contradiction with the recent studies of Ni (spin-1) doped SrCuO2 . Low-temperature magnetic behavior of the Co-doped zigzag chains in SrCuO2 reveals the presence of a weak geometrical spin frustration.
Effects of Quantum Spin-1/2 Impurities on the Magnetic Properties of Zigzag Spin Chains.
Karmakar, Koushik; Skoulatos, Markos; Prando, Giacomo; Roessli, Bertran; Stuhr, Uwe; Hammerath, Franziska; Rüegg, Christian; Singh, Surjeet
2017-03-10
We investigate the effect of Co^{2+} (spin-1/2) impurities on the magnetic ground state and low-lying spin excitations of the quasione-dimensional spin-1/2 antiferromagnet SrCuO_{2} by means of neutron scattering, muon spin spectroscopy, and bulk (ac and dc) magnetic susceptibilities. We found that dilute Co doping induces an Ising-like anisotropy and enhances the magnetic ordering temperature rather significantly, but preserves the gapless nature of the spin excitations. These results are in apparent contradiction with the recent studies of Ni (spin-1) doped SrCuO_{2}. Low-temperature magnetic behavior of the Co-doped zigzag chains in SrCuO_{2} reveals the presence of a weak geometrical spin frustration.
Nonequilibrium Phase Transition in a Periodically Driven XY Spin Chain
NASA Astrophysics Data System (ADS)
Prosen, Tomaž; Ilievski, Enej
2011-08-01
We present a general formulation of Floquet states of periodically time-dependent open Markovian quasifree fermionic many-body systems in terms of a discrete Lyapunov equation. Illustrating the technique, we analyze periodically kicked XY spin-(1)/(2) chain which is coupled to a pair of Lindblad reservoirs at its ends. A complex phase diagram is reported with reentrant phases of long range and exponentially decaying spin-spin correlations as some of the system’s parameters are varied. The structure of phase diagram is reproduced in terms of counting nontrivial stationary points of Floquet quasiparticle dispersion relation.
On Transport Properties of Isotropic Quasiperiodic XY Spin Chains
NASA Astrophysics Data System (ADS)
Kachkovskiy, Ilya
2016-07-01
We consider isotropic XY spin chains whose magnetic potentials are quasiperiodic and the effective one-particle Hamiltonians have absolutely continuous spectra. For a wide class of such XY spin chains, we obtain lower bounds on their Lieb-Robinson velocities {mathfrak{v}} in terms of group velocities of their effective Hamiltonians: mathfrak{v}{≥slant} {mathop {ess sup}_{[0,1]}}2/πdE/dN. where E is considered as a function of the integrated density of states.
Nonequilibrium electronic transport in a one-dimensional Mott insulator
Heidrich-Meisner, F.; Gonzalez, Ivan; Al-Hassanieh, K. A.; Feiguin, A. E.; Rozenberg, M. J.; Dagotto, Elbio R
2010-01-01
We calculate the nonequilibrium electronic transport properties of a one-dimensional interacting chain at half filling, coupled to noninteracting leads. The interacting chain is initially in a Mott insulator state that is driven out of equilibrium by applying a strong bias voltage between the leads. For bias voltages above a certain threshold we observe the breakdown of the Mott insulator state and the establishment of a steady-state elec- tronic current through the system. Based on extensive time-dependent density-matrix renormalization-group simulations, we show that this steady-state current always has the same functional dependence on voltage, independent of the microscopic details of the model and we relate the value of the threshold to the Lieb-Wu gap. We frame our results in terms of the Landau-Zener dielectric breakdown picture. Finally, we also discuss the real-time evolution of the current, and characterize the current-carrying state resulting from the breakdown of the Mott insulator by computing the double occupancy, the spin structure factor, and the entanglement entropy.
NASA Astrophysics Data System (ADS)
Sahling, S.; Remenyi, G.; Paulsen, C.; Monceau, P.; Saligrama, V.; Marin, C.; Revcolevschi, A.; Regnault, L. P.; Raymond, S.; Lorenzo, J. E.
2015-03-01
Entanglement is a concept that has defied common sense since the discovery of quantum mechanics. Two particles are said to be entangled when the quantum state of each particle cannot be described independently, no matter how far apart in space and time the two particles are. We demonstrate experimentally that unpaired spins separated by several hundred ångström entangle through a collection of spin singlets made up of antiferromagnetic spin-1/2 chains in a bulk material. Low-temperature magnetization and specific heat studies as a function of magnetic field reveal the occurrence of very dilute spin dimers and at least two quantum phase transitions related to the breaking of excited local triplets. The mechanism at the origin of the unpaired spins inside the quantum chains is the inter-modulation potential between two sublattices, and may be replicated using well-designed synthetic multilayers.
NASA Astrophysics Data System (ADS)
Zeisner, J.; Brockmann, M.; Zimmermann, S.; Weiße, A.; Thede, M.; Ressouche, E.; Povarov, K. Yu.; Zheludev, A.; Klümper, A.; Büchner, B.; Kataev, V.; Göhmann, F.
2017-07-01
We compare theoretical results for electron spin resonance (ESR) properties of the Heisenberg-Ising Hamiltonian with ESR experiments on the quasi-one-dimensional magnet Cu (py) 2Br2 (CPB). Our measurements were performed over a wide frequency and temperature range giving insight into the spin dynamics, spin structure, and magnetic anisotropy of this compound. By analyzing the angular dependence of ESR parameters (resonance shift and linewidth) at room temperature, we show that the two weakly coupled inequivalent spin-chain types inside the compound are well described by Heisenberg-Ising chains with their magnetic anisotropy axes perpendicular to the chain direction and almost perpendicular to each other. We further determine the full g tensor from these data. In addition, the angular dependence of the linewidth at high temperatures gives us access to the exponent of the algebraic decay of a dynamical correlation function of the isotropic Heisenberg chain. From the temperature dependence of static susceptibilities, we extract the strength of the exchange coupling (J /kB=52.0 K ) and the anisotropy parameter (δ ≈-0.02 ) of the model Hamiltonian. An independent compatible value of δ is obtained by comparing the exact prediction for the resonance shift at low temperatures with high-frequency ESR data recorded at 4 K . The spin structure in the ordered state implied by the two (almost) perpendicular anisotropy axes is in accordance with the propagation vector determined from neutron scattering experiments. In addition to undoped samples, we study the impact of partial substitution of Br by Cl ions on spin dynamics. From the dependence of the ESR linewidth on the doping level, we infer an effective decoupling of the anisotropic component J δ from the isotropic exchange J in these systems.
Random matrix theory and critical phenomena in quantum spin chains
NASA Astrophysics Data System (ADS)
Hutchinson, J.; Keating, J. P.; Mezzadri, F.
2015-09-01
We compute critical properties of a general class of quantum spin chains which are quadratic in the Fermi operators and can be solved exactly under certain symmetry constraints related to the classical compact groups $U(N)$, $O(N)$ and $Sp(2N)$. In particular we calculate critical exponents $s$, $\
Long-range interactions in antiferromagnetic quantum spin chains
NASA Astrophysics Data System (ADS)
Bravo, B.; Cabra, D. C.; Gómez Albarracín, F. A.; Rossini, G. L.
2017-08-01
We study the role of long-range dipolar interactions on antiferromagnetic spin chains, from the classical S →∞ limit to the deep quantum case S =1 /2 , including a transverse magnetic field. To this end, we combine different techniques such as classical energy minima, classical Monte Carlo, linear spin waves, bosonization, and density matrix renormalization group (DMRG). We find a phase transition from the already reported dipolar ferromagnetic region to an antiferromagnetic region for high enough antiferromagnetic exchange. Thermal and quantum fluctuations destabilize the classical order before reaching magnetic saturation in both phases, and also close to zero field in the antiferromagnetic phase. In the extreme quantum limit S =1 /2 , extensive DMRG computations show that the main phases remain present with transition lines to saturation significatively shifted to lower fields, in agreement with the bosonization analysis. The overall picture maintains a close analogy with the phase diagram of the anisotropic XXZ spin chain in a transverse field.
Two-dimensional interaction of spin chains in the Si(553)-Au nanowire system
NASA Astrophysics Data System (ADS)
Hafke, B.; Frigge, T.; Witte, T.; Krenzer, B.; Aulbach, J.; Schäfer, J.; Claessen, R.; Erwin, S. C.; Horn-von Hoegen, M.
2016-10-01
Adsorption of Au on Si(553) results in the self-assembly of highly ordered step arrays of one-dimensional (1D) Au atomic wires along the step direction. Charge transfer from the terrace to the step edge causes every third Si atom at the step edge to exhibit a partially filled dangling bond hosting a single fully spin-polarized electron which forms in an ordered 1D spin chain along the step. The interstep correlation of this threefold periodicity in neighboring Si step edges and the geometry of the unit cell has been determined by means of high-resolution spot profile analysis low-energy electron diffraction, scanning tunneling microscopy, and density functional theory. While the twofold periodicity of the Au wires exhibits a weak interwire interaction, leading to streaks in the diffraction pattern, the correlation of the Si step edge atoms is by far a stronger interaction, resulting in clear spots. The corresponding unit cell spanned by threefold ordered step edge atoms can be described as a centered structure which is magnetically frustrated and may stabilize a (two-dimensional) quantum spin liquid.
Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains
NASA Astrophysics Data System (ADS)
Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.
2016-09-01
The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.
Entropy and correlation functions of a driven quantum spin chain
Cherng, R. W.; Levitov, L. S.
2006-04-15
We present an exact solution for a quantum spin chain driven through its critical points. Our approach is based on a many-body generalization of the Landau-Zener transition theory, applied to a fermionized spin Hamiltonian. The resulting nonequilibrium state of the system, while being a pure quantum state, has local properties of a mixed state characterized by finite entropy density associated with Kibble-Zurek defects. The entropy and the finite spin correlation length are functions of the rate of sweep through the critical point. We analyze the anisotropic XY spin-1/2 model evolved with a full many-body evolution operator. With the help of Toeplitz determinant calculus, we obtain an exact form of correlation functions. The properties of the evolved system undergo an abrupt change at a certain critical sweep rate, signaling the formation of ordered domains. We link this phenomenon to the behavior of complex singularities of the Toeplitz generating function.
Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions
Liu, Yu-Shen; Zhang, Xue; Feng, Jin-Fu; Wang, Xue-Feng
2014-06-16
We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T = 25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.
Spin and topological order in a periodically driven spin chain
NASA Astrophysics Data System (ADS)
Russomanno, Angelo; Friedman, Bat-el; Dalla Torre, Emanuele G.
2017-07-01
The periodically driven quantum Ising chain has recently attracted a large attention in the context of Floquet engineering. In addition to the common paramagnet and ferromagnet, this driven model can give rise to new topological phases. In this work, we systematically explore its quantum phase diagram by examining the properties of its Floquet ground state. We specifically focus on driving protocols with time-reversal invariant points, and demonstrate the existence of an infinite number of distinct phases. These phases are separated by second-order quantum phase transitions, accompanied by continuous changes of local and string order parameters, as well as sudden changes of a topological winding number and of the number of protected edge states. When one of these phase transitions is adiabatically crossed, the correlator associated to the order parameter is nonvanishing over a length scale which shows a Kibble-Zurek scaling. In some phases, the Floquet ground state spontaneously breaks the discrete time-translation symmetry of the Hamiltonian. Our findings provide a better understanding of topological phases in periodically driven clean integrable models.
Emergent quasi-one-dimensionality in a kagome magnet: A simple route to complexity
NASA Astrophysics Data System (ADS)
Gong, Shou-Shu; Zhu, Wei; Yang, Kun; Starykh, Oleg A.; Sheng, D. N.; Balents, Leon
2016-07-01
We study the ground-state phase diagram of the quantum spin-1 /2 Heisenberg model on the kagome lattice with first- (J1<0 ) , second- (J2<0 ) , and third-neighbor interactions (Jd>0 ) by means of analytical low-energy field theory and numerical density-matrix renormalization group (DMRG) studies. The results offer a consistent picture of the Jd-dominant regime in terms of three sets of spin chains weakly coupled by the ferromagnetic interchain interactions J1 ,2. When either J1 or J2 is much stronger than the other one, the model is found to support one of two cuboctohedral phases, cuboc1, and cuboc2. These cuboc states host noncoplanar long-ranged magnetic order and possess finite scalar spin chirality. However, in the compensated regime J1≃J2 , a valence bond crystal phase emerges between the two cuboc phases. We find excellent agreement between an analytical theory based on coupled spin chains and unbiased DMRG calculations, including at a very detailed level of comparison of the structure of the valence bond crystal state. To our knowledge, this is the first such comprehensive understanding of a highly frustrated two-dimensional quantum antiferromagnet. We find no evidence of either the one-dimensional gapless spin liquid or the chiral spin liquids, which were previously suggested by parton mean-field theories.
Strong-coupling ansatz for the one-dimensional Fermi gas in a harmonic potential
Levinsen, Jesper; Massignan, Pietro; Bruun, Georg M.; Parish, Meera M.
2015-01-01
A major challenge in modern physics is to accurately describe strongly interacting quantum many-body systems. One-dimensional systems provide fundamental insights because they are often amenable to exact methods. However, no exact solution is known for the experimentally relevant case of external confinement. We propose a powerful ansatz for the one-dimensional Fermi gas in a harmonic potential near the limit of infinite short-range repulsion. For the case of a single impurity in a Fermi sea, we show that our ansatz is indistinguishable from numerically exact results in both the few- and many-body limits. We furthermore derive an effective Heisenberg spin-chain model corresponding to our ansatz, valid for any spin-mixture, within which we obtain the impurity eigenstates analytically. In particular, the classical Pascal’s triangle emerges in the expression for the ground-state wave function. As well as providing an important benchmark for strongly correlated physics, our results are relevant for emerging quantum technologies, where a precise knowledge of one-dimensional quantum states is paramount. PMID:26601220
Random registry shifts in quasi-one-dimensional adsorbate systems
Schafer, J.; Erwin, S.C.; Hansmann, M.; Song, Z.; Rotenberg, E.; Kevan, S.D.; Hellberg, C.S.; Horn, K.
2003-02-18
The apparent contradiction of one-dimensional adsorbate chains on Si(111) having a 3x2 unit cell and yet a 3x1 diffraction pattern is resolved for the example of Ba/Si(111)-(3x2). Random registry shifts between adsorbate chains are observed in tunneling microscopy, with very short interchain correlation lengths. Fourier analysis provides a natural explanation for a pseudo-(3x1) diffraction pattern. Within density-functional theory such registry shifts can occur with essentially negligible energy cost, leading to entropy-driven, virtually perfect disorder. Substrate states of high symmetry and one-dimensional character are inferred to promote this phenomenon.
Random registry shifts in quasi-one-dimensional adsorbate systems
NASA Astrophysics Data System (ADS)
Schäfer, J.; Erwin, S. C.; Hansmann, M.; Song, Z.; Rotenberg, E.; Kevan, S. D.; Hellberg, C. S.; Horn, K.
2003-02-01
The apparent contradiction of one-dimensional adsorbate chains on Si(111) having a 3×2 unit cell and yet a 3×1 diffraction pattern is resolved for the example of Ba/Si(111)-(3×2). Random registry shifts between adsorbate chains are observed in tunneling microscopy, with very short interchain correlation lengths. Fourier analysis provides a natural explanation for a pseudo-(3×1) diffraction pattern. Within density-functional theory such registry shifts can occur with essentially negligible energy cost, leading to entropy-driven, virtually perfect disorder. Substrate states of high symmetry and one-dimensional character are inferred to promote this phenomenon.
Scaling behavior of spin gap of the bond alternating anisotropic spin-1/2 Heisenberg chain
Paul, Susobhan; Ghosh, Asim Kumar
2016-05-06
Scaling behavior of spin gap of a bond alternating spin-1/2 anisotropic Heisenberg chain has been studied both in ferromagnetic (FM) and antiferromagnetic (AFM) cases. Spin gap has been estimated by using exact diagonalization technique. All those quantities have been obtained for a region of anisotropic parameter Δ defined by 0≤Δ≤1. Spin gap is found to develop as soon as the non-uniformity in the alternating bond strength is introduced in the AFM regime which furthermore sustains in the FM regime as well. Scaling behavior of the spin gap has been studied by introducing scaling exponent. The variation of scaling exponents with Δ is fitted with a regular function.
Logarithmic current fluctuations in nonequilibrium quantum spin chains.
Antal, T; Krapivsky, P L; Rákos, A
2008-12-01
We study zero-temperature quantum spin chains, which are characterized by a nonvanishing current. For the XX model starting from the initial state mid R:cdots, three dots, centered upward arrow upward arrow upward arrow downward arrow downward arrow downward arrowcdots, three dots, centered we derive an exact expression for the variance of the total spin current. We show that asymptotically the variance exhibits an anomalously slow logarithmic growth; we also extract the subleading constant term. We then argue that the logarithmic growth remains valid for the XXZ model in the critical region.
Q-operators for the open Heisenberg spin chain
NASA Astrophysics Data System (ADS)
Frassek, Rouven; Szécsényi, István M.
2015-12-01
We construct Q-operators for the open spin-1/2 XXX Heisenberg spin chain with diagonal boundary matrices. The Q-operators are defined as traces over an infinite-dimensional auxiliary space involving novel types of reflection operators derived from the boundary Yang-Baxter equation. We argue that the Q-operators defined in this way are polynomials in the spectral parameter and show that they commute with transfer matrix. Finally, we prove that the Q-operators satisfy Baxter's TQ-equation and derive the explicit form of their eigenvalues in terms of the Bethe roots.
Spinon confinement in a quasi-one-dimensional anisotropic Heisenberg magnet
NASA Astrophysics Data System (ADS)
Bera, A. K.; Lake, B.; Essler, F. H. L.; Vanderstraeten, L.; Hubig, C.; Schollwöck, U.; Islam, A. T. M. N.; Schneidewind, A.; Quintero-Castro, D. L.
2017-08-01
Confinement is a process by which particles with fractional quantum numbers bind together to form quasiparticles with integer quantum numbers. The constituent particles are confined by an attractive interaction whose strength increases with increasing particle separation and, as a consequence, individual particles are not found in isolation. This phenomenon is well known in particle physics where quarks are confined in baryons and mesons. An analogous phenomenon occurs in certain spatially anisotropic magnetic insulators. These can be thought of in terms of weakly coupled chains of spins S =1 /2 , and a spin flip thus carries integer spin S =1 . The collective excitations in these systems, called spinons, turn out to carry fractional spin quantum number S =1 /2 . Interestingly, at sufficiently low temperatures the weak coupling between chains can induce an attractive interaction between pairs of spinons that increases with their separation and thus leads to confinement. In this paper, we employ inelastic neutron scattering to investigate the spinon-confinement process in the quasi-one-dimensional, spin-1/2 antiferromagnet with Heisenberg-Ising (XXZ) anisotropy SrCo2V2O8 . A wide temperature range both above and below the long-range ordering temperature TN=5.2 K is explored. Spinon excitations are observed above TN in quantitative agreement with established theory. Below TN pairs of spinons are confined and two sequences of meson-like bound states with longitudinal and transverse polarizations are observed. Several theoretical approaches are used to explain the data. These are based on a description in terms of a one-dimensional, S =1 /2 XXZ antiferromagnetic spin chain, where the interchain couplings are modeled by an effective staggered magnetic mean field. A wide range of exchange anisotropies are investigated and the parameters specific to SrCo2V2O8 are identified. Recently developed theoretical technique based on tangent-space matrix product states gives a very
Site-Selective Mott Transition in a Quasi-One-Dimensional Vanadate V6 O13
NASA Astrophysics Data System (ADS)
Shimizu, Yasuhiro; Aoyama, Satoshi; Jinno, Takaaki; Itoh, Masayuki; Ueda, Yutaka
2015-04-01
The microscopic mechanism of the metal-insulator transition is studied by orbital-resolved 51V NMR spectroscopy in a prototype of the quasi-one-dimensional system V6 O13 . We uncover that the transition involves a site-selective d orbital order lifting twofold orbital degeneracy in one of the two VO6 chains. The other chain leaves paramagnetic moments on the singly occupied dx y orbital across the transition. The two chains respectively stabilize an orbital-assisted spin-Peierls state and an antiferromagnetic long-range order in the ground state. The site-selective Mott transition may be a source of the anomalous metal and the Mott-Peierls duality.
Robust Quantum State Transfer in Random Unpolarized Spin Chains
NASA Astrophysics Data System (ADS)
Yao, N. Y.; Jiang, L.; Gorshkov, A. V.; Gong, Z.-X.; Zhai, A.; Duan, L.-M.; Lukin, M. D.
2011-01-01
We propose and analyze a new approach for quantum state transfer between remote spin qubits. Specifically, we demonstrate that coherent quantum coupling between remote qubits can be achieved via certain classes of random, unpolarized (infinite temperature) spin chains. Our method is robust to coupling-strength disorder and does not require manipulation or control over individual spins. In principle, it can be used to attain perfect state transfer over an arbitrarily long range via purely Hamiltonian evolution and may be particularly applicable in a solid-state quantum information processor. As an example, we demonstrate that it can be used to attain strong coherent coupling between nitrogen-vacancy centers separated by micrometer distances at room temperature. Realistic imperfections and decoherence effects are analyzed.
Fluctuations of the heat exchanged between two quantum spin chains.
Landi, Gabriel T; Karevski, Dragi
2016-03-01
The statistics of the heat exchanged between two quantum XX spin chains prepared at different temperatures is studied within the assumption of weak coupling. This provides simple formulas for the average heat and its corresponding characteristic function, from which the probability distribution may be computed numerically. These formulas are valid for arbitrary sizes and therefore allow us to analyze the role of the thermodynamic limit in this nonequilibrium setting. It is found that all thermodynamic quantities are extremely sensitive to the quantum phase transition of the XX chain.
Optimization of excitation transfer in a spin chain
Gurman, Vladimir I.; Guseva, Irina S.; Fesko, Oles V.
2016-06-08
A revised formulation of the problem of fastest transfer of the excitation in a spin chain is considered on the base of Shrödinger equation which Hamiltonian depends linearly on control. It is taken into account that the excitation of the first or last spin means that it has greatest amplitude equal to the chain invariant whereas its phase is undefined and can be considered as an additional control variable. The role of this additional control is analyzed via transformation of the original problem with unbounded linear control to the regular derived problem known from the theory of degenerate problems [1, 2], in the same way as in [2]. The overall procedure is demonstrated in computational experiments with the use of visual examples.
Optimization of excitation transfer in a spin chain
NASA Astrophysics Data System (ADS)
Gurman, Vladimir I.; Guseva, Irina S.; Fesko, Oles V.
2016-06-01
A revised formulation of the problem of fastest transfer of the excitation in a spin chain is considered on the base of Shrödinger equation which Hamiltonian depends linearly on control. It is taken into account that the excitation of the first or last spin means that it has greatest amplitude equal to the chain invariant whereas its phase is undefined and can be considered as an additional control variable. The role of this additional control is analyzed via transformation of the original problem with unbounded linear control to the regular derived problem known from the theory of degenerate problems [1, 2], in the same way as in [2]. The overall procedure is demonstrated in computational experiments with the use of visual examples.
Exact solution of the one-dimensional super-symmetric t-J model with unparallel boundary fields
NASA Astrophysics Data System (ADS)
Zhang, Xin; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2014-04-01
The exact solution of the one-dimensional super-symmetric t-J model under generic integrable boundary conditions is obtained via the Bethe ansatz methods. With the coordinate Bethe ansatz, the corresponding R-matrix and K-matrices are derived for the second eigenvalue problem associated with spin degrees of freedom. It is found that the second eigenvalue problem can be transformed into that of the transfer matrix of the inhomogeneous XXX spin chain, which allows us to obtain the spectrum of the Hamiltonian and the associated Bethe ansatz equations by the off-diagonal Bethe ansatz method.
NASA Astrophysics Data System (ADS)
Wu, Wei; Xu, Jing-Bo
2016-08-01
We investigate the quantum phase transitions of spin systems in one and two dimensions by employing trace distance and multipartite entanglement along with the real-space quantum renormalization group method. As illustration examples, a one-dimensional and a two-dimensional XY models are considered. It is shown that the quantum phase transitions of these spin-chain systems can be revealed by the singular behaviors of the first derivatives of renormalized trace distance and multipartite entanglement in the thermodynamics limit. Moreover, we find that the renormalized trace distance and multipartite entanglement obey certain universal exponential-type scaling laws in the vicinity of the quantum critical points.
Spin structure factors of Heisenberg spin chain in the presence of anisotropy and magnetic field
NASA Astrophysics Data System (ADS)
Rezania, H.
2017-02-01
We have theoretically studied the spin structure factors of spin chain in the presence of longitudinal field and transverse anisotropy. The possible effects of easy axis magnetization are investigated in terms of anisotropy in the Heisenberg interactions. This anisotropy is considered for exchange coupling constants perpendicular to magnetic field direction. The original spin model hamiltonian is mapped to a bosonic model via a hard core bosonic transformation where an infinite hard core repulsion is imposed to constrain one boson occupation per site. Using Green's function approach, the energy spectrum of quasiparticle excitation has been obtained. The spectrum of the bosonic gas has been implemented in order to obtain two particle propagator which corresponds to spin structure factor of original Heisenberg chain model Hamiltonian. The results show the position of peak in the longitudinal structure factor at fixed value for anisotropy moves to higher frequency with magnetic field. Also the intensity of dynamical structure factor decreases with magnetic field. A small dependence of longitudinal dynamical spin structure factor on the anisotropy is observed for fixed value of magnetic field. Our results show longitudinal static structure factor is found to be monotonically increasing with magnetic field due to increase of spins aligning along magnetic field. Furthermore the dispersion behaviors of static longitudinal and transverse structure factors for different magnetic fields and anisotropy parameters are addressed.
Entanglement entropy in quantum spin chains with broken reflection symmetry
Kadar, Zoltan; Zimboras, Zoltan
2010-09-15
We investigate the entanglement entropy of a block of L sites in quasifree translation-invariant spin chains concentrating on the effect of reflection-symmetry breaking. The Majorana two-point functions corresponding to the Jordan-Wigner transformed fermionic modes are determined in the most general case; from these, it follows that reflection symmetry in the ground state can only be broken if the model is quantum critical. The large L asymptotics of the entropy are calculated analytically for general gauge-invariant models, which have, until now, been done only for the reflection-symmetric sector. Analytical results are also derived for certain nongauge-invariant models (e.g., for the Ising model with Dzyaloshinskii-Moriya interaction). We also study numerically finite chains of length N with a nonreflection-symmetric Hamiltonian and report that the reflection symmetry of the entropy of the first L spins is violated but the reflection-symmetric Calabrese-Cardy formula is recovered asymptotically. Furthermore, for noncritical reflection-symmetry-breaking Hamiltonians, we find an anomaly in the behavior of the saturation entropy as we approach the critical line. The paper also provides a concise but extensive review of the block-entropy asymptotics in translation-invariant quasifree spin chains with an analysis of the nearest-neighbor case and the enumeration of the yet unsolved parts of the quasifree landscape.
NASA Astrophysics Data System (ADS)
Carrasco, José A.; Finkel, Federico; González-López, Artemio; Rodríguez, Miguel A.
2017-01-01
We study the critical behavior and the ground-state entanglement of a large class of su (1 |1 ) supersymmetric spin chains with a general (not necessarily monotonic) dispersion relation. We show that this class includes several relevant models, with both short- and long-range interactions of a simple form. We determine the low temperature behavior of the free energy per spin, and deduce that the models considered have a critical phase in the same universality class as a (1 +1 ) -dimensional conformal field theory (CFT) with central charge equal to the number of connected components of the Fermi sea. We also study the Rényi entanglement entropy of the ground state, deriving its asymptotic behavior as the block size tends to infinity. In particular, we show that this entropy exhibits the logarithmic growth characteristic of (1 +1 ) -dimensional CFTs and one-dimensional (fermionic) critical lattice models, with a central charge consistent with the low-temperature behavior of the free energy. Our results confirm the widely believed conjecture that the critical behavior of fermionic lattice models is completely determined by the topology of their Fermi surface.
Nonreciprocal spin wave elementary excitation in dislocated dimerized Heisenberg chains.
Liu, Wanguo; Shen, Yang; Fang, Guisheng; Jin, Chongjun
2016-05-18
A mechanism for realizing nonreciprocal elementary excitation of spin wave (SW) is proposed. We study a reference model which describes a magnonic crystal (MC) formed by two Heisenberg chains with a lateral displacement (dislocation) and a longitudinal spacer, and derive a criterion to judge whether the elementary excitation spectra are reciprocal in this ferromagnetic lattice. An analytical method based on the spin precession equation is used to solve the elementary excitation spectra. The solution is related to a key factor, the spatio-temporal structure factor [Formula: see text], which can be directly calculated through the structural parameters. When it keeps invariant under the reversions of the external magnetic field [Formula: see text] and the dislocation [Formula: see text], or one of them, the spectra are reciprocal. Otherwise, the SW possesses nonreciprocal spectra with direction-dependent band edges and exhibits a directional magnetoresistance effect. This criterion can be regarded as a necessary and sufficient condition for the (non)reciprocity in the spin lattice. Besides, this novel lattice provides a prototype for spin diodes and spin logic gates.
Nonreciprocal spin wave elementary excitation in dislocated dimerized Heisenberg chains
NASA Astrophysics Data System (ADS)
Liu, Wanguo; Shen, Yang; Fang, Guisheng; Jin, Chongjun
2016-05-01
A mechanism for realizing nonreciprocal elementary excitation of spin wave (SW) is proposed. We study a reference model which describes a magnonic crystal (MC) formed by two Heisenberg chains with a lateral displacement (dislocation) and a longitudinal spacer, and derive a criterion to judge whether the elementary excitation spectra are reciprocal in this ferromagnetic lattice. An analytical method based on the spin precession equation is used to solve the elementary excitation spectra. The solution is related to a key factor, the spatio-temporal structure factor {θk}≤ft(Δ x,B\\right) , which can be directly calculated through the structural parameters. When it keeps invariant under the reversions of the external magnetic field B and the dislocation Δ x , or one of them, the spectra are reciprocal. Otherwise, the SW possesses nonreciprocal spectra with direction-dependent band edges and exhibits a directional magnetoresistance effect. This criterion can be regarded as a necessary and sufficient condition for the (non)reciprocity in the spin lattice. Besides, this novel lattice provides a prototype for spin diodes and spin logic gates.
NASA Astrophysics Data System (ADS)
Onoda, Masashige; Ikeda, Satoshi
2013-05-01
The crystal structure and electronic properties of the triclinic LixVOPO4 insertion electrode system with 0.9≤ x ≤ 1 are explored through measurements of x-ray four-circle diffraction, magnetization, and electron paramagnetic resonance. For x = 0.95 at 295 K, the one-dimensional corner-sharing chain of distorted VO6 octahedra has the alternating V--V distances of 3.5986 and 3.6219 Å with mixed-valence states of V4+ and V5+. All of the compositions exhibit a one-dimensional paramagnetism at temperatures above Tc1 ≃ 15 K due to the compensation from V--O--V bond angles in spite of the bond alternation. They have a long-range order to spin-singlet states at Tc2 ≃ 10 K due to the alternating-exchange couplings, accompanied by spin-dimer fluctuations between Tc1 and Tc2.
Proton NMR study of spin dynamics in the magnetic organic chains M (hfac)3 NITEt (M =Eu3 +,Gd3 + )
NASA Astrophysics Data System (ADS)
Mariani, M.; Lascialfari, A.; Caneschi, A.; Ammannato, L.; Gatteschi, D.; Rettori, A.; Pini, M. G.; Cucci, C.; Borsa, F.
2016-04-01
In this work, we present a nuclear magnetic resonance (NMR) study of the spin dynamics in the rare-earth-based low-dimensional molecular magnetic chains Eu (hfac) 3NITEt and Gd (hfac) 3NITEt (in short, Eu-Et and Gd-Et). Although both samples are based on the same chemical building block, [(hfac) 3NITEt ] , their magnetic properties change dramatically when the Eu3 + ion, which is nonmagnetic at low temperatures, is substituted by the magnetic Gd3 + ion. The present proton NMR investigation shows that, down to the lowest investigated temperature (T =1.5 K for Gd-Et and T =3 K for Eu-Et), the Eu-Et chain behaves as a one-dimensional Heisenberg model with antiferromagnetic exchange coupling (J =-20 K) between s =1 /2 organic radicals, and has a T -independent exchange frequency (ωe=2.6 ×1012 rad/s). In the Gd-Et chain, in contrast, a competition arises between nearest-neighbor ferromagnetic coupling and next-nearest-neighbor antiferromagnetic coupling; moreover, two phase transitions have previously been found, in agreement with Villain's conjecture: a first transition, at T0=2.2 K, from a high temperature paramagnetic phase to a chiral spin liquid phase, and a second transition, at TN=1.9 K, to a three-dimensional helical spin solid phase. Contrary to the Eu-Et chain (whose three-dimensional ordering temperature is estimated to insurge at very low, TN≈0.3 K), critical spin dynamics effects have been measured in the Gd-Et chain on approaching TN=1.9 K: namely, a divergence of the proton nuclear spin-lattice relaxation rate 1 /T1 , which in turn produces a sudden wipe-out of the NMR signal in a very narrow (Δ T ˜0.04 K) temperature range above TN. Below TN, an inhomogeneous broadening of the NMR line indicates a complete spin freezing. At T0=2.2 K, instead, such critical effects are not observed because NMR measurements probe the two-spin correlation function, while the chiral spin liquid phase transition is associated with a divergence of the four-spin
Solitons in a one-dimensional Wigner crystal
Pustilnik, M.; Matveev, K. A.
2015-04-16
In one-dimensional quantum systems with strong long-range repulsion particles arrange in a quasi-periodic chain, the Wigner crystal. Here, we demonstrate that besides the familiar phonons, such one-dimensional Wigner crystal supports an additional mode of elementary excitations, which can be identified with solitons in the classical limit. Furthermore, we compute the corresponding excitation spectrum and argue that the solitons have a parametrically small decay rate at low energies. Finally, we discuss implications of our results for the behavior of the dynamic structure factor.
Dynamics of hot random quantum spin chains: from anyons to Heisenberg spins
NASA Astrophysics Data System (ADS)
Parameswaran, Siddharth; Potter, Andrew; Vasseur, Romain
2015-03-01
We argue that the dynamics of the random-bond Heisenberg spin chain are ergodic at infinite temperature, in contrast to the many-body localized behavior seen in its random-field counterpart. First, we show that excited-state real-space renormalization group (RSRG-X) techniques suffer from a fatal breakdown of perturbation theory due to the proliferation of large effective spins that grow without bound. We repair this problem by deforming the SU (2) symmetry of the Heisenberg chain to its `anyonic' version, SU(2)k , where the growth of effective spins is truncated at spin S = k / 2 . This enables us to construct a self-consistent RSRG-X scheme that is particularly simple at infinite temperature. Solving the flow equations, we compute the excited-state entanglement and show that it crosses over from volume-law to logarithmic scaling at a length scale ξk ~eαk3 . This reveals that (a) anyon chains have random-singlet-like excited states for any finite k; and (b) ergodicity is restored in the Heisenberg limit k --> ∞ . We acknowledge support from the Quantum Materials program of LBNL (RV), the Gordon and Betty Moore Foundation (ACP), and UC Irvine startup funds (SAP).
The spin Sutherland model of D type and its associated spin chain
NASA Astrophysics Data System (ADS)
Basu-Mallick, B.; Finkel, F.; González-López, A.
2011-02-01
In this paper we study the su(m) spin Sutherland (trigonometric) model of D type and its related spin chain of Haldane-Shastry type obtained by means of Polychronakos's freezing trick. As in the rational case recently studied by the authors, we show that these are new models, whose properties cannot be simply deduced from those of their well-known BC counterparts by taking a suitable limit. We identify the Weyl-invariant extended configuration space of the spin dynamical model, which turns out to be the N-dimensional generalization of a rhombic dodecahedron. This is in fact one of the reasons underlying the greater complexity of the models studied in this paper in comparison with both their rational and BC counterparts. By constructing a non-orthogonal basis of the Hilbert space of the spin dynamical model on which its Hamiltonian acts triangularly, we compute its spectrum in closed form. Using this result and applying the freezing trick, we derive an exact expression for the partition function of the associated Haldane-Shastry spin chain of D type.
Bartucci, R; Gambacorta, A; Gliozzi, A; Marsh, D; Sportelli, L
2005-11-15
Membranes of thermophilic Archaea are composed of unique tetraether lipids in which C40, saturated, methyl-branched biphytanyl chains are linked at both ends to polar groups. In this paper, membranes composed of bipolar lipids P2 extracted from the acidothermophile archaeon Sulfolobus solfataricus are studied. The biophysical basis for the membrane formation and thermal stability is investigated by using electron spin resonance (ESR) of spin-labeled lipids. Spectral anisotropy and isotropic hyperfine couplings are used to determine the chain flexibility and polarity gradients, respectively. For comparison, similar measurements have been carried out on aqueous dispersions of diacyl reference lipid dipalmitoyl phosphatidylcholine and also of diphytanoyl phosphatidylcholine, which has methyl-branched chains. At a given temperature, the bolaform lipid chains are more ordered and less flexible than in normal bilayer membranes. Only at elevated temperatures (80 degrees C) does the flexibility of the chain environment in tetraether lipid assemblies approach that of fluid bilayer membranes. The height of the hydrophobic barrier formed by a monolayer of archaebacterial lipids is similar to that in conventional fluid bilayer membranes, and the permeability barrier width is comparable to that formed by a bilayer of C16 lipid chains. At a mole ratio of 1:2, the tetraether P2 lipids mix well with dipalmitoyl phosphatidylcholine lipids and stabilize conventional bilayer membranes. The biological as well as the biotechnological relevance of the results is discussed.
Electron spin resonance shifts in S=1 antiferromagnetic chains
NASA Astrophysics Data System (ADS)
Furuya, Shunsuke C.; Maeda, Yoshitaka; Oshikawa, Masaki
2013-03-01
We discuss electron spin resonance (ESR) shifts in spin-1 Heisenberg antiferromagnetic chains with a weak single-ion anisotropy, based on several effective field theories: the O(3) nonlinear sigma model (NLSM) in the Haldane phase, free-fermion theories around the lower and the upper critical fields. In the O(3) NLSM, the single-ion anisotropy corresponds to a composite operator which creates two magnons at the same time and position. Therefore, even inside a parameter range where free magnon approximation is valid for thermodynamics, we have to take interactions among magnons into account in order to include the single-ion anisotropy as a perturbation. Although the O(3) NLSM is only valid in the Haldane phase, an appropriate translation of Faddeev-Zamolodchikov operators of the O(3) NLSM to fermion operators enables one to treat ESR shifts near the lower critical field in a similar manner to discussions in the Haldane phase. Our theory gives quantitative agreements with a numerical evaluation using quantum Monte Carlo simulation, and also with recent ESR experimental results on a spin-1 chain compound Ni(C5H14N2)2N3(PF6).
Absence of diffusion in disordered spin-chains
NASA Astrophysics Data System (ADS)
Gazit, Snir; Khait, Ilia; Yao, Norman; Auerbach, Assa
We study the dynamical properties of the one dimensional XXZ model at infinite temperature in the presence of quench disorder. This model is expected to exhibit a many body localization (MBL) transition at finite disorder. We compute the local dynamical spin correlation function using a non-perturbative continued fraction expansion. The expansion up to 15th order is sufficient to achieve convergence of our extrapolation scheme. We compare the continued fraction result to the exact diagonalization (ED) on 22 sites. The phase diagram is determined in the disorder-anisotropy plane. Our main finding is the emergence of sub-diffusive transport and absence of a diffusive behavior (ω - 1 / 2 at low frequencies) in the weak disorder regime. The lack of a true diffusive phase contrasts with previous results and expectations obtained from smaller system sizes. In addition, the MBL transition is determined to occur at lower values than those deduced by ED on finite systems. Lastly, the finite frequency-momentum dynamical structure factor is computed and we explore its space-time scaling behavior.
Multipolar phase in frustrated spin-1/2 and spin-1 chains
NASA Astrophysics Data System (ADS)
Parvej, Aslam; Kumar, Manoranjan
2017-08-01
The J1-J2 spin-chain model with nearest-neighbor J1 and next-nearest-neighbor antiferromagnetic J2 interaction is one of the most popular frustrated magnetic models. This model system has been extensively studied theoretically and applied to explain the magnetic properties of the real low-dimensional materials. However, the existence of different phases for the J1-J2 model in an axial magnetic field h is either not understood or has been controversial. In this paper, we show the existence of higher order p >4 multipolar phase near the critical point (J2/J1)c=-0.25 . The criterion to detect the quadrupolar or spin nematic (SN)/spin density wave of type two (SDW2) phase using the inelastic neutron scattering (INS) experiment data is also discussed, and INS data of LiCuVO4 compound is modeled. We discuss the dimerized and degenerate ground state in the quadrupolar phase. The major contribution of binding energy in the spin-1/2 system comes from the longitudinal component of the nearest-neighbor bonds. We also study spin nematic /SDW2 phase in spin-1 system in large J2/J1 limit.
Entanglement and corner Hamiltonian spectra of integrable open spin chains
NASA Astrophysics Data System (ADS)
Kim, Panjin; Katsura, Hosho; Trivedi, Nandini; Han, Jung Hoon
2016-11-01
We investigate the entanglement entropy (EE) and entanglement spectra (ES) of critical SU (N ) (2 ≤N ≤4 ) spin chains and other integrable models of finite length with the density matrix renormalization group method. For all models under investigation, we find a remarkable agreement of the level spacings and the degeneracy structure of the ES with the spectrum of the corner Hamiltonian (CS), defined as the generator of the associated corner transfer matrix. The correspondence holds between ES(n ) at the n th cut position from the edge of the spin model, and the spectrum CS(n ) of the corner Hamiltonian of length n , for all values of n that we have checked. The cut position dependence of the ES shows a period-N oscillatory behavior for a given SU (N ) chain, reminiscent of the oscillatory part of the entanglement entropy observed in the past for the same models. However, the oscillations of the ES do not die out in the bulk of the chain, in contrast to the asymptotically vanishing oscillation of the entanglement entropy. We present a heuristic argument based on Young tableaux construction that can explain the period-N structure of the ES qualitatively.
Papp, E.; Micu, C.; Racolta, D.
2013-11-13
In this paper one deals with the theoretical derivation of energy bands and of related wavefunctions characterizing quasi 1D semiconductor heterostructures, such as InAs quantum wire models. Such models get characterized this time by equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions of dimensionless magnitude a under the influence of in-plane magnetic fields of magnitude B. We found that the orientations of the field can be selected by virtue of symmetry requirements. For this purpose one resorts to spin conservations, but alternative conditions providing sensible simplifications of the energy-band formula can be reasonably accounted for. Besides the wavenumber k relying on the 1D electron, one deals with the spin-like s=±1 factors in the front of the square root term of the energy. Having obtained the spinorial wavefunction, opens the way to the derivation of spin precession effects. For this purpose one resorts to the projections of the wavenumber operator on complementary spin states. Such projections are responsible for related displacements proceeding along the Ox-axis. This results in a 2D rotation matrix providing both the precession angle as well as the precession axis.
Low-Temperature Properties of Quasi-One-Dimensional Molecule-Based Ferromagnets
NASA Astrophysics Data System (ADS)
Nakanishi, Takashi; Yamamoto, Shoji; Sakai, Tôru
2001-05-01
Quantum and thermal behaviors of low-dimensional mixed-spin systems are investigated with particular emphasis on the design of molecule-based ferromagnets. One can obtain a molecular ferromagnet by assembling molecular bricks so as to construct a low-dimensional system with a magnetic ground state and then coupling the chains or the layers again in a ferromagnetic fashion. Two of thus-constructed quasi-one-dimensional bimetallic compounds are qualitatively viewed within the spin-wave treatment, one of which successfully grows into a bulk magnet, while the other of which ends in a singlet ground state. Then, concentrating on the ferrimagnetic arrangement on a two-leg ladder which is well indicative of general coupled-chain ferrimagnets, we develop the spin-wave theory and fully reveal its low-energy structure. We inquire further into the ferromagnetic aspect of the ferrimagnetic ladder numerically calculating the sublattice magnetization and the magnetic susceptibility. There exists a moderate coupling strength between the chains in order to obtain the most ferromagnetic ferrimagnet.
Switching of spins and entanglement in surface-supported antiferromagnetic chains.
Sivkov, Ilia N; Bazhanov, Dmitry I; Stepanyuk, Valeri S
2017-06-05
Previous experimental studies discovered universal growth of chains and nanowires of various chemical elements on a corrugated molecular network of Cu3N on the Cu(110). Herein, performing combined ab initio and quantum Hamiltonian studies we demonstrate that such chains can be used for a fast spin switching and entanglement generation by locally applied magnetic pulses. As an example, we show that in antiferromagnetic Co chains a strong entanglement between ends of chains occurs during spin switching. A novel parity effect in spin dynamics is reported. Even-numbered chains are found to exhibit significantly faster spin switching than odd-numbered counterparts. Moreover, at certain parameters of the system the dimerization effect in the spin dynamics of the chains was found. Our studies give a clear evidence that tailoring spin dynamics and entanglement can be achieved by magnetic fields and by tuning exchange interactions in supported chains.
NASA Astrophysics Data System (ADS)
Sadiek, G.
2017-07-01
We consider a finite one-dimensional Ising spin chain under the influence of a dissipative Lindblad environment obeying the Born-Markovian constrain in presence of an external magnetic field with open boundary conditions. We study the effect of a single impurity, located at the terminal or center of the chain, on the time evolution and asymptotic steady state of the bipartite entanglement in the chain starting from a maximally entangled initial state. We found that the impurity has a significant effect on the bipartite entanglement of its nearest spins and can be used to tune their steady state value but has almost no noticeable impact on the far ones. At finite temperature, the thermal excitations suppress the dynamics of the system and reduce the value of the steady state and may completely wipe it out as the temperature is increased, which eliminates the effect of the impurity in that case.
Second virial coefficient of one dimensional gas
Mijatovic, M.
1982-08-01
The second virial coefficient of a one dimensional gas is calculated using the expressions for the scattering amplitude. The scattering amplitude is chosen in the form of rational function of wave vector.
One-Dimensional Czedli-Type Islands
ERIC Educational Resources Information Center
Horvath, Eszter K.; Mader, Attila; Tepavcevic, Andreja
2011-01-01
The notion of an island has surfaced in recent algebra and coding theory research. Discrete versions provide interesting combinatorial problems. This paper presents the one-dimensional case with finitely many heights, a topic convenient for student research.
One-Dimensional Czedli-Type Islands
ERIC Educational Resources Information Center
Horvath, Eszter K.; Mader, Attila; Tepavcevic, Andreja
2011-01-01
The notion of an island has surfaced in recent algebra and coding theory research. Discrete versions provide interesting combinatorial problems. This paper presents the one-dimensional case with finitely many heights, a topic convenient for student research.
NASA Astrophysics Data System (ADS)
De Luca, Andrea; Collura, Mario; De Nardis, Jacopo
2017-07-01
We construct exact steady states of unitary nonequilibrium time evolution in the gapless XXZ spin-1/2 chain where integrability preserves ballistic spin transport at long times. We characterize the quasilocal conserved quantities responsible for this feature and introduce a computationally effective way to evaluate their expectation values on generic matrix product initial states. We employ this approach to reproduce the long-time limit of local observables in all quantum quenches which explicitly break particle-hole or time-reversal symmetry. We focus on a class of initial states supporting persistent spin currents and our predictions remarkably agree with numerical simulations at long times. Furthermore, we propose a protocol for this model where interactions, even when antiferromagnetic, are responsible for the unbounded growth of a macroscopic magnetic domain.
Drude Weight in Non Solvable Quantum Spin Chains
NASA Astrophysics Data System (ADS)
Benfatto, G.; Mastropietro, V.
2011-04-01
For a quantum spin chain or 1D fermionic system, we prove that the Drude weight D verifies the universal Luttinger liquid relation vs2=D/kappa, where κ is the susceptibility and v s is the Fermi velocity. This result is proved by rigorous Renormalization Group methods and is true for any weakly interacting system, regardless its integrability. This paper, combined with Benfatto and Mastropietro (in J. Stat. Phys. 138, 1084-1108, 2010), completes the proof of the Luttinger liquid conjecture for such systems.
The paramagnetic properties of ferromagnetic mixed-spin chain system
NASA Astrophysics Data System (ADS)
Hu, Ai-Yuan; Wu, Zhi-Min; Cui, Yu-Ting; Qin, Guo-Ping
2015-01-01
The double-time Green's function method is used to investigate the paramagnetic properties of ferromagnetic mixed-spin chain system within the random-phase approximation and Anderson-Callen's decoupling approximation. The analytic expressions of the transverse susceptibility, longitudinal susceptibility and correlation length are obtained under transverse and longitudinal magnetic field. Using the analytic expressions of the transverse and longitudinal susceptibility to fit the experimental results, our results well agree with experimental data and the results from the high temperature series expansion within a simple Padé approximation.
Bond operator method of dimerized ferrimagnetic spin chain
NASA Astrophysics Data System (ADS)
Chen, Yuge; Li, Yinxiang; Tian, Lijun; Chen, Bin
2017-09-01
We use bond operator method to study the dimerized ferrimagnetic spin chain. With the dimerization parameter g from 1 to 0, the model describes the system from normal ferrimagnetic state to dimer state. From the energy spectrums, the system energy is changed from ferrimagnetic spectrum to large energy gap at bond state. At finite temperature, the uniform susceptibility, internal energy and specific heat are calculated respectively with different dimerization parameters g. These results qualitatively agree with the numerical results of other methods quite well.
How periodic driving heats a disordered quantum spin chain
NASA Astrophysics Data System (ADS)
Rehn, Jorge; Lazarides, Achilleas; Pollmann, Frank; Moessner, Roderich
2016-07-01
We study the energy absorption in real time of a disordered quantum spin chain subjected to coherent monochromatic periodic driving. We determine characteristic fingerprints of the well-known ergodic (Floquet-Eigenstate thermalization hypothesis for slow driving/weak disorder) and many-body localized (Floquet-many-body localization for fast driving/strong disorder) phases. In addition, we identify an intermediate regime, where the energy density of the system—unlike the entanglement entropy a local and bounded observable—grows logarithmically slowly over a very large time window.
Thermal stability in exchange-spring chains of spins
NASA Astrophysics Data System (ADS)
Pellicelli, Raffaele; Solzi, Massimo
2016-02-01
Thermal stability and switching behaviour have been compared in pure-hard and soft-hard Heisenberg linear spin chains of the same total length and equal magnetic parameters (except for magnetic anisotropy) with the anisotropy axis and external magnetic field parallel to the chain direction. The zero-temperature energy barriers and finite-temperature transition rates between remanent equilibrium states have been calculated by utilizing the string method and the forward flux sampling (FFS) method, respectively. Depending on the assumed interfaces, the FFS method could in fact fail to correctly sample the characteristic transition paths at interfaces at which these paths have probabilities much lower than those associated with other non-characteristic transition paths. This can especially occur in the case of the asymmetric energy landscapes and multiple asymmetric minimum energy paths (MEPs) of soft-hard systems. Therefore, a proper interface definition is needed in order to deduce the correct transition rates. In particular, we show that the thermal switching of soft-hard chains starting in the soft or in the hard part turns out to occur with an equal rate provided that the interfaces of the FFS method are defined on the basis of the corresponding zero-temperature MEPs. The thermal stability of a soft-hard chain in the remanent equilibrium state could be to some extent lower with respect to that of a pure-hard chain, due to the shorter hard-part length crossed by the domain wall formed in the chain and also to the related slightly smaller energy barrier. However, its switching field at zero temperature is verified to be widely lower than that of the pure-hard chain. Analytical expressions of switching fields and energy barriers have been deduced in various cases.
Factorizations of one-dimensional classical systems
Kuru, Senguel; Negro, Javier
2008-02-15
A class of one-dimensional classical systems is characterized from an algebraic point of view. The Hamiltonians of these systems are factorized in terms of two functions that together with the Hamiltonian itself close a Poisson algebra. These two functions lead directly to two time-dependent integrals of motion from which the phase motions are derived algebraically. The systems so obtained constitute the classical analogues of the well known factorizable one-dimensional quantum mechanical systems.
One dimensional representations in quantum optics
NASA Technical Reports Server (NTRS)
Janszky, J.; Adam, P.; Foldesi, I.; Vinogradov, An. V.
1993-01-01
The possibility of representing the quantum states of a harmonic oscillator not on the whole alpha-plane but on its one dimensional manifolds is considered. It is shown that a simple Gaussian distribution along a straight line describes a quadrature squeezed state while a similar Gaussian distribution along a circle leads to the amplitude squeezed state. The connection between the one dimensional representations and the usual Glauber representation is discussed.
Low-energy properties of aperiodic quantum spin chains.
Vieira, André P
2005-02-25
We investigate the low-energy properties of antiferromagnetic quantum XXZ spin chains with couplings following two-letter aperiodic sequences, by an adaptation of the Ma-Dasgupta-Hu renormalization-group method. For a given aperiodic sequence, we argue that, in the easy-plane anisotropy regime, intermediate between the XX and Heisenberg limits, the general scaling form of the thermodynamic properties is essentially given by the exactly known XX behavior, providing a classification of the effects of aperiodicity on XXZ chains. As representative illustrations, we present analytical and numerical results for the low-temperature thermodynamics and the ground-state correlations for couplings following the Fibonacci quasiperiodic structure and a binary Rudin-Shapiro sequence, whose geometrical fluctuations are similar to those induced by randomness.
"Light-cone" dynamics after quantum quenches in spin chains.
Bonnes, Lars; Essler, Fabian H L; Läuchli, Andreas M
2014-10-31
Signal propagation in the nonequilibrium evolution after quantum quenches has recently attracted much experimental and theoretical interest. A key question arising in this context is what principles, and which of the properties of the quench, determine the characteristic propagation velocity. Here we investigate such issues for a class of quench protocols in one of the central paradigms of interacting many-particle quantum systems, the spin-1/2 Heisenberg XXZ chain. We consider quenches from a variety of initial thermal density matrices to the same final Hamiltonian using matrix product state methods. The spreading velocities are observed to vary substantially with the initial density matrix. However, we achieve a striking data collapse when the spreading velocity is considered to be a function of the excess energy. Using the fact that the XXZ chain is integrable, we present an explanation of the observed velocities in terms of "excitations" in an appropriately defined generalized Gibbs ensemble.
Qubit teleportation and transfer across antiferromagnetic spin chains.
Campos Venuti, L; Degli Esposti Boschi, C; Roncaglia, M
2007-08-10
We explore the capability of spin-1/2 chains to act as quantum channels for both teleportation and transfer of qubits. Exploiting the emergence of long-distance entanglement in low-dimensional systems [Phys. Rev. Lett. 96, 247206 (2006)10.1103/Phys.Rev.Lett.96, 247206(2006)], here we show how to obtain high communication fidelities between distant parties. An investigation of protocols of teleportation and state transfer is presented, in the realistic situation where temperature is included. Basing our setup on antiferromagnetic rotationally invariant systems, both protocols are represented by pure depolarizing channels. We propose a scheme where channel fidelity close to 1 can be achieved on very long chains at moderately small temperature.
Low-Energy Properties of Aperiodic Quantum Spin Chains
NASA Astrophysics Data System (ADS)
Vieira, André P.
2005-02-01
We investigate the low-energy properties of antiferromagnetic quantum XXZ spin chains with couplings following two-letter aperiodic sequences, by an adaptation of the Ma-Dasgupta-Hu renormalization-group method. For a given aperiodic sequence, we argue that, in the easy-plane anisotropy regime, intermediate between the XX and Heisenberg limits, the general scaling form of the thermodynamic properties is essentially given by the exactly known XX behavior, providing a classification of the effects of aperiodicity on XXZ chains. As representative illustrations, we present analytical and numerical results for the low-temperature thermodynamics and the ground-state correlations for couplings following the Fibonacci quasiperiodic structure and a binary Rudin-Shapiro sequence, whose geometrical fluctuations are similar to those induced by randomness.
All exactly solvable U(1)-invariant quantum spin 1 chains from Hecke algebra
Alcarez, F.C. ); Koberle, R. ); Lima-Santos, A. )
1992-12-10
In this paper, the authors obtain all exactly integrable spin 1 quantum chains, which are U(1) invariant and satisfy the Hecke algebra. The authors present various generalizations for arbitrary spin S and discuss their solution via Bethe ansatz methods.
Clérac, Rodolphe; Miyasaka, Hitoshi; Yamashita, Masahiro; Coulon, Claude
2002-10-30
. This result indicates the presence of a metastable state without magnetic long-range order. This material is the first experimental design of a heterometallic chain with ST = 3 magnetic units showing a "single-chain magnet" behavior predicted in 1963 by R. J. Glauber for an Ising one-dimensional system. This work opens new perspectives for one-dimensional systems to obtain high temperature metastable magnets by combining high spin magnetic units, strong interunit interactions, and uniaxial anisotropy.
Chain-based order and quantum spin liquids in dipolar spin ice
NASA Astrophysics Data System (ADS)
McClarty, P. A.; Sikora, O.; Moessner, R.; Penc, K.; Pollmann, F.; Shannon, N.
2015-09-01
Recent experiments on the spin-ice material Dy2Ti2O7 suggest that the Pauling "ice entropy," characteristic of its classical Coulombic spin-liquid state, may be lost at low temperatures [Pomaranski et al., Nat. Phys. 9, 353 (2013), 10.1038/nphys2591]. However, despite nearly two decades of intensive study, the nature of the equilibrium ground state of spin ice remains uncertain. Here we explore how long-range dipolar interactions D , short-range exchange interactions, and quantum fluctuations combine to determine the ground state of dipolar spin ice. We identify the organizational principle that ordered ground states are selected from a set of "chain states" in which dipolar interactions are exponentially screened. Using both quantum and classical Monte Carlo simulation, we establish phase diagrams as a function of quantum tunneling g and temperature T , and find that only a very small gc≪D is needed to stabilize a quantum spin liquid ground state. We discuss the implications of these results for Dy2Ti2O7 .
NASA Astrophysics Data System (ADS)
Casas, Brian; Lampen, Paula; Phan, Manh-Huong; Srikanth, Hariharan; Kovak, Jozef; Skorvanek, Ivan
2015-03-01
The spin chain compound Ca3Co2O6 has been extensively studied due to a number of unusual properties originating from geometrically frustrated Ising-like spin chains arranged in a triangular lattice. These quasi one dimensional structures provide an ideal environment to study dilute magnetic disorder in spin-glass like systems. Disorder controlled via chemical doping has been observed to weaken the spin glass behavior and disrupt a number of metamagnetic transitions found in pristine Ca3Co2O6. We report a systematic study of the effects of dilute Mn doping (x = 0.05 - 0.50) in Ca3Co2-xMnxO6 synthesized via a sol-gel method. Detailed AC and DC magnetization measurements performed on a SQUID magnetometer reveal the suppression of the step-like metamagnetic transitions by a doping of x = 0.25. The relaxation time is found to decrease with increasing Mn content, showing the destruction of the spin-glass like behavior. Our observations yield new insight into the role of site disorder on the glassy behavior in spin chain systems. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-FG02-07ER46438.
Inverse participation ratios in the XX spin chain
NASA Astrophysics Data System (ADS)
Tsukerman, Emmanuel
2017-03-01
We continue the study of the inverse participation ratios (IPRs) of the XXZ Heisenberg spin chain initiated by Stéphan, Furukawa, Misguich, and Pasquier (2009) and continued by Misguich, Pasquier, and Luck (2016) by focusing on the case of the XX Heisenberg spin chain. For the ground state, Stéphan et al. note that calculating the IPR is equivalent to Dyson's constant term ex-conjecture. We express the IPRs of excited states as an apparently new "discrete" Hall inner product. We analyze this inner product using the theory of symmetric functions (Jack polynomials, Schur polynomials, the standard Hall inner product, and ωq ,t) to determine some exact expressions and asymptotics for IPRs. We show that IPRs can be indexed by partitions, and asymptotically the IPR of a partition is equal to that of the conjugate partition. We relate the IPRs to two other models from physics, namely, the circular symplectic ensemble of Dyson and the Dyson-Gaudin two-dimensional Coulomb lattice gas. Finally, we provide a description of the IPRs in terms of a signed count of diagonals of permutohedra.
Mendoza-Arenas, J J; Clark, S R; Jaksch, D
2015-04-01
In this work we analyze the simultaneous emergence of diffusive energy transport and local thermalization in a nonequilibrium one-dimensional quantum system, as a result of integrability breaking. Specifically, we discuss the local properties of the steady state induced by thermal boundary driving in a XXZ spin chain with staggered magnetic field. By means of efficient large-scale matrix product simulations of the equation of motion of the system, we calculate its steady state in the long-time limit. We start by discussing the energy transport supported by the system, finding it to be ballistic in the integrable limit and diffusive when the staggered field is finite. Subsequently, we examine the reduced density operators of neighboring sites and find that for large systems they are well approximated by local thermal states of the underlying Hamiltonian in the nonintegrable regime, even for weak staggered fields. In the integrable limit, on the other hand, this behavior is lost, and the identification of local temperatures is no longer possible. Our results agree with the intuitive connection between energy diffusion and thermalization.
NASA Astrophysics Data System (ADS)
Pchelkina, Z. V.; Solovyev, I. V.
2015-01-01
The effects of orbital degrees of freedom on the exchange interactions in a quasi-one-dimensional spin-1 antiferromagnet CaV2O4 are systematically studied. For this purpose a realistic low-energy electron model with the parameters derived from the first-principles calculations is constructed in the Wannier basis for the t2g bands. The exchange interactions are calculated using both the theory of infinitesimal spin rotations near the mean-field ground state and the superexchange model, which provide a consistent description. The obtained behaviour of exchange interactions differs substantially from the previously proposed phenomenological picture based on magnetic measurements and structural considerations, namely: (i) despite the quasi-one-dimensional character of the crystal structure, consisting of the zigzag chains of the edge-sharing VO6 octahedra, the electronic structure is essentially three-dimensional, that leads to finite interactions between the chains; (ii) the exchange interactions along the legs of the chains appear to dominate; and (iii) there is a substantial difference in exchange interactions in two crystallographically inequivalent chains. The combination of these three factors successfully reproduces the behaviour of experimental magnetic susceptibility.
NASA Astrophysics Data System (ADS)
De La Rosa Gomez, Alejandro; MacKay, Niall; Regelskis, Vidas
2017-04-01
We present a general method of folding an integrable spin chain, defined on a line, to obtain an integrable open spin chain, defined on a half-line. We illustrate our method through two fundamental models with sl2 Lie algebra symmetry: the Heisenberg XXX and the Inozemtsev hyperbolic spin chains. We obtain new long-range boundary Hamiltonians and demonstrate that they exhibit Yangian symmetries, thus ensuring integrability of the models we obtain. The method presented provides a ;bottom-up; approach for constructing integrable boundaries and can be applied to any spin chain model.
Defects in a nonlinear pseudo one-dimensional solid
NASA Astrophysics Data System (ADS)
Blanchet, Graciela B.; Fincher, C. R., Jr.
1985-03-01
These infrared studies of acetanilide together with the existence of two equivalent structures for the hydrogen-bonded chain suggest the possibility of a topological defect state rather than a Davydov soliton as suggested previously. Acetanilide is an example of a class of one-dimensional materials where solitons are a consequence of a twofold degenerate structure and the nonlinear dynamics of the hydrogen-bonded network.
One-dimensional Gromov minimal filling problem
NASA Astrophysics Data System (ADS)
Ivanov, Alexandr O.; Tuzhilin, Alexey A.
2012-05-01
The paper is devoted to a new branch in the theory of one-dimensional variational problems with branching extremals, the investigation of one-dimensional minimal fillings introduced by the authors. On the one hand, this problem is a one-dimensional version of a generalization of Gromov's minimal fillings problem to the case of stratified manifolds. On the other hand, this problem is interesting in itself and also can be considered as a generalization of another classical problem, the Steiner problem on the construction of a shortest network connecting a given set of terminals. Besides the statement of the problem, we discuss several properties of the minimal fillings and state several conjectures. Bibliography: 38 titles.
Interacting Electrons in Quasi-One-Dimensional Organic Superconductors
NASA Astrophysics Data System (ADS)
Bourbonnais, C.; Jérome, D.
This review highlights the main features of the temperature-pressure phase diagram of the Bechgaard and Fabre salts series of quasi-one-dimensional organic superconductors. We go over the various electronic and structural instabilities found experimentally in the normal state of the sulfur (TMTTF)2X series at relatively high temperature and show how these are strongly influenced by the one-dimensional character of electronic degrees of freedom. The problem of three-dimensional long-range order is then discussed for the Fabre series and the mechanisms responsible for the spin-Peierls and Néel phase transitions are depicted. The influence of pressure on the relative stability of these phases and the emergence of quasi-particles when the Fabre series evolves towards the Bechgaard (TMTSF)2X salts series are presented. Itinerant antiferromagnetism, density-wave and uncoventional superconductivity are described and the microscopic origin of their interplay is! discussed.
Boosted one dimensional fermionic superfluids on a lattice
NASA Astrophysics Data System (ADS)
Ray, Sayonee; Mukerjee, Subroto; Shenoy, Vijay B.
2017-09-01
We study the effect of a boost (Fermi sea displaced by a finite momentum) on one dimensional systems of lattice fermions with short-ranged interactions. In the absence of a boost such systems with attractive interactions possess algebraic superconducting order. Motivated by physics in higher dimensions, one might naively expect a boost to weaken and ultimately destroy superconductivity. However, we show that for one dimensional systems the effect of the boost can be to strengthen the algebraic superconducting order by making correlation functions fall off more slowly with distance. This phenomenon can manifest in interesting ways, for example, a boost can produce a Luther-Emery phase in a system with both charge and spin gaps by engendering the destruction of the former.
Magnons in one-dimensional k-component Fibonacci structures
NASA Astrophysics Data System (ADS)
Costa, C. H.; Vasconcelos, M. S.
2014-05-01
We have studied the magnon transmission through of one-dimensional magnonic k-component Fibonacci structures, where k different materials are arranged in accordance with the following substitution rule: Sn(k)=Sn-1(k)Sn-k(k) (n ≥k=0,1,2,…), where Sn(k) is the nth stage of the sequence. The calculations were carried out in exchange dominated regime within the framework of the Heisenberg model and taking into account the RPA approximation. We have considered multilayers composed of simple cubic spin-S Heisenberg ferromagnets, and, by using the powerful transfer-matrix method, the spin wave transmission is obtained. It is demonstrated that the transmission coefficient has a rich and interesting magnonic pass- and stop-bands structures, which depends on the frequency of magnons and the k values.
Magnons in one-dimensional k-component Fibonacci structures
Costa, C. H.; Vasconcelos, M. S.
2014-05-07
We have studied the magnon transmission through of one-dimensional magnonic k-component Fibonacci structures, where k different materials are arranged in accordance with the following substitution rule: S{sub n}{sup (k)}=S{sub n−1}{sup (k)}S{sub n−k}{sup (k)} (n≥k=0,1,2,…), where S{sub n}{sup (k)} is the nth stage of the sequence. The calculations were carried out in exchange dominated regime within the framework of the Heisenberg model and taking into account the RPA approximation. We have considered multilayers composed of simple cubic spin-S Heisenberg ferromagnets, and, by using the powerful transfer-matrix method, the spin wave transmission is obtained. It is demonstrated that the transmission coefficient has a rich and interesting magnonic pass- and stop-bands structures, which depends on the frequency of magnons and the k values.
Entanglement between random and clean quantum spin chains
NASA Astrophysics Data System (ADS)
Juhász, Róbert; Kovács, István A.; Roósz, Gergő; Iglói, Ferenc
2017-08-01
The entanglement entropy in clean, as well as in random quantum spin chains has a logarithmic size-dependence at the critical point. Here, we study the entanglement of composite systems that consist of a clean subsystem and a random subsystem, both being critical. In the composite, antiferromagnetic XX-chain with a sharp interface, the entropy is found to grow in a double-logarithmic fashion {{ S}}∼ \\ln\\ln(L) , where L is the length of the chain. We have also considered an extended defect at the interface, where the disorder penetrates into the homogeneous region in such a way that the strength of disorder decays with the distance l from the contact point as ∼l-κ . For κ<1/2 , the entropy scales as {{ S}}(κ) ≃ \\frac{\\ln 2 (1-2κ)}{6}{\\ln L} , while for κ ≥slant 1/2 , when the extended interface defect is an irrelevant perturbation, we recover the double-logarithmic scaling. These results are explained through strong-disorder RG arguments.
Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M.; ...
2015-02-01
Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstancesmore » be regarded as more complex than the physics of a spin-orbital chain.« less
Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M. ; Devereaux, T. P.
2015-02-01
Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstances be regarded as more complex than the physics of a spin-orbital chain.
Excitation spectra of generalized antiferromagnetic Heisenberg spin chains (abstract)
NASA Astrophysics Data System (ADS)
Parkinson, J. B.; Bonner, J. C.
1988-04-01
We compare the excitation spectra in the presence of a magnetic field of a number of integrable (exactly solvable) and nonintegrable quantum spin chains of various spin value s. The archetypal Bethe-ansatz integrable model is the s= 1/2 Heisenberg antiferromagnet (HB AFM). The excitation spectra are characterized by a soft mode which tracks across the Brillouin zone as the field increases to its saturation value. A class of Bethe-ansatz integrable models with SU(2) symmetry and the general spin s display excitation spectra qualitatively similar to the spin- 1/2 model above, for all s. A second class of Bethe-ansatz integrable models has SU(n) symmetry, where n=2s+1. Like the SU(2) integrable chains, these models have gapless excitation spectra, but the basic Brillouin zone changes from k=±2π/(2s+1)a. Studies show that periodicity of the SU(3) member of the class changes (increases) as the field increases to saturation. For both classes of integrable models, there is a single type of excitation pattern which is generically similar for all s. In the case of the other models, on the other hand, numerical studies show that the excitations divide into at least two distinct classes. In the case of the s=1 HB AFM, at high fields (corresponding to SzT=N,N-1, . . .,N/2) the excitations map approximately onto the complete set of excitations for s= 1/2 , whereas at low fields (SzT=N/2,N/2-1,. . .,0) the excitations have notable classical character. In the case of the s=1 model with pure biquadratic exchange, one set of excitations, corresponding to SzT even (SzT=N,N-2,. . .,2,0), again shows an approximate mapping to the complete excitation set for s= 1/2 . The second class of excitations, corresponding to SzT odd, are very different. They are symmetric about k=±π/2a for all SzT, i.e., correspond to a basic Brillouin zone of ±π/2a.
Entanglement in a time-dependent coupled XY spin chain in an external magnetic field
Sadiek, Gehad; Alkurtass, Bedoor; Aldossary, Omar
2010-11-15
We consider an infinite one-dimensional anisotropic XY spin chain with a nearest-neighbor time-dependent Heisenberg coupling J(t) between the spins in presence of a time-dependent magnetic field h(t). We discuss a general solution for the system and present an exact solution for particular choice of J and h of practical interest. We investigate the dynamics of entanglement for different degrees of anisotropy of the system and at both zero and finite temperatures. We find that the time evolution of entanglement in the system shows nonergodic and critical behavior at zero and finite temperatures and different degrees of anisotropy. The asymptotic behavior of entanglement at the infinite time limit at zero temperature and constant J and h depends only the parameter {lambda}=J/h rather than the individual values of J and h for all degrees of anisotropy but changes for nonzero temperature. Furthermore, the asymptotic behavior is very sensitive to the initial values of J and h and for particular choices we may create finite asymptotic entanglement regardless of the final values of J and h. The persistence of quantum effects in the system as it evolves and as the temperature is raised is studied by monitoring the entanglement. We find that the quantum effects dominate within certain regions of the kT-{lambda} space that vary significantly depending on the degree of the anisotropy of the system. Particularly, the quantum effects in the Ising model case persist in the vicinity of both its critical phase transition point and zero temperature as it evolves in time. Moreover, the interplay between the different system parameters to tune and control the entanglement evolution is explored.
Finite-Temperature Spin Dynamics in a Perturbed Quantum Critical Ising Chain with an E8 Symmetry
NASA Astrophysics Data System (ADS)
Wu, Jianda; Kormos, Márton; Si, Qimiao
2014-12-01
A spectrum exhibiting E8 symmetry is expected to arise when a small longitudinal field is introduced in the transverse-field Ising chain at its quantum critical point. Evidence for this spectrum has recently come from neutron scattering measurements in cobalt niobate, a quasi-one-dimensional Ising ferromagnet. Unlike its zero-temperature counterpart, the finite-temperature dynamics of the model has not yet been determined. We study the dynamical spin structure factor of the model at low frequencies and nonzero temperatures, using the form factor method. Its frequency dependence is singular, but differs from the diffusion form. The temperature dependence of the nuclear magnetic resonance (NMR) relaxation rate has an activated form, whose prefactor we also determine. We propose NMR experiments as a means to further test the applicability of the E8 description for CoNb2O6 .
Spinning Strings and Integrable Spin Chains in the AdS/CFT Correspondence
NASA Astrophysics Data System (ADS)
Plefka, Jan
2005-12-01
In this introductory review we discuss dynamical tests of the AdS 5 × S 5 string/{mathcal N}=4 Super Yang-Mills duality. After a brief introduction to AdS/CFT, we argue that semiclassical string energies yield information on the quantum spectrum of the string in the limit of large angular momenta on the S 5. The energies of the folded and circular spinning string solutions rotating on a S 3 within the S 5 are derived, which yield all-loop predictions for the dual gauge theory scaling dimensions. These follow from the eigenvalues of the dilatation operator of {mathcal N}=4 Super Yang-Mills in a minimal SU(2) subsector, and we display its reformulation in terms of a Heisenberg s = 1/2 spin chain along with the coordinate Bethe ansatz for its explicit diagonalization. In order to make contact to the spinning string energies, we then study the thermodynamic limit of the one-loop gauge theory Bethe equations and demonstrate the matching with the folded and closed string result at this loop order. Finally, the known gauge theory results at higher-loop orders are reviewed and the associated long-range spin chain Bethe ansatz is introduced, leading to an asymptotic all-loop conjecture for the gauge theory Bethe equations. This uncovers discrepancies at the three-loop order between gauge theory scaling dimensions and string theory energies and the implications of this are discussed. Along the way, we comment on further developments and generalizations of the subject and point to the relevant literature.
Takaishi, Shinya; Tobu, Yasuhiro; Kitagawa, Hiroshi; Goto, Atsushi; Shimizu, Tadashi; Okubo, Takashi; Mitani, Tadaoki; Ikeda, Ryuichi
2004-02-18
81Br Nuclear quadrupole resonance (NQR) measurement was performed in an S = 1/2 one-dimensional Heisenberg antiferromagnetic metal complex [NiBr(chxn)2]Br2 (chxn: 1R,2R-diaminocyclohexane), having a halogen-bridged MX chain structure -Br-Ni3+-Br-Ni3+-Br-. Two 81Br NQR signals were observed below 40 K, while a single signal was observed above 130 K, showing the presence of two nonequivalent bridging Br sites below 40 K. This NQR result together with previously reported magnetic susceptibility and X-ray results indicate the occurrence of a transition into a spin-Peierls state between 40 and 130 K. This communication reports the first spin-Peierls transition in metal complexes in which pure d electrons contribute to the magnetism. In addition, we demonstrated a new experimental method for studying a spin-Peierls system.
Field-driven quantum phase transitions in S =1/2 spin chains
NASA Astrophysics Data System (ADS)
Iaizzi, Adam; Damle, Kedar; Sandvik, Anders W.
2017-05-01
We study the magnetization process of a one-dimensional extended Heisenberg model, the J -Q model, as a function of an external magnetic field h . In this model, J represents the traditional antiferromagnetic Heisenberg exchange and Q is the strength of a competing four-spin interaction. Without external field, this system hosts a twofold-degenerate dimerized (valence-bond solid) state above a critical value qc≈0.85 where q ≡Q /J . The dimer order is destroyed and replaced by a partially polarized translationally invariant state at a critical field value. We find magnetization jumps (metamagnetism) between the partially polarized and fully polarized state for q >qmin , where we have calculated qmin=2/9 exactly. For q >qmin , two magnons (flipped spins on a fully polarized background) attract and form a bound state. Quantum Monte Carlo studies confirm that the bound state corresponds to the first step of an instability leading to a finite magnetization jump for q >qmin . Our results show that neither geometric frustration nor spin anisotropy are necessary conditions for metamagnetism. Working in the two-magnon subspace, we also find evidence pointing to the existence of metamagnetism in the unfrustrated J1-J2 chain (J1>0 ,J2<0 ), but only if J2 is spin anisotropic. In addition to the studies at zero temperature, we also investigate quantum-critical scaling near the transition into the fully polarized state for q ≤qmin at T >0 . While the expected "zero-scale-factor" universality is clearly seen for q =0 and q ≪qmin , for q closer to qmin we find that extremely low temperatures are required to observe the asymptotic behavior, due to the influence of the tricritical point at qmin. In the low-energy theory, one can expect the quartic nonlinearity to vanish at qmin and a marginal sixth-order term should govern the scaling, which leads to a crossover at a temperature T*(q ) between logarithmic tricritical scaling and zero-scale-factor universality, with T*(q )
One-Dimensional Wavefront Sensor Analysis
Neal, Daniel R.
1996-04-25
This software analyzes one-dimensional wavefront sensor data acquired with any of several data acquisition systems. It analyzes the data to determine centroids, wavefront slopes and overall wavefront error. The data can be displayed in many formats, with plots of various parameters vs time and position, including computer generated movies. Data can also be exported for use by other programs.
One-Dimensional Oscillator in a Box
ERIC Educational Resources Information Center
Amore, Paolo; Fernandez, Francisco M.
2010-01-01
We discuss a quantum-mechanical model of two particles that interact by means of a harmonic potential and are confined to a one-dimensional box with impenetrable walls. We apply perturbation theory to the cases of different and equal masses and analyse the symmetry of the states in the latter case. We compare the approximate perturbation results…
One-Dimensional Oscillator in a Box
ERIC Educational Resources Information Center
Amore, Paolo; Fernandez, Francisco M.
2010-01-01
We discuss a quantum-mechanical model of two particles that interact by means of a harmonic potential and are confined to a one-dimensional box with impenetrable walls. We apply perturbation theory to the cases of different and equal masses and analyse the symmetry of the states in the latter case. We compare the approximate perturbation results…
One-dimensional differential Hardy inequality.
Kalybay, Aigerim
2017-01-01
We establish necessary and sufficient conditions for the one-dimensional differential Hardy inequality to hold, including the overdetermined case. The solution is given in terms different from those of the known results. Moreover, the least constant for this inequality is estimated.
One-Dimensional Fluids with Positive Potentials
NASA Astrophysics Data System (ADS)
Fantoni, Riccardo
2017-03-01
We study a class of one-dimensional classical fluids with penetrable particles interacting through positive, purely repulsive, pair-potentials. Starting from some lower bounds to the total potential energy, we draw results on the thermodynamic limit of the given model.
Magnetic properties in an alternating-spin ferromagnetic Ising chain
NASA Astrophysics Data System (ADS)
Eloy, D.; Ramos, F. B.
2011-08-01
Using the transfer matrix technique, we investigated the magnetic properties of a ferromagnetic Ising chain with alternating-spins ( S, S') and single-ion anisotropy. We have calculated some physical quantities of interest such as the z component of the total magnetization per particle ( m) and magnetic susceptibility. In the regime of low temperatures, we observed the existence of magnetization plateaus. We constructed the phase diagrams of the magnetization in terms of the magnetic field and of the single-ion anisotropy for the case {1}/{2}≤(S,S')≤{9}/{2}. We were able to find a general rule for the magnetic transitions. We observed that the saturation value of the magnetization is msat=(S+S')/2.
Correlated Exciton Transport in Rydberg-Dressed-Atom Spin Chains.
Schempp, H; Günter, G; Wüster, S; Weidemüller, M; Whitlock, S
2015-08-28
We investigate the transport of excitations through a chain of atoms with nonlocal dissipation introduced through coupling to additional short-lived states. The system is described by an effective spin-1/2 model where the ratio of the exchange interaction strength to the reservoir coupling strength determines the type of transport, including coherent exciton motion, incoherent hopping, and a regime in which an emergent length scale leads to a preferred hopping distance far beyond nearest neighbors. For multiple impurities, the dissipation gives rise to strong nearest-neighbor correlations and entanglement. These results highlight the importance of nontrivial dissipation, correlations, and many-body effects in recent experiments on the dipole-mediated transport of Rydberg excitations.
Random matrix theory and critical phenomena in quantum spin chains.
Hutchinson, J; Keating, J P; Mezzadri, F
2015-09-01
We compute critical properties of a general class of quantum spin chains which are quadratic in the Fermi operators and can be solved exactly under certain symmetry constraints related to the classical compact groups U(N),O(N), and Sp(2N). In particular we calculate critical exponents s,ν, and z, corresponding to the energy gap, correlation length, and dynamic exponent, respectively. We also compute the ground state correlators 〈σ_{i}^{x}σ_{i+n}^{x}〉_{g},〈σ_{i}^{y}σ_{i+n}^{y}〉_{g}, and 〈∏_{i=1}^{n}σ_{i}^{z}〉_{g}, all of which display quasi-long-range order with a critical exponent dependent upon system parameters. Our approach establishes universality of the exponents for the class of systems in question.
Observation of prethermalization in long-range interacting spin chains
Neyenhuis, Brian; Zhang, Jiehang; Hess, Paul W.; Smith, Jacob; Lee, Aaron C.; Richerme, Phil; Gong, Zhe-Xuan; Gorshkov, Alexey V.; Monroe, Christopher
2017-01-01
Although statistical mechanics describes thermal equilibrium states, these states may or may not emerge dynamically for a subsystem of an isolated quantum many-body system. For instance, quantum systems that are near-integrable usually fail to thermalize in an experimentally realistic time scale, and instead relax to quasi-stationary prethermal states that can be described by statistical mechanics, when approximately conserved quantities are included in a generalized Gibbs ensemble (GGE). We experimentally study the relaxation dynamics of a chain of up to 22 spins evolving under a long-range transverse-field Ising Hamiltonian following a sudden quench. For sufficiently long-range interactions, the system relaxes to a new type of prethermal state that retains a strong memory of the initial conditions. However, the prethermal state in this case cannot be described by a standard GGE; it rather arises from an emergent double-well potential felt by the spin excitations. This result shows that prethermalization occurs in a broader context than previously thought, and reveals new challenges for a generic understanding of the thermalization of quantum systems, particularly in the presence of long-range interactions. PMID:28875166
Observation of prethermalization in long-range interacting spin chains.
Neyenhuis, Brian; Zhang, Jiehang; Hess, Paul W; Smith, Jacob; Lee, Aaron C; Richerme, Phil; Gong, Zhe-Xuan; Gorshkov, Alexey V; Monroe, Christopher
2017-08-01
Although statistical mechanics describes thermal equilibrium states, these states may or may not emerge dynamically for a subsystem of an isolated quantum many-body system. For instance, quantum systems that are near-integrable usually fail to thermalize in an experimentally realistic time scale, and instead relax to quasi-stationary prethermal states that can be described by statistical mechanics, when approximately conserved quantities are included in a generalized Gibbs ensemble (GGE). We experimentally study the relaxation dynamics of a chain of up to 22 spins evolving under a long-range transverse-field Ising Hamiltonian following a sudden quench. For sufficiently long-range interactions, the system relaxes to a new type of prethermal state that retains a strong memory of the initial conditions. However, the prethermal state in this case cannot be described by a standard GGE; it rather arises from an emergent double-well potential felt by the spin excitations. This result shows that prethermalization occurs in a broader context than previously thought, and reveals new challenges for a generic understanding of the thermalization of quantum systems, particularly in the presence of long-range interactions.
Effective computation of quantum discord in a multiqubit spin chain
NASA Astrophysics Data System (ADS)
Chernyavskiy, A.
2016-12-01
Quantum discord is a non-classical correlation beyond quantum entanglement, which is a possible resource for quantum information technologies. The computation of quantum discord is a difficult problem due to the necessity of global optimization. We present the original semi-algebraic method for the effective computation of discord in the multi-qubit spin chain interacting with the impurity spin. We use the random mutations algorithm in a non-standard way: not for the minimization, but for the verification of inequalities. More specifically, we use it to check the constancy condition of the minimum of conditional entropy. After that, the discord can be calculated effectively by the algebraic procedures, and we construct the discord surface for different values of the structural parameter of the model. The considered approach for the verification of inequalities by global optimization algorithms can be used in a wide variety of applications, especially, in the theory of quantum correlations, which contains a lot of definitions based on minimums and maximums.
NASA Astrophysics Data System (ADS)
Köppen, M.; Lang, M.; Helfrich, R.; Steglich, F.; Thalmeier, P.; Schmidt, B.; Wand, B.; Pankert, D.; Benner, H.; Aoki, H.; Ochiai, A.
1999-05-01
We report low-temperature measurements of the specific heat, thermal expansion, and thermal conductivity on the quasi-one-dimensional, effective S = 12 Heisenberg antiferromagnet Yb4As3. Distinct field-induced anomalies were found in the above quantities which are well described by the classical sine-Gordon soliton solution for an easy-plane Heisenberg antiferromagnet. Our findings strongly suggest that Yb4As3 represents the first example of an antiferromagnetic S = 12 spin-chain system where this type of nonlinear excitation could be identified.
Polarization hydrodynamics in a one-dimensional polariton condensate
NASA Astrophysics Data System (ADS)
Larré, P.-É.; Pavloff, N.; Kamchatnov, A. M.
2013-12-01
We study the hydrodynamics of a nonresonantly pumped polariton condensate in a quasi-one-dimensional quantum wire taking into account the spin degree of freedom. We clarify the relevance of the Landau criterion for superfluidity in this dissipative two-component system. Two Cherenkov-like critical velocities are identified corresponding to the opening of different channels of radiation: one of (damped) density fluctuations and another of (weakly damped) polarization fluctuations. We determine the drag force exerted onto an external obstacle and propose experimentally measurable consequences of the specific features of the fluctuations of polarization.
Direct three-dimensional ordering of quasi-one-dimensional quantum dimer system near critical fields
NASA Astrophysics Data System (ADS)
Matsushita, Taku; Hori, Nobuyoshi; Takata, Seiya; Wada, Nobuo; Amaya, Naoki; Hosokoshi, Yuko
2017-01-01
Dimensionalities of X X Z spin orderings or degenerate hard-core bosons in a quasi-one-dimensional (1D) dimer system are examined by the ac susceptibility and specific heat of antiferromagnetic bond-alternating chains in pentafluorophenyl nitronyl nitroxide (F5PNN ). At intermediate fields in the gapless region, the 1D short-range order (SRO) corresponding to the Tomonaga-Luttinger liquid and three-dimensional (3D) long-range order (LRO BEC) at lower temperatures are separately observed, as expected from the small interchain interaction. In contrast, a definite region around the critical field was established where 3D LRO occurs without the development of 1D SRO at higher temperatures.
Entanglement across extended random defects in the XX spin chain
NASA Astrophysics Data System (ADS)
Juhász, Róbert
2017-08-01
We study the half-chain entanglement entropy in the ground state of the spin-1/2 XX chain across an extended random defect, where the strength of disorder decays with the distance from the interface algebraically as Δ_l∼ l-κ . In the whole regime κ≥slant 0 , the average entanglement entropy is found to increase logarithmically with the system size L as S_L≃\\frac{c_eff(κ)}{6}\\ln L+const , where the effective central charge c_eff(κ) depends on κ. In the regime κ<1/2 , where the extended defect is a relevant perturbation, the strong-disorder renormalization group method gives c_eff(κ)=(1-2κ)\\ln2 , while, in the regime κ≥slant 1/2 , where the extended defect is irrelevant in the bulk, numerical results indicate a non-zero effective central charge, which increases with κ. The variation of c_eff(κ) is thus found to be non-monotonic and discontinuous at κ=1/2 .
Exact spin-cluster ground states in a mixed diamond chain
NASA Astrophysics Data System (ADS)
Takano, Ken'Ichi; Suzuki, Hidenori; Hida, Kazuo
2009-09-01
The mixed diamond chain is a frustrated Heisenberg chain composed of successive diamond-shaped units with two kinds of spins of magnitudes S and S/2 ( S : integer). Ratio λ of two exchange parameters controls the strength of frustration. With varying λ , the Haldane state and several spin-cluster states appear as the ground state. A spin-cluster state is a tensor product of exact local eigenstates of cluster spins. We prove that a spin-cluster state is the ground state in a finite interval of λ . For S=1 , we numerically determine the total phase diagram consisting of five phases.
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.
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.
Spin-stripe phase in a frustrated zigzag spin-1/2 chain
Pregelj, M.; Zorko, A.; Zaharko, O.; Nojiri, H.; Berger, H.; Chapon, L. C.; Arčon, D.
2015-01-01
Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole–dipole interactions in the case of ferromagnetic thin films. Here we show that spin-stripe textures may develop also in antiferromagnets, where long-range dipole–dipole magnetic interactions are absent. A comprehensive analysis of magnetic susceptibility, high-field magnetization, specific heat and neutron diffraction measurements unveils β-TeVO4 as a nearly perfect realization of a frustrated (zigzag) ferromagnetic spin-1/2 chain. Notably, a narrow spin-stripe phase develops at elevated magnetic fields due to weak frustrated short-range interchain exchange interactions, possibly assisted by the symmetry-allowed electric polarization. This concept provides an alternative route for the stripe formation in strongly correlated electron systems and may help understanding of other widespread, yet still elusive, stripe-related phenomena. PMID:26068618
Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains
NASA Astrophysics Data System (ADS)
Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.
2016-10-01
We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.
Transient One-dimensional Pipe Flow Analyzer
1986-04-08
TOPAZ-SNLL, the Transient One- dimensional Pipe flow AnalyZer code, is a user-friendly computer program for modeling the heat transfer, fluid mechanics, and thermodynamics of multi-species gas transfer in arbitrary arrangements of pipes, valves, vessels, and flow branches. Although the flow conservation equations are assumed to be one-dimensional and transient, multidimensional features of internal fluid flow and heat transfer may be accounted for using the available quasi-steady flow correlations (e.g., Moody friction factor correlation and various form loss and heat transfer correlations). Users may also model the effects of moving system boundaries such as pistons, diaphragms, and bladders. The features of fully compressible flow are modeled, including the propagation of shocks and rarefaction waves, as well as the establishment of multiple choke points along the flow path.
NASA Astrophysics Data System (ADS)
Solano-Carrillo, E.; Franco, R.; Silva-Valencia, J.
2011-08-01
We studied the nonequilibrium short-time dynamics of a spin-1/2 chain with Dzyaloshinskii-Moriya interactions after a sudden quench by a transverse field. We found that inhomogeneous spin spirals with opposite chiralities propagate from the edges toward the center of the chain. This propagation is accompanied by quantum spin oscillations which decay asymptotically with time. A theoretical description of this phenomenon is given to a good accuracy with the help of numerical calculations with the adaptive time-dependent density matrix renormalization group algorithm.
One-dimensional opal photonic crystals
NASA Astrophysics Data System (ADS)
Kapitonov, A. M.
2008-12-01
One-dimensional opals are 1D self-assembled close packed colloidal crystals consisting of monodisperse colloidal globules. Polystyrene globules with sizes in the 1.9-10 μm range sit on a flat substrate and touch two neighbors in diametrally opposite contact points. These opals are quasi-1D photonic crystals. Optical modes, including whispering gallery modes of individual globules, coupled collective modes, and nanojet-induced modes, are visualized in 1D opals.
Decoupling-free NMR quantum computer on a quantum spin chain
Goto, Atsushi; Shimizu, Tadashi; Hashi, Kenjiro; Kitazawa, Hideaki; Ohki, Shinobu
2003-02-01
We propose a decoupling-free nuclear-spin quantum computer installed on a quantum electron spin chain with a singlet ground state and a finite spin gap. Qubits are I=1/2 nuclear spins implanted periodically along the quantum spin chain. A magnetic field gradient is applied parallel to the chain, which allows individual access to each qubit. A single-qubit operation (rotation gate) is realized with the rf field tuned to the nuclear Larmor frequency at the qubit of interest, while a two-qubit operation (controlled-NOT gate) is achieved using the Suhl-Nakamura interaction through a packet of triplet magnons, which are excited by a microwave tuned to the spin gap energy (SN gate). The interaction can be switched off by turning off the microwave, and a decoupling-free quantum computer is realized. The initialization is achieved with an optical pumping qubit initializer, which has a multilayered structure of the quantum spin chain and a semiconductor. Spin polarizations created by the optical pumping in the semiconducting layers are transferred to the spin chain layers through a cross polarization and a spin diffusion. The scheme allows us to separate the initialization process from the computation, enabling us to optimize the latter independently of the former.
NASA Astrophysics Data System (ADS)
Yannouleas, Constantine; Brandt, Benedikt B.; Landman, Uzi
2016-07-01
Advances with trapped ultracold atoms intensified interest in simulating complex physical phenomena, including quantum magnetism and transitions from itinerant to non-itinerant behavior. Here we show formation of antiferromagnetic ground states of few ultracold fermionic atoms in single and double well (DW) traps, through microscopic Hamiltonian exact diagonalization for two DW arrangements: (i) two linearly oriented one-dimensional, 1D, wells, and (ii) two coupled parallel wells, forming a trap of two-dimensional, 2D, nature. The spectra and spin-resolved conditional probabilities reveal for both cases, under strong repulsion, atomic spatial localization at extemporaneously created sites, forming quantum molecular magnetic structures with non-itinerant character. These findings usher future theoretical and experimental explorations into the highly correlated behavior of ultracold strongly repelling fermionic atoms in higher dimensions, beyond the fermionization physics that is strictly applicable only in the 1D case. The results for four atoms are well described with finite Heisenberg spin-chain and cluster models. The numerical simulations of three fermionic atoms in symmetric DWs reveal the emergent appearance of coupled resonating 2D Heisenberg clusters, whose emulation requires the use of a t-J-like model, akin to that used in investigations of high T c superconductivity. The highly entangled states discovered in the microscopic and model calculations of controllably detuned, asymmetric, DWs suggest three-cold-atom DW quantum computing qubits.
A family of spin-S chain representations of SU(2) level k Wess-Zumino-Witten models
NASA Astrophysics Data System (ADS)
Greiter, Martin; Thomale, Ronny; Rachel, Stephan; Schmitteckert, Peter
2012-02-01
We investigate a family of spin-S chain Hamiltonians recently introduced by one of us [M. Greiter, Mapping of Parent Hamiltonians, Springer Tracts in Modern Phyiscs, Vol 244 (Springer, Berlin, 2011)]. For S=1/2, it corresponds to the Haldane--Shastry model. For general spin S, we numerically show that the low--energy theory of these spin chains is described by the SU(2)k Wess--Zumino--Witten model with coupling k=2S. In particular, we investigate the S=1 model whose ground state is given by a Pfaffian for even number of sites N. We reconcile aspects of the spectrum of the Hamiltonian for arbitrary N with trial states obtained by Schwinger projection of two Haldane--Shastry chains.
Enhancement of antiferromagnetic coupling in the quasi-one-dimensional Ca3Co2O6 ferrimagnet
NASA Astrophysics Data System (ADS)
Martínez, B.; Laukhin, V.; Hernando, M.; Fontcuberta, J.; Parras, M.; González-Calbet, J. M.
2001-07-01
The magnetic coupling between quasi-one-dimensional ferromagnetic chains in Ca3Co2O6 oxide has been studied using magnetic measurements under quasihydrostatic pressure (P) up to 12 kbar. It is found that the low-temperature ferrimagnetic phase, resulting from the antiferromagnetic coupling of ferromagnetic chains, is stabilized under pressure. Both the critical field for the spin-flip transition of the linear chains (HSF) and the temperature T* where the long-range ferrimagnetic ordering sets in rise under pressure with the following rates: dHSF/dP~135-155 Oe/kbar and dT*/dP~0.073 K/kbar, respectively. We show that these variations can be accurately described in terms of the interchain bond-length compression.
Systematic classical continuum limits of integrable spin chains and emerging novel dualities
NASA Astrophysics Data System (ADS)
Avan, Jean; Doikou, Anastasia; Sfetsos, Konstadinos
2010-12-01
We examine certain classical continuum long wave-length limits of prototype integrable quantum spin chains. We define the corresponding construction of classical continuum Lax operators. Our discussion starts with the XXX chain, the anisotropic Heisenberg model and their generalizations and extends to the generic isotropic and anisotropic gl magnets. Certain classical and quantum integrable models emerging from special "dualities" of quantum spin chains, parametrized by c-number matrices, are also presented.
NASA Astrophysics Data System (ADS)
Liu, Xi-Jing; Hu, Bing-Quan; Cho, Sam Young; Zhou, Huan-Qiang; Shi, Qian-Qian
2016-10-01
Recently, the finite-size corrections to the geometrical entanglement per lattice site in the spin-1/2 chain have been numerically shown to scale inversely with system size, and its prefactor b has been suggested to be possibly universal [Q-Q. Shi et al., New J. Phys. 12, 025008 (2010)]. As possible evidence of its universality, the numerical values of the prefactors have been confirmed analytically by using the Affleck-Ludwig boundary entropy with a Neumann boundary condition for a free compactified field [J-M. Stephan et al., Phys. Rev. B 82, 180406(R) (2010)]. However, the Affleck-Ludwig boundary entropy is not unique and does depend on conformally invariant boundary conditions. Here, we show that a unique Affleck-Ludwig boundary entropy corresponding to a finitesize correction to the geometrical entanglement per lattice site exists and show that the ratio of the prefactor b to the corresponding minimum groundstate degeneracy gmin for the Affleck- Ludwig boundary entropy is a constant for any critical region of the spin-1 XXZ system with the single-ion anisotropy, i.e., b/(2 log2 g min ) = -1. Previously studied spin-1/2 systems, including the quantum three-state Potts model, have verified the universal ratio. Hence, the inverse finite-size correction to the geometrical entanglement per lattice site and its prefactor b are universal for one-dimensional critical systems.
NASA Astrophysics Data System (ADS)
Chen, Cheng-Chien; van Veenendaal, Michel; Devereaux, Thomas P.; Wohlfeld, Krzysztof
2015-04-01
Using a combined analytical and numerical approach, we study the collective spin and orbital excitations in a spin-orbital chain under a crystal field. Irrespective of the crystal-field strength, these excitations can be universally described by fractionalized fermions. The fractionalization phenomenon persists and contrasts strikingly with the case of a spin chain, where fractionalized spinons cannot be individually observed but confined to form magnons in a strong magnetic field. In the spin-orbital chain, each of the fractional quasiparticles carries both spin and orbital quantum numbers, and the two variables are always entangled in the collective excitations. Our result further shows that the recently reported separation phenomenon occurs when crystal fields fully polarize the orbital degrees of freedom. In this case, however, the spinon and orbiton dynamics are decoupled solely because of a redefinition of the spin and orbital quantum numbers.
NASA Astrophysics Data System (ADS)
Pike, Nicholas A.; Stroud, David
2017-03-01
We calculate the dispersion relations for spin waves on a periodic chain of spherical or cylindrical Yttrium Iron Garnet (YIG) particles. We use the quasistatic approximation, appropriate when kd ≪ 1, where k is the wave number and d the interparticle spacing. In this regime, because of the magnetic dipole-dipole interaction between the localized magnetic excitations on neighboring particles, dispersive spin waves can propagate along the chain. The waves are analogous to plasmonic waves generated by electric dipole-dipole interactions between plasmons on neighboring metallic particles. The spin waves can be longitudinal (L), transverse (T), or elliptically polarized. We find that a linearly polarized spin wave undergoes a Faraday rotation as it propagates along the chain. The amount of Faraday rotation can be tuned by varying the off-diagonal component of the permeability tensor. We also discuss the possibility of wireless power transmission along the chain using these coupled spin waves.
Random dilution effects in the frustrated spin chain β -CaCr2 -xScxO4
NASA Astrophysics Data System (ADS)
Songvilay, M.; Petit, S.; Hardy, V.; Castellan, J. P.; André, G.; Martin, C.; Damay, F.
2015-02-01
Random dilution effects in the magnetic zigzag ladder (J1-J2 chain) β -CaC r2 -xS cxO4 have been investigated combining magnetic susceptibility, specific heat measurements, and neutron scattering. The pseudogapped magnetic excitations observed above TN in β -CaC r2O4 (x =0 ) persist up to x =0.3 with an increasing characteristic frequency E0 but vanish for x =0.5 for which a quasielastic signal extending up to 8 meV becomes the characteristic feature of the magnetic spectrum. Magnetic ordering is seen up to x =0.3 with decreased ordering temperature TN and correlation length. The results are interpreted in terms of the progressive confinement of one-dimensional excitations within shorter chains as x increases and emphasize the crucial role of J2 in propagating magnetic excitations. For an average chain length l smaller than ˜16 magnetic atoms, the system breaks apart into a set of disconnected units with the dynamical properties of a spin glass.
Singular eigenstates in the even(odd) length Heisenberg spin chain
NASA Astrophysics Data System (ADS)
Ranjan Giri, Pulak; Deguchi, Tetsuo
2015-05-01
We study the implications of the regularization for the singular solutions on the even(odd) length spin-1/2 XXX chains in some specific down-spin sectors. In particular, the analytic expressions of the Bethe eigenstates for three down-spin sector have been obtained along with their numerical forms in some fixed length chains. For an even-length chain if the singular solutions \\{{{λ }α }\\} are invariant under the sign changes of their rapidities \\{{{λ }α }\\}=\\{-{{λ }α }\\}, then the Bethe ansatz equations are reduced to a system of (M-2)/2((M-3)/2) equations in an even (odd) down-spin sector. For an odd N length chain in the three down-spin sector, it has been analytically shown that there exist singular solutions in any finite length of the spin chain of the form N=3(2k+1) with k=1,2,3,\\cdots . It is also shown that there exist no singular solutions in the four down-spin sector for some odd-length spin-1/2 XXX chains.
A one-dimensional tunable magnetic metamaterial.
Butz, S; Jung, P; Filippenko, L V; Koshelets, V P; Ustinov, A V
2013-09-23
We present experimental data on a one-dimensional super-conducting metamaterial that is tunable over a broad frequency band. The basic building block of this magnetic thin-film medium is a single-junction (rf-) superconducting quantum interference device (SQUID). Due to the nonlinear inductance of such an element, its resonance frequency is tunable in situ by applying a dc magnetic field. We demonstrate that this results in tunable effective parameters of our metamaterial consisting of 54 rf-SQUIDs. In order to obtain the effective magnetic permeability μr,eff from the measured data, we employ a technique that uses only the complex transmission coefficient S₂₁.
Electrodeposition of one-dimensional nanostructures.
She, Guangwei; Mu, Lixuan; Shi, Wensheng
2009-01-01
Electrodeposition is a simple and flexible method for the synthesis of one-dimensional (1D) nanostructures and has attracted more and more attention in recent years. 1D nanostructures of metals, semiconductors and polymers have been successfully fabricated by electrodeposition. Templates were often used in the electrochemical process to realize the 1D growth. On the other hand, some materials with intrinsic anisotropic crystal structures can also be prepared by the template-free electrochemical method. In this paper, we review the recent patents progress and offer some prospects of future directions in electrodeposition of 1D nanostructures.
One-dimensional circular diffraction patterns
NASA Astrophysics Data System (ADS)
Daimon, Hiroshi; Ino, Shozo
1989-11-01
Circular diffraction patterns from a bulk crystal have been found in MEED patterns by using a newly developed two-dimensional spherical mirror analyzer. From the analysis of the energy dependence of their radii and from the fact that they are not associated with the tangential Kikuchi lines, the circles were interpreted by the concept of one-dimensional diffraction along the crystallographic axes. The hemi-circular patterns, which have been observed in RHEED patterns near superstructural spots from a surface structure, were also explained by this concept.
One-dimensional hypersonic phononic crystals.
Gomopoulos, N; Maschke, D; Koh, C Y; Thomas, E L; Tremel, W; Butt, H-J; Fytas, G
2010-03-10
We report experimental observation of a normal incidence phononic band gap in one-dimensional periodic (SiO(2)/poly(methyl methacrylate)) multilayer film at gigahertz frequencies using Brillouin spectroscopy. The band gap to midgap ratio of 0.30 occurs for elastic wave propagation along the periodicity direction, whereas for inplane propagation the system displays an effective medium behavior. The phononic properties are well captured by numerical simulations. The porosity in the silica layers presents a structural scaffold for the introduction of secondary active media for potential coupling between phonons and other excitations, such as photons and electrons.
One-dimensional ZnO nanostructures.
Jayadevan, K P; Tseng, T Y
2012-06-01
The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.
The quench action approach in finite integrable spin chains
NASA Astrophysics Data System (ADS)
Alba, Vincenzo; Calabrese, Pasquale
2016-04-01
We consider the problem of constructing the stationary state following a quantum quench, using the exact overlaps for finite size integrable models. We focus on the isotropic Heisenberg spin chain with initial state Néel or Majumdar-Ghosh (dimer), although the proposed approach is valid for an arbitrary integrable model. We consider only eigenstates which do not contain zero-momentum strings because the latter are affected by fictitious singularities that are very difficult to take into account. We show that the fraction of eigenstates that do not contain zero-momentum strings is vanishing in the thermodynamic limit. Consequently, restricting to this part of the Hilbert space leads to vanishing expectation values of local observables. However, it is possible to reconstruct the asymptotic values by properly reweighting the expectations in the considered subspace, at the price of introducing finite-size corrections. We also develop a Monte Carlo sampling of the Hilbert space which allows us to study larger systems. We accurately reconstruct the expectation values of the conserved charges and the root distributions in the stationary state, which turn out to match the exact thermodynamic results. The proposed method can be implemented even in cases in which an analytic thermodynamic solution is not obtainable.
NASA Astrophysics Data System (ADS)
Wang, Dong; Ming, Fei; Huang, Ai-Jun; Sun, Wen-Yang; Ye, Liu
2017-09-01
The uncertainty principle configures a low bound to the measuring precision for a pair of non-commuting observables, and hence is considerably nontrivial to quantum precision measurement in the field of quantum information theory. In this letter, we consider the entropic uncertainty relation (EUR) in the context of quantum memory in a two-qubit isotropic Heisenberg spin chain. Specifically, we explore the dynamics of EUR in a practical scenario, where two associated nodes of a one-dimensional XXX-spin chain, under an inhomogeneous magnetic field, are connected to a thermal entanglement. We show that the temperature and magnetic field effect can lead to the inflation of the measuring uncertainty, stemming from the reduction of systematic quantum correlation. Notably, we reveal that, firstly, the uncertainty is not fully dependent on the observed quantum correlation of the system; secondly, the dynamical behaviors of the measuring uncertainty are relatively distinct with respect to ferromagnetism and antiferromagnetism chains. Meanwhile, we deduce that the measuring uncertainty is dramatically correlated with the mixedness of the system, implying that smaller mixedness tends to reduce the uncertainty. Furthermore, we propose an effective strategy to control the uncertainty of interest by means of quantum weak measurement reversal. Therefore, our work may shed light on the dynamics of the measuring uncertainty in the Heisenberg spin chain, and thus be important to quantum precision measurement in various solid-state systems.
Excitations in a four-leg antiferromagnetic Heisenberg spin tube
Garlea, Vasile O; Zheludev, Andrey I; Regnault, L.-P.; Chung, J.-H.; Qiu, Y.; Boehm, Martin; Habicht, Klaus; Meissner, Michael
2008-01-01
Inelastic neutron scattering is used to investigate magnetic excitations in the quasi-one-dimensional quantum spin-liquid system Cu$_2$Cl$_{4}\\cdot$ D$_8$C$_4$SO$_2$. Contrary to previously conjectured models that relied on bond-alternating nearest neighbor interactions in the spin chains, the dominant interactions are actually next-nearest-neighbor in-chain antiferromagnetic couplings. The appropriate Heisenberg Hamiltonian is equivalent to that of a $S=1/2$ 4-leg spin-tube with almost perfect one dimensionality and no bond alternation. A partial geometric frustration of rung interactions induces a small incommensurability of short-range spin correlations.
Excitations in a Four-Leg Antiferromagnetic Heisenberg Spin Tube,
Garlea, Vasile O; Zheludev, Andrey I; Regnault, L.-P.; Chung, J.-H.; Qiu, Y.; Boehm, Martin; Habicht, Klaus; Meissner, Michael; Fernandez-Baca, Jaime A
2008-01-01
Inelastic neutron scattering is used to investigate magnetic excitations in the quasi-one-dimensional quantum spin-liquid system Cu2Cl4 D8C4SO2. Contrary to previously conjectured models that relied on bond-alternating nearest-neighbor interactions in the spin chains, the dominant interactions are actually next-nearest-neighbor in-chain antiferromagnetic couplings. The appropriate Heisenberg Hamiltonian is equivalent to that of a S 1=2 4-leg spin-tube with almost perfect one dimensionality and no bond alternation. A partial geometric frustration of rung interactions induces a small incommensurability of short-range spin correlations.
Excitations in a four-leg antiferromagnetic Heisenberg spin tube.
Garlea, V O; Zheludev, A; Regnault, L-P; Chung, J-H; Qiu, Y; Boehm, M; Habicht, K; Meissner, M
2008-01-25
Inelastic neutron scattering is used to investigate magnetic excitations in the quasi-one-dimensional quantum spin-liquid system Cu(2)Cl(4).D(8)C(4)SO(2). Contrary to previously conjectured models that relied on bond-alternating nearest-neighbor interactions in the spin chains, the dominant interactions are actually next-nearest-neighbor in-chain antiferromagnetic couplings. The appropriate Heisenberg Hamiltonian is equivalent to that of a S=1/2 4-leg spin-tube with almost perfect one dimensionality and no bond alternation. A partial geometric frustration of rung interactions induces a small incommensurability of short-range spin correlations.
Universality of anomalous one-dimensional heat conductivity
NASA Astrophysics Data System (ADS)
Lepri, Stefano; Livi, Roberto; Politi, Antonio
2003-12-01
In one and two dimensions, transport coefficients may diverge in the thermodynamic limit due to long-time correlation of the corresponding currents. The effective asymptotic behavior is addressed with reference to the problem of heat transport in one-dimensional crystals, modeled by chains of classical nonlinear oscillators. Extensive accurate equilibrium and nonequilibrium numerical simulations confirm that the finite-size thermal conductivity diverges with system size L as κ∝Lα. However, the exponent α deviates systematically from the theoretical prediction α=1/3 proposed in a recent paper [O. Narayan and S. Ramaswamy, Phys. Rev. Lett. 89, 200601 (2002)].
Nocera, Alberto; Patel, Niravkumar D.; Fernandez-Baca, Jaime A.; ...
2016-11-28
In this paper, we study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small asmore » U/t ~ 2–3, although ratios of peak intensities at different momenta continue evolving with increasing U/t converging only slowly to the Heisenberg limit. Finally, we discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U/t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.« less
NASA Astrophysics Data System (ADS)
Nocera, A.; Patel, N. D.; Fernandez-Baca, J.; Dagotto, E.; Alvarez, G.
2016-11-01
We study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small as U /t ˜2 -3 , although ratios of peak intensities at different momenta continue evolving with increasing U /t converging only slowly to the Heisenberg limit. We discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U /t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.
Nocera, Alberto; Patel, Niravkumar D.; Fernandez-Baca, Jaime A.; Dagotto, Elbio R.; Alvarez, Gonzalo
2016-11-28
In this paper, we study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small as U/t ~ 2–3, although ratios of peak intensities at different momenta continue evolving with increasing U/t converging only slowly to the Heisenberg limit. Finally, we discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U/t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.
Vector-spin-chirality order in a dimerized frustrated spin-1/2 chain
NASA Astrophysics Data System (ADS)
Ueda, Hiroshi; Onoda, Shigeki
2014-01-01
A frustrated spin-1/2 XXZ chain model comprising a ferromagnetic nearest-neighbor coupling with the bond alternation, J1(1±δ)<0, and an antiferromagnetic second-neighbor exchange coupling J2>0 is studied at zero and weak magnetic fields by means of density-matrix renormalization-group calculations of order parameters, correlation functions, and the entanglement entropy, as well as an Abelian bosonization analysis. At zero magnetic field, the bond alternation δ >0 suppresses the gapless phase characterized by a vector-chiral (VC) long-range order (LRO) and a quasi-LRO of an incommensurate spin spiral, whereas this phase occupies a large region in the space of J1/J2 and the easy-plane exchange anisotropy for δ =0 [S. Furukawa et al., Phys. Rev. Lett. 105, 257205 (2010), 10.1103/PhysRevLett.105.257205]. Then, four gapped phases are found to appear as the exchange anisotropy varies from the SU(2)-symmetric case to the U(1)-symmetric case: the Haldane dimer (D+) phase with the same sign of the x ,y- and z-component dimer order parameters, two VC dimer (VCD+/VCD-) phases with the sign of the z-component dimer order parameter being unaltered/reversed, and the even-parity dimer (D-) phase. At small magnetic fields, a field-induced ring-exchange interaction, which is proportional to a staggered scalar chirality and a magnetic flux penetrating the associated triangle, drives a transition from the D- phase into a VC-Neel-dimer (VCND) phase, but not from the D+ phase. This VCND phase is stable up to the large magnetic field at which the Zeeman term closes the spin gap. A possible relevance to Rb2Cu2Mo3O12 is discussed.
The magnetism and spin-dependent electronic transport properties of boron nitride atomic chains
NASA Astrophysics Data System (ADS)
An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Jiao, Zhaoyong; Wang, Kun
2016-07-01
Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 μB for BnNn-1, 2 μB for BnNn, and 3 μB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied.
The one-dimensional hydrogen atom revisited
NASA Astrophysics Data System (ADS)
Palma, G.; Raff, U.
2006-09-01
The one-dimensional Schrodinger hydrogen atom is an interesting mathematical and physical problem for the study of bound states, eigenfunctions, and quantum-degeneracy issues. This one-dimensional physical system has given rise to some intriguing controversy for more than four decades. Presently, still no definite consensus seems to have been reached. We reanalyzed this apparently controversial problem, approaching it from a Fourier-transform representation method combined with some fundamental (basic) ideas found in self-adjoint extensions of symmetric operators. In disagreement with some previous claims, we found that the complete Balmer energy spectrum is obtained together with an odd-parity set of eigenfunctions. Closed-form solutions in both coordinate and momentum spaces were obtained. No twofold degeneracy was observed as predicted by the degeneracy theorem in one dimension, though it does not necessarily have to hold for potentials with singularities. No ground state with infinite energy exists since the corresponding eigenfunction does not satisfy the Schrodinger equation at the origin.
Specificities of one-dimensional dissipative magnetohydrodynamics
Popov, P. V.
2016-11-15
One-dimensional dynamics of a plane slab of cold (β ≪ 1) isothermal plasma accelerated by a magnetic field is studied in terms of the MHD equations with a finite constant conductivity. The passage to the limit β → 0 is analyzed in detail. It is shown that, at β = 0, the character of the solution depends substantially on the boundary condition for the electric field at the inner plasma boundary. The relationship between the boundary condition for the pressure at β > 0 and the conditions for the electric field at β = 0 is found. The stability of the solution against one-dimensional longitudinal perturbations is analyzed. It is shown that, in the limit β → 0, the stationary solution is unstable if the time during which the acoustic wave propagates across the slab is longer than the time of magnetic field diffusion. The growth rate and threshold of instability are determined, and results of numerical simulation of its nonlinear stage are presented.
A quaternionic map for the steady states of the Heisenberg spin-chain
NASA Astrophysics Data System (ADS)
Mehta, Mitaxi P.; Dutta, Souvik; Tiwari, Shubhanshu
2014-01-01
We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.
Mapping between the Heisenberg XX Spin Chain and Low-Energy QCD
NASA Astrophysics Data System (ADS)
Pérez-García, David; Tierz, Miguel
2014-04-01
By using random matrix models, we uncover a connection between the low-energy sector of four-dimensional QCD at finite volume and the Heisenberg XX model in a 1D spin chain. This connection allows us to relate crucial properties of QCD with physically meaningful properties of the spin chain, establishing a dictionary between both worlds. For the spin chain, we predict a third-order phase transition and a Tracy-Widom law in the transition region. We also comment on possible numerical implications of the connection as well as on possible experimental implementations.
On the semi-classical limit of scalar products of the XXZ spin chain
NASA Astrophysics Data System (ADS)
Jiang, Yunfeng; Brunekreef, Joren
2017-03-01
We study the scalar products between Bethe states in the XXZ spin chain with anisotropy |Δ| > 1 in the semi-classical limit where the length of the spin chain and the number of magnons tend to infinity with their ratio kept finite and fixed. Our method is a natural yet non-trivial generalization of similar methods developed for the XXX spin chain. The final result can be written in a compact form as a contour integral in terms of Faddeev's quantum dilogarithm function, which in the isotropic limit reduces to the classical dilogarithm function.
Single-ion and single-chain magnetism in triangular spin-chain oxides
NASA Astrophysics Data System (ADS)
Seikh, Md. Motin; Caignaert, Vincent; Perez, Olivier; Raveau, Bernard; Hardy, Vincent
2017-05-01
S r4 -xC axM n2Co O9 oxides (x =0 and x =2 ) are found to exhibit magnetic responses typical of single-chain magnets (SCMs) and single-ion magnets (SIMs), two features generally investigated in coordination polymers or complexes. The compound x =0 appears to be a genuine SCM, in that blocking effects associated with slow spin dynamics yield remanence and coercivity in the absence of long-range ordering (LRO). In addition, SIM signatures of nearly identical nature are detected in both compounds, coexisting with SCM in x =0 and with LRO in x =2 . It is also observed that a SCM response can be recovered in x =2 after application of magnetic field. These results suggest that purely inorganic systems could play a valuable role in the topical issue of the interplay among SIM, SCM, and LRO phenomena in low-dimensional magnetism.
Boundary-induced spin-density waves in linear Heisenberg antiferromagnetic spin chains with S ≥1
NASA Astrophysics Data System (ADS)
Dey, Dayasindhu; Kumar, Manoranjan; Soos, Zoltán G.
2016-10-01
Linear Heisenberg antiferromagnets (HAFs) are chains of spin-S sites with isotropic exchange J between neighbors. Open and periodic boundary conditions return the same ground-state energy per site in the thermodynamic limit, but not the same spin SG when S ≥1 . The ground state of open chains of N spins has SG=0 or S , respectively, for even or odd N . Density-matrix renormalization-group calculations with different algorithms for even and odd N are presented up to N =500 for the energy and spin densities ρ (r ,N ) of edge states in HAFs with S =1 , 3/2, and 2. The edge states are boundary-induced spin density waves (BI-SDWs) with ρ (r ,N ) ∝(-1) r -1 for r =1 ,2 ,...,N . The SDWs are in phase when N is odd, are out of phase when N is even, and have finite excitation energy Γ (N ) that decreases exponentially with N for integer S and faster than 1 /N for half integer S . The spin densities and excitation energy are quantitatively modeled for integer S chains longer than 5 ξ spins by two parameters, the correlation length ξ and the SDW amplitude, with ξ =6.048 for S =1 and 49.0 for S =2 . The BI-SDWs of S =3 /2 chains are not localized and are qualitatively different for even and odd N . Exchange between the ends for odd N is mediated by a delocalized effective spin in the middle that increases |Γ (N )| and weakens the size dependence. The nonlinear sigma model (NL σ M ) has been applied to the HAFs, primarily to S =1 with even N , to discuss spin densities and exchange between localized states at the ends as Γ (N ) ∝(-1) Nexp(-N /ξ ) . S =1 chains with odd N are fully consistent with the NL σ M ; S =2 chains have two gaps Γ (N ) with the same ξ as predicted whose ratio is 3.45 rather than 3; the NL σ M is more approximate for S =3 /2 chains with even N and is modified for exchange between ends for odd N .
A light-induced spin crossover actuated single-chain magnet
NASA Astrophysics Data System (ADS)
Liu, Tao; Zheng, Hui; Kang, Soonchul; Shiota, Yoshihito; Hayami, Shinya; Mito, Masaki; Sato, Osamu; Yoshizawa, Kazunari; Kanegawa, Shinji; Duan, Chunying
2013-11-01
Both spin-crossover complexes and molecular nanomagnets display bistable magnetic states, potentially behaving as elementary binary units for information storage. It is a challenge to introduce spin-crossover units into molecular nanomagnets to switch the bistable state of the nanomagnets through external stimuli-tuned spin crossover. Here we report an iron(II) spin-crossover unit and paramagnetic iron(III) ions that are incorporated into a well-isolated double-zigzag chain. The chain exhibits thermally induced reversible spin-crossover and light-induced excited spin-state trapping at the iron(II) sites. Single-chain magnet behaviour is actuated accompanying the synergy between light-induced excited spin-state trapping at the iron(II) sites and ferromagnetic interactions between the photoinduced high-spin iron(II) and low-spin iron(III) ions in the chain. The result provides a strategy to switch the bistable state of molecular nanomagnets using external stimuli such as light and heat, with the potential to erase and write information at a molecular level.
Elementary excitations for the one-dimensional Hubbard model at finite temperatures
NASA Astrophysics Data System (ADS)
Tomiyama, A.; Suga, S.; Okiji, A.
1997-07-01
The elementary excitations for the one-dimensional Hubbard model at finite temperatures are studied with the use of the Bethe ansatz solution. The formulation is based on the method of Yang and Yang, which was developed for the one-dimensional boson systems with the 0953-8984/9/27/014/img1-function type interaction. The dispersion relations and the excitation spectrums are obtained numerically for the charge and the spin degrees of freedom.
Magnetism and spin transport of carbon chain between armchair graphene nanoribbon electrodes
NASA Astrophysics Data System (ADS)
Farghadan, R.; Yoosefi, M.
2016-09-01
The magnetic and spin transport properties of a carbon chain between two armchair graphene nanoribbon (AGNR) electrodes were studied using tight-binding Hamiltonian, mean-field Hubbard model and Landauer-Butikker formalism. The results showed that only odd-numbered carbon chains show intrinsic magnetic moments in chain-graphene junctions. It was also found that the electronic, magnetic and spin transport properties of carbon chain-graphene junctions strongly depend on the position and the length of the carbon chains between AGNR electrodes. Interestingly, we found a fully spin-polarized transmission near the Fermi energy in all odd-numbered carbon chain-graphene junctions, regardless of their lengths and without any magnetic field and magnetic electrodes.
NASA Astrophysics Data System (ADS)
Juhász, Róbert
2014-03-01
We study the distribution of dynamical quantities in various one-dimensional disordered models, the critical behavior of which is described by an infinite randomness fixed point. In the disordered contact process, the survival probability P (t) is found to show multiscaling in the critical point, meaning that P(t )=t-δ, where the (environment and time-dependent) exponent δ has a universal limit distribution when t →∞. The limit distribution is determined by the strong disorder renormalization group method analytically in the end point of a semi-infinite lattice, where it is found to be exponential, while, in the infinite system, conjectures on its limiting behaviors for small and large δ, which are based on numerical results, are formulated. By the same method, the survival probability in the problem of random walks in random environments is also shown to exhibit multiscaling with an exponential limit distribution. In addition to this, the (imaginary-time) spin-spin autocorrelation function of the random transverse-field Ising chain is found to have a form similar to that of survival probability of the contact process at the level of the renormalization approach. Consequently, a relationship between the corresponding limit distributions in the two problems can be established. Finally, the distribution of the spontaneous magnetization in this model is also discussed.
Multiple magnetic transitions in the spin-1/2 chain antiferromagnet SrCuTe2O6
NASA Astrophysics Data System (ADS)
Ahmed, N.; Tsirlin, A. A.; Nath, R.
2015-06-01
By using thermodynamic measurements and density-functional band-structure calculations, we explore the magnetic behavior of SrCuTe2O6 . Despite being a structural sibling of a three-dimensional frustrated system PbCuTe2O6 , this spin-1/2 quantum magnet shows remarkably different low-temperature behavior. Above 7 K, magnetic susceptibility of SrCuTe2O6 follows the spin-chain model with the antiferromagnetic intrachain coupling of J ≃49.3 K. We ascribe this quasi-one-dimensional behavior to the leading third-neighbor coupling that involves a weakly bent Cu -O ⋯O -Cu superexchange pathway with a short O ⋯O contact of 2.79 Å. Below 5 K, SrCuTe2O6 undergoes two consecutive magnetic transitions that may be triggered by the frustrated nature of interchain couplings. The field dependence of the magnetic transitions (phase diagram) is reported.
The open XXZ spin chain model and the topological basis realization
NASA Astrophysics Data System (ADS)
Wang, Qingyong; Du, Yangyang; Wu, Chunfeng; Wang, Gangcheng; Sun, Chunfang; Xue, Kang
2016-07-01
In this paper, it is shown that the Hamiltonian of the open spin-1 XXZ chain model can be constructed from the generators of the Birman-Murakami-Wenzl (B-M-W) algebra. Without the topological parameter d (describing the unknotted loop ◯ in topology) reducing to a fixed value, the topological basis states can be connected with the open XXZ spin chain. Then some particular properties of the topological basis states in this system have been investigated. We find that the topological basis states are the three eigenstates of a four-spin-1 XXZ chain model without boundary term. Specifically, all the spin single states of the system fall on the topological basis subspace. And the number of the spin single states of the system is equal to that of the topological basis states.
Superfluid helium-4 in one dimensional channel
NASA Astrophysics Data System (ADS)
Kim, Duk Y.; Banavar, Samhita; Chan, Moses H. W.; Hayes, John; Sazio, Pier
2013-03-01
Superfluidity, as superconductivity, cannot exist in a strict one-dimensional system. However, the experiments employing porous media showed that superfluid helium can flow through the pores of nanometer size. Here we report a study of the flow of liquid helium through a single hollow glass fiber of 4 cm in length with an open id of 150 nm between 1.6 and 2.3 K. We found the superfluid transition temperature was suppressed in the hollow cylinder and that there is no flow above the transition. Critical velocity at temperature below the transition temperature was determined. Our results bear some similarity to that found by Savard et. al. studying the flow of helium through a nanohole in a silicon nitrite membrane. Experimental study at Penn State is supported by NSF Grants No. DMR 1103159.
Three one-dimensional structural heating programs
NASA Technical Reports Server (NTRS)
Wing, L. D.
1978-01-01
Two computer programs for calculating profiles in a ten-element structure consisting of up to ten materials are presented, along with a third program for calculating the mean temperature for a payload container placed in an orbiting vehicle cargo bay. The three programs are related by the sharing of a common analytical technique; the energy balance is based upon one-dimensional heat transfer. The first program, NQLDW112, assumes a non-ablating surface. NQLDW117 is very similar but allows the outermost element to ablate. NQLDW040 calculates an average temperature profile through an idealized model of the real payload cannister and contents in the cargo bay of an orbiting vehicle.
One-dimensional frequency-based spectroscopy.
Cygan, Agata; Wcisło, Piotr; Wójtewicz, Szymon; Masłowski, Piotr; Hodges, Joseph T; Ciuryło, Roman; Lisak, Daniel
2015-06-01
Recent developments in optical metrology have tremendously improved the precision and accuracy of the horizontal (frequency) axis in measured spectra. However, the vertical (typically absorbance) axis is usually based on intensity measurements that are subject to instrumental errors which limit the spectrum accuracy. Here we report a one-dimensional spectroscopy that uses only the measured frequencies of high-finesse cavity modes to provide complete information about the dispersive properties of the spectrum. Because this technique depends solely on the measurement of frequencies or their differences, it is insensitive to systematic errors in the detection of light intensity and has the potential to become the most accurate of all absorptive and dispersive spectroscopic methods. The experimental results are compared to measurements by two other high-precision cavity-enhanced spectroscopy methods. We expect that the proposed technique will have significant impact in fields such as fundamental physics, gas metrology and environmental remote sensing.
Macroscopic Quantum Tunneling in One Dimensional Superconductor
NASA Astrophysics Data System (ADS)
Chang, Yongmin
Macroscopic quantum tunneling (MQT) in a one dimensional superconductor is discussed based on the microscopic model near the critical temperature. By means of a functional integral approach, a formula for the total decay rate, which is the sum of the thermal activation and quantum mechanical tunneling rate, is derived. The Bounce solution in the imaginary time formalism gives rise to the exponent in the tunneling rate. From the study of fluctuations from the bounce path, the pre-exponential factor has been evaluated. The theory for the tunneling rate is consistent with experimental results for temperatures at which the thermal activation theory fails. As the temperature approaches to the critical temperature, thermal activation over a free energy barrier which separates metastable states is dominant and the theory shows good agreement with experiment over the whole temperature region.
One-Dimensional Photonic Crystal Superprisms
NASA Technical Reports Server (NTRS)
Ting, David
2005-01-01
Theoretical calculations indicate that it should be possible for one-dimensional (1D) photonic crystals (see figure) to exhibit giant dispersions known as the superprism effect. Previously, three-dimensional (3D) photonic crystal superprisms have demonstrated strong wavelength dispersion - about 500 times that of conventional prisms and diffraction gratings. Unlike diffraction gratings, superprisms do not exhibit zero-order transmission or higher-order diffraction, thereby eliminating cross-talk problems. However, the fabrication of these 3D photonic crystals requires complex electron-beam substrate patterning and multilayer thin-film sputtering processes. The proposed 1D superprism is much simpler in structural complexity and, therefore, easier to design and fabricate. Like their 3D counterparts, the 1D superprisms can exhibit giant dispersions over small spectral bands that can be tailored by judicious structure design and tuned by varying incident beam direction. Potential applications include miniature gas-sensing devices.
Collapsing of chaos in one dimensional maps
NASA Astrophysics Data System (ADS)
Yuan, Guocheng; Yorke, James A.
2000-02-01
In their numerical investigation of the family of one dimensional maps f l(x)=1-2∣x∣ l, where l>2 , Diamond et al. [P. Diamond et al., Physica D 86 (1999) 559-571] have observed the surprising numerical phenomenon that a large fraction of initial conditions chosen at random eventually wind up at -1, a repelling fixed point. This is a numerical artifact because the continuous maps are chaotic and almost every (true) trajectory can be shown to be dense in [-1,1]. The goal of this paper is to extend and resolve this obvious contradiction. We model the numerical simulation with a randomly selected map. While they used 27 bit precision in computing f l, we prove for our model that this numerical artifact persists for an arbitrary high numerical prevision. The fraction of initial points eventually winding up at -1 remains bounded away from 0 for every numerical precision.
One-dimensional Vlasov-Maxwell equilibria
NASA Astrophysics Data System (ADS)
Greene, John M.
1993-06-01
The purpose of this paper is to show that the Vlasov equilibrium of a plasma of charged particles in an electromagnetic field is closely related to a fluid equilibrium, where only a few moments of the velocity distribution of the plasma are considered. In this fluid equilibrium the electric field should be calculated from Ohm's law, rather than the Poisson equation. In practice, only one-dimensional equilibria are treated, because the symmetry makes this case tractable. The emphasis here is on gaining a better understanding of the subject, but an alternate way of doing the calculations is suggested. It is shown that particle distributions can be found that are consistent with any reasonable electromagnetic field profile.
Fogler, Michael M
2002-05-06
A long-standing problem of the low-energy dynamics of a disordered XY spin chain is reexamined. The case of a rigid chain is studied, where the quantum effects can be treated quasiclassically. It is shown that, as the frequency decreases, the relevant excitations change from localized spin waves to two-level systems to soliton-antisoliton pairs. The linear-response correlation functions are calculated. The results apply to other periodic glassy systems such as pinned density waves, planar vortex lattices, stripes, and disordered Luttinger liquids.
Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei
2014-01-01
We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376
Spinon excitations in the spin-1 XXZ chain and hidden supersymmetry
NASA Astrophysics Data System (ADS)
Matsui, Chihiro
2016-12-01
We study spinon excitations of the integrable spin-1 (Fateev-Zamolodchikov; FZ) chain and their relation to the hidden supersymmetry. Using the notion of the supercharges earlier introduced to the spin chains, which change the system length by one, we found that they nontrivially act on one of two kinds of the degrees of freedom for the FZ chain. Their actions were obtained to be the same as those of the supercharges defined on the supersymmetric sine-Gordon model, the low-energy effective field theory of the FZ chain. Moreover, we construct the eigenstates which are invariant under the supersymmetric Hamiltonian given as the anti-commutator of the supercharges.
NASA Astrophysics Data System (ADS)
Deguchi, Tetsuo; Matsui, Chihiro
2010-06-01
For the integrable higher-spin XXX and XXZ spin chains we present multiple-integral representations for the correlation function of an arbitrary product of Hermitian elementary matrices in the massless ground state. We give a formula expressing it by a single term of multiple integrals. In particular, we explicitly derive the emptiness formation probability (EFP). We assume 2s-strings for the ground-state solution of the Bethe-ansatz equations for the spin-s XXZ chain, and solve the integral equations for the spin-s Gaudin matrix. In terms of the XXZ coupling Δ we define ζ by Δ=cos ζ, and put it in a region 0⩽ζ<π/2s of the gapless regime: -1<Δ⩽1 (0⩽ζ<π), where Δ=1 (ζ=0) corresponds to the antiferromagnetic point. We calculate the zero-temperature correlation functions by the algebraic Bethe-ansatz, introducing the Hermitian elementary matrices in the massless regime, and taking advantage of the fusion construction of the R-matrix of the higher-spin representations of the affine quantum group.
Sergeicheva, E. G.; Sosin, S. S.; Prozorova, L. A.; ...
2017-01-18
We report on an electron spin resonance (ESR) study of a nearly one-dimensional (1D) spin-1/2 chain antiferromagnet, Sr2CuO3, with extremely weak magnetic ordering. The ESR spectra at T > TN, in the disordered Luttinger-spin-liquid phase, reveal nearly ideal Heisenberg-chain behavior with only a very small, field-independent linewidth, ~1/T. In the ordered state, below TN, we identify field-dependent antiferromagnetic resonance modes, which are well described by pseudo-Goldstone magnons in the model of a collinear biaxial antiferromagnet. Additionally, we observe a major resonant mode with unusual and strongly anisotropic properties, which is not anticipated by the conventional theory of Goldstone spin waves.more » Lastly, we propose that this unexpected magnetic excitation can be attributed to a field-independent magnon mode renormalized due to its interaction with the high-energy amplitude (Higgs) mode in the regime of weak spontaneous symmetry breaking.« less
One-dimensional Co(II)/Ni(II) complexes of 2-hydroxyisophthalate: Structures and magnetic properties
Wang, Kai; Zou, Hua-Hong; Chen, Zi-Lu; Zhang, Zhong; Sun, Wei-Yin; Liang, Fu-Pei
2015-03-15
The solvothermal reactions of 2-hydroxyisophthalic acid (H{sub 3}ipO) with M(NO{sub 3}){sub 2}∙6H{sub 2}O (M=Co, Ni) afforded two complexes [Co{sub 2}(HipO){sub 2}(Py){sub 2}(H{sub 2}O){sub 2}] (1) and [Ni(HipO)(Py)H{sub 2}O] (2) (Py=pyridine). They exhibit similar zig-zag chain structures with the adjacent two metal centers connected by a anti-syn bridging carboxylate group from the HipO{sup 2−} ligand. The magnetic measurements reveal the dominant antiferromagnetic interactions and spin-canting in 1 while ferromagnetic interactions in 2. Both of them exhibit magnetocaloric effect (MCE) with the resulting entropy changes (−ΔS{sub m}) of 12.51 J kg{sup −1} K{sup −1} when ΔH=50 kOe at 3 K for 1 and 11.01 J kg{sup −1} K{sup −1} when ΔH=50 kOe at 3 K for 2, representing the rare examples of one-dimensional complexes with MCE. - Graphical abstract: Synopsis: Two Co(II)/Ni(II) complexes with zig-zag chain structures have been reported. 1-Co shows cant-antiferromagnetism while 2-Ni shows ferromagnetism. Magnetocaloric effect is also found in both of them. - Highlights: • Two one-dimensional Co(II)/Ni(II) complexes were solvothermally synthesized. • The Co-complex exhibits canted antiferromagnetism. • The Ni-complex exhibits ferromagnetism. • Both of the complexes display magnetocaloric effect.
Topological basis realization for BMW algebra and Heisenberg XXZ spin chain model
NASA Astrophysics Data System (ADS)
Liu, Bo; Xue, Kang; Wang, Gangcheng; Liu, Ying; Sun, Chunfang
2015-04-01
In this paper, we study three-dimensional (3D) reduced Birman-Murakami-Wenzl (BMW) algebra based on topological basis theory. Several examples of BMW algebra representations are reviewed. We also discuss a special solution of BMW algebra, which can be used to construct Heisenberg XXZ model. The theory of topological basis provides a useful method to solve quantum spin chain models. It is also shown that the ground state of XXZ spin chain is superposition state of topological basis.
Majorana fermion exchange in quasi-one-dimensional networks
NASA Astrophysics Data System (ADS)
Clarke, David J.; Sau, Jay D.; Tewari, Sumanta
2011-07-01
Heterostructures of spin-orbit coupled materials with s-wave superconductors are thought to be capable of supporting zero-energy Majorana bound states. Such excitations are known to obey non-Abelian statistics in two dimensions, and are thus relevant to topological quantum computation (TQC). In a one-dimensional system, Majorana states are localized to phase boundaries. In order to bypass the constraints of one dimension, a wire network may be created, allowing the exchange of Majoranas by way of junctions in the network. Alicea have proposed such a network as a platform for TQC, showing that the Majorana bound states obey non-Abelian exchange statistics even in quasi-one-dimensional systems. Here we show that the particular realization of non-Abelian statistics produced in a Majorana wire network is highly dependent on the local properties of individual wire junctions. For a simply connected network, the possible realizations can be characterized by the chirality of individual junctions. There is in general no requirement for junction chiralities to remain consistent across a wire network. We show how the chiralities of different junctions may be compared experimentally and discuss the implications for TQC in Majorana wire networks.
NASA Astrophysics Data System (ADS)
Knaflič, Tilen; Klanjšek, Martin; Sans, Annette; Adler, Peter; Jansen, Martin; Felser, Claudia; Arčon, Denis
2015-05-01
Recently, it was proposed that the orbital ordering of πx,y * molecular orbitals in the superoxide CsO2 compound leads to the formation of spin-1/2 chains below the structural phase transition occurring at Ts 1=61 K on cooling. Here we report a detailed X -band electron paramagnetic resonance (EPR) study of this phase in CsO2 powder. The EPR signal appears as a broad line below Ts 1, which is replaced by the antiferromagnetic resonance below the Néel temperature TN=8.3 K . The temperature dependence of the EPR linewidth between Ts 1 and TN agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of S =1 /2 spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR line shape, linewidth, and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent K =0.48 . Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO2, which is therefore a unique p -orbital system where such a state could be studied.
A direct proof of dimerization in a family of SU( n)-invariant quantum spin chains
NASA Astrophysics Data System (ADS)
Nachtergaele, Bruno; Ueltschi, Daniel
2017-09-01
We study the family of spin- S quantum spin chains with a nearest neighbor interaction given by the negative of the singlet projection operator. Using a random loop representation of the partition function in the limit of zero temperature and standard techniques of classical statistical mechanics, we prove dimerization for all sufficiently large values of S.
Topological phase in one-dimensional Rashba wire
NASA Astrophysics Data System (ADS)
Sa-Ke, Wang; Jun, Wang; Jun-Feng, Liu
2016-07-01
We study the possible topological phase in a one-dimensional (1D) quantum wire with an oscillating Rashba spin-orbital coupling in real space. It is shown that there are a pair of particle-hole symmetric gaps forming in the bulk energy band and fractional boundary states residing in the gap when the system has an inversion symmetry. These states are topologically nontrivial and can be characterized by a quantized Berry phase ±π or nonzero Chern number through dimensional extension. When the Rashba spin-orbital coupling varies slowly with time, the system can pump out 2 charges in a pumping cycle because of the spin flip effect. This quantized pumping is protected by topology and is robust against moderate disorders as long as the disorder strength does not exceed the opened energy gap. Project supported by the National Natural Science Foundation of China (Grant Nos. 115074045 and 11204187) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20131284).
Charge and energy fractionalization mechanism in one-dimensional channels
NASA Astrophysics Data System (ADS)
Acciai, Matteo; Calzona, Alessio; Dolcetto, Giacomo; Schmidt, Thomas L.; Sassetti, Maura
2017-08-01
We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to charge and energy fractionalization. We elucidate this concept by calculating the nonequilibrium electron distribution function in the momentum and energy domains after the injection of an energy-resolved electron. Our results shed light on how fractionalization occurs via the creation of particle-hole pairs by the injected electron. In particular, we focus on systems with a pair of counterpropagating channels, and we fully analyze the properties of each chiral fractional excitation which is created by the injection. We suggest possible routes to access their energy and momentum distribution functions in topological quantum Hall or quantum spin-Hall edge states.
NASA Astrophysics Data System (ADS)
Vidal, A. J.; Astrakharchik, G. E.; Vranješ Markić, L.; Boronat, J.
2016-05-01
The ground-state properties of one-dimensional electron-spin-polarized hydrogen 1H, deuterium 2H, and tritium 3H are obtained by means of quantum Monte Carlo methods. The equations of state of the three isotopes are calculated for a wide range of linear densities. The pair correlation function and the static structure factor are obtained and interpreted within the framework of the Luttinger liquid theory. We report the density dependence of the Luttinger parameter and use it to identify different physical regimes: Bogoliubov Bose gas, super-Tonks-Girardeau gas, and quasi-crystal regimes for bosons; repulsive, attractive Fermi gas, and quasi-crystal regimes for fermions. We find that the tritium isotope is the one with the richest behavior. Our results show unambiguously the relevant role of the isotope mass in the properties of this quantum system.
Atom-Molecule Coherence in a One-Dimensional System
NASA Astrophysics Data System (ADS)
Citro, R.; Orignac, E.
2005-09-01
We study a model of one-dimensional fermionic atoms with a narrow Feshbach resonance that allows them to bind in pairs to form bosonic molecules. We show that at low energy, a coherence develops between the molecule and fermion Luttinger liquids. At the same time, a gap opens in the spin excitation spectrum. The coherence implies that the order parameters for the molecular Bose-Einstein condensation and the atomic BCS pairing become identical. Moreover, both bosonic and fermionic charge density wave correlations decay exponentially, in contrast with a usual Luttinger liquid. We exhibit a Luther-Emery point where the systems can be described in terms of noninteracting pseudofermions. At this point we discuss the threshold behavior of density-density response functions.
Numerical calculations on the relative entanglement entropy in critical spin chains
NASA Astrophysics Data System (ADS)
Nakagawa, Yuya O.; Ugajin, Tomonori
2017-09-01
We study the relative entanglement entropy (EE) among various primary excited states in two critical spin chains: the S=1/2 XXZ chain and the transverse field Ising chain at criticality. For the S=1/2 XXZ chain, which corresponds to c=1 free boson conformal field theory (CFT), we numerically calculate the relative EE by exact diagonalization and find a perfect agreement with the predictions by the CFT. For the transverse field Ising chain at criticality, which corresponds to the c=1/2 Ising CFT, we analytically relate its relative EE to that of the S=1/2 XXZ chain and confirm the relation numerically. We also calculate the ‘sandwiched’ Rényi relative EE and again the numerical results agree well with the analytical predictions. Our results are the first direct confirmation of the CFT predictions on the relative EE of the primary excited states in critical spin chains.
NASA Astrophysics Data System (ADS)
Eliëns, I. S.; Ramos, F. B.; Xavier, J. C.; Pereira, R. G.
2016-05-01
We study the influence of reflective boundaries on time-dependent responses of one-dimensional quantum fluids at zero temperature beyond the low-energy approximation. Our analysis is based on an extension of effective mobile impurity models for nonlinear Luttinger liquids to the case of open boundary conditions. For integrable models, we show that boundary autocorrelations oscillate as a function of time with the same frequency as the corresponding bulk autocorrelations. This frequency can be identified as the band edge of elementary excitations. The amplitude of the oscillations decays as a power law with distinct exponents at the boundary and in the bulk, but boundary and bulk exponents are determined by the same coupling constant in the mobile impurity model. For nonintegrable models, we argue that the power-law decay of the oscillations is generic for autocorrelations in the bulk, but turns into an exponential decay at the boundary. Moreover, there is in general a nonuniversal shift of the boundary frequency in comparison with the band edge of bulk excitations. The predictions of our effective field theory are compared with numerical results obtained by time-dependent density matrix renormalization group (tDMRG) for both integrable and nonintegrable critical spin-S chains with S =1 /2 , 1, and 3 /2 .