Looking for a quantum spin liquid in the BaNi2(V1−xPx)2O8 spin 1 honeycomb system

The general magnetic characterisation of a series of materials in the BaNi₂V₂O₈-BaNi₂P₂O₈ layered honeycomb spin-1 system is reported. A change from dominantly 2-dimensional (2D) to dominantly 3-dimentional (3D) magnetic character is observed on progressing from the pure V to the pure P material. The change is continuous with composition in BaNi₂(V_1?xP_x)₂O₈. But a variety of features in the temperature-dependent magnetic susceptibilities at low temperatures suggest that the magnetic system is complex. Although the Curie–Weiss temperature becomes less strongly negative on increasing the P content, an indication of increased competition between different types of magnetic coupling, the system does not appear to be approaching a quantum spin liquid state at low temperatures.     

A tunable spatial spin splitter based on a spin–orbit-coupling modulated magnetic nanostructure

We investigate theoretically the spin-dependent Goos–Hänchen (GH) effect in a magnetic nanostructure modulated by spin–orbit coupling (SOC), which can be experimentally realized by depositing a ferromagnetic (FM) stripe and a Schottky-metal (SM) stripe on the top and bottom of an InAs/Al_xIn_1?xAs heterostructure, respectively. We consider two kinds of different SOCs (Rashba and Dresselhaus types), and calculate the GH shift and its spin polarization for the electrons across the device. Results show that the GH shift still is spin-polarized after including the SOC, and the behavior of the spin-polarized electrons can be manipulated by the Rashba and/or Dresselhaus SOC. These interesting properties provide an alternative scheme for spatially realizing spin injection into a semiconductor, and the magnetic nanostructure can be employed as a controllable spatial spin splitter for a spin-polarized source in spintronics.     

Conductance dips and spin precession in a nonuniform waveguide with spin–orbit coupling

An infinite waveguide with a nonuniformity, a segment of finite length with spin–orbit coupling, is considered in the case when the Rashba and Dresselhaus parameters are identical. Analytical expressions have been derived in the single-mode approximation for the conductance of the system for an arbitrary initial spin state. Based on numerical calculations with several size quantization modes, we have detected and described the conductance dips arising when the waves are localized in the nonuniformity due to the formation of an effective potential well in it. We show that allowance for the evanescent modes under carrier spin precession in an effective magnetic field does not lead to a change in the direction of the average spin vector at the output of the system.     

Thermodynamics of a spin 1/2 Anderson impurity in theU→∞ limit

The Bethe-ansatz equations describing the thermodynamics of the non-degenerate Anderson model are derived in theU limit (double occupation of the localized level is excluded). The set of Bethe-ansatz equations for theU limit is considerably different from the one for the finiteU case. The Kondo limit, the Fermi liquid behavior at lowT and the highT perturbation expansion for the thermodynamic potential are extracted from these equations.Heisenberg-fellow of the Deutsche Forschungsgemeinschaft     

Thermally induced spin polarization and thermal conductivities in a spin–orbit-coupled two-dimensional electron gas

The thermal conductivities and spin polarization induced by the temperature gradient are investigated in a Rashba spin–orbit-coupled two-dimensional electron gas. In this spin–orbit-coupled system in the presence of nonmagnetic or magnetic electron–impurity scattering, the Wiedemann–Franz law still holds. However, the spin polarization induced by the temperature gradient strongly depends on the property of impurities. The components of spin accumulation both perpendicular and parallel to the direction of the temperature gradient, and the thermally induced charge Hall conductivity may be nonzero for magnetic disorders.     

Persistent spin current in a quantum wire with weak Dresselhaus spin——orbit coupling

The spin current in a parabolically confined semiconductor heterojunction quantum wire with Dresselhaus spin--orbit coupling is theoretically studied by using the perturbation method. The formulae of the elements for linear and angular spin current densities are derived by using the recent definition for spin current based on spin continuity equation. It is found that the spin current in this Dresselhaus spin--orbit coupling quantum wire is antisymmetrical, which is different from that in Rashba model due to the difference in symmetry between these two models. Some numerical examples for the result are also demonstrated and discussed.     

Time-resolved spin dynamics in strained Zn1−xMnxSe/ZnSe spin superlattices

We use time-resolved spectroscopy to directly compare the spin dynamics in strained ZnMnSe epilayers and strained ZnMnSe/ZnSe spin superlattices. The spin-relaxation in these materials is observed to depend strongly on the concentration of the magnetic impurities. Surprisingly, however, no difference is observed between the spin-relaxation of excitons in the quasi-three-dimensional epilayers or the two-dimensional spin superlattices. Indeed, the spin-relaxation of excitons is also seen to be independent of the applied magnetic field or magnetization of the Mn-impurities.     

Hysteretic behavior of quadrupolar ordering in a 2D magnetic spin˗1 Ising nanoparticle

Pair approximation technique has been used to study the quadrupolar ordering properties for the 2D magnetic spin-1 Ising nanoparticles, consisting of core and surface parts with an interface coupling. Similar to the magnetic hysteresis, it has been shown that the quadrupole order parameter (Q) as a function of single-ion anisotropy (D) has a ‘hysteresis’ character which is generally called quadrupole (or QD) hysteresis. The observed QD loops strongly depend on temperature (T), external magnetic field (H) and biquadratic exchange interaction (K). Shifted QD loops with an asymmetry are found when H and K values are increased. These behaviors are also discussed in relation to other theoretical findings.     

Interaction and spin–orbit effects on a kagome lattice at 1/3 filling

We investigate the competing effects of spin-orbit coupling and electron--electron interaction on a kagome lattice at 1/3 filling. We apply the cellular dynamical mean-field theory and its real-space extension combined with the continuous time quantum Monte Carlo method, and obtain a phase diagram including the effects of the interaction and the spin-orbit coupling at T = 0. 1t, where T is the temperature and t is the hopping energy. We find that without the spin-orbit coupling, the system is in a semi-metal phase stable against the electron--electron interaction. The presence of the spin-orbit coupling can induce a topological non-trivial gap and drive the system to a topological insulator, and as the interaction increases, a larger spin--orbit coupling is required to reach the topological insulating phase.     

Pseudoscalar Cornell potential for a spin- 1/2 particle under spin and pseudospin symmetries in 1 ＋ 1 dimension

The Cornell potential that consists of Coulomb and linear potentials has received a great deal of attention in particle physics. In this paper, we present the exact solutions of the Dirac equation with the pseudoscalar Cornell potential under spin and pseudospin symmetry limits. The energy eigenvalues and corresponding eigenfunctions are given in closed form.     

Decoherence from a spin chain with Dzyaloshinskii—Moriya interaction

We study the dynamics of quantum discord and entanglement for two spin qubits coupled to a spin chain with Dzyaloshinsky-Moriya interaction.In the case of a two-qubit with an initial pure state,quantum correlations decay to zero at the critical point of the environment in a very short time.In the case of a two-qubit with initial mixed state,it is found that quantum discord may get maximized due to the quantum critical behavior of the environment,while entanglement vanishes under the same condition.Besides,we observed a sudden transition between classical and quantum decoherence when only a single qubit interacts with the environment.The effects of Dzyaloshinsky-Moriya interaction on quantum correlations are considered in the two cases.The decay of quantum correlations is always strengthened by Dzyaloshinsky-Moriya interaction.     

Neutron spin quantum plasmas – Ferromagnetism as a relaxed state

It is shown that a ferromagnetic “minimum energy relaxed state” is accessible to a neutron fluid. We model the neutron fluid as a spin quantum plasma where the electromagnetic interaction is trough the magnetic moment of the neutron. The neutron ferromagnetism results from the macroscopic spin alignment that occurs due to a profound interplay between the classical and spin quantum vorticities carried by the charge-less neutron fluid. The simplest manifestation of a neutron superfluidity comes about by an exact cancellation of the quantum and classical vorticities to create a helicity free system.     

Can a linearly polarized light beam polarize atomic spin?

Lax et al. [Phys. Rev. 11 (1975) 1365] discovered that a light beam in vacuum is not a transverse wave but does have a longitudinal field component. We investigate atomic and molecular electric dipole transitions induced by such a light beam, in particular, linearly polarized in a transverse plane. We derive the selection rules and the transition rates for various quantization axes using the paraxial approximation up to the first order of 1/kw, where k is the wave number and w is the transverse size of the light beam. The light beam is able to yield atomic spin polarization in the direction perpendicular to both the optical axis and the transverse electric field, and its magnitude is approximately 1/kw times that generated by a circularly polarized light wave with the similar intensity.     

Dynamics of bright soliton in a spin–orbit coupled spin-1 Bose–Einstein condensate

We have investigated the dynamics of bright solitons in a spin–orbit coupled spin-1 Bose–Einstein condensate analytically and numerically. By using the hyperbolic sine function as the trial function to describe a plane wave bright soliton with a single finite momentum, we have derived the motion equations of soliton's spin and center of mass, and obtained its exact analytical solutions. Our results show that the spin–orbit coupling couples the soliton's spin with its center-of-mass motion, the spin oscillations induced by the exchange of atoms between components result in the periodical oscillation of center-of-mass, and the motion of center of mass of soliton can be viewed as a superposition of periodical and linear motions. Our analytical results have also been confirmed by the direct numerical simulations of Gross–Pitaevskii equations.     

Mössbauer spectroscopy monitoring the spin transition of a FeII 1D chain with a fluorinated 4-R-1,2,4-triazole

The spin transition properties of [Fe(fletrz)₃](BF₄)₂?2H₂O are described. Fletrz (4-(2’-fluoroethyl)-4H-1,2,4-triazole) is a novel fluorine substituted 1,2,4-triazole ligand which forms 1D chain upon self-assembly with Fe^II ions. This coordination polymer exhibits reversible abrupt thermochromic spin transition that has been probed by SQUID magnetometry, variable temperature ⁵⁷Fe Mossbauer spectroscopy (77–300 K) and differential scanning calorimetry (100–300 K).     

Ground-states and rotational properties of a spin–orbit-coupled spin-1 Bose–Einstein condensate in a concentrically coupled toroidal trap

We investigate the ground states of an antiferromagnetic spin-1 Bose–Einstein condensate with spin–orbit coupling in a concentrically coupled toroidal trap. A new necklace-type state with double-ring structure is created in the system due to the spin–orbit coupling. The petal number of the necklace state is increased with enhancing the strength of the spin–orbit coupling. When the rotation is introduced, the condensate can be dragged into the outer trough of the trap by increasing the rotation frequency, which makes it possible to realize the exotic ground state combined by the necklace state at the inner trough and the persistent flow at the outer one. Once the two troughs of the toroidal trap are populated by the persistent flow at the specific effective interactions between atoms, the hidden vortices may occur in the central region of the trap and at the barrier between the two troughs. In addition, the visible vortex with the laminar structure can be generated under the more effective atomic interaction.     

Characteristics of persistent spin current components in a quasi-periodic Fibonacci ring with spin–orbit interactions: Prediction of spin–orbit coupling and on-site energy

In the present work we investigate the behavior of all three components of persistent spin current in a quasi-periodic Fibonacci ring subjected to Rashba and Dresselhaus spin–orbit interactions. Analogous to persistent charge current in a conducting ring where electrons gain a Berry phase in presence of magnetic flux, spin Berry phase is associated during the motion of electrons in presence of a spin–orbit field which is responsible for the generation of spin current. The interplay between two spin–orbit fields along with quasi-periodic Fibonacci sequence on persistent spin current is described elaborately, and from our analysis, we can estimate the strength of any one of two spin–orbit couplings together with on-site energy, provided the other is known.