Spin Accumulation in a Rashba Nanoribbon

We investigate theoretically the spin accumulation in a Rashba spin-orbit coupling （SOC） nanoribbon nonadiabatically connected to a normal conductor. Both the nanoribbon and conductor are described by a hard-wall confining potential. Using the scattering matrix approach within the effective free-electron approximation, we have calculated the out-of-plane spin accumulation in the nanoribbon. It is found that the spin accumulation shifts toward the two edges of nanoribbon with the increasing of propagation modes. Specifically, as the Rashba SOC strength increases the spin accumulation in the nanoribbon will be enhanced and this result may suggest us a simple method to control the spin accumulation of the system by Rashba SOC strength.     

Spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling

Using the perturbation method,we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling.The heat generated by the spin current is calculated.With the increase of the width of the quantum wire,the spin current and the heat generated both exhibit period oscillations with equal amplitudes.When the quantum-channel number is doubled,the oscillation periods of the spin current and of the heat generated both decrease by a factor of 2.For the spin current j s,xy,the amplitude increases with the decrease of the quantum channel;while the amplitude of the spin current j s,yx remains the same.Therefore we conclude that the effect of the quantum-channel number on the spin current j s,xy is greater than that on the spin current j s,yx.The strength of the Rashba spin-orbit coupling is tunable by the gate voltage,and the gate voltage can be varied experimentally,which implies a new method of detecting the spin current.In addition,we can control the amplitude and the oscillation period of the spin current by controlling the number of the quantum channels.All these characteristics of the spin current will be very important for detecting and controlling the spin current,and especially for designing new spintronic devices in the future.     

Manipulation of Persistent Spin Helix States by Weak External Magnetic Fields

We study theoretically the effect of weak external magnetic fields on persistent spin helix states in semi- conductor two-dimensional electron gases with both Rashba and linear-in-momentum Dresselhaus spin-orbit coupling. We show that in the presence of weak external magnetic fields, some basic properties of a persistent spin helix state, including the dispersion relation between the decay time and the magnitude of the wavevector, the maximum decay time and the value of the characteristic magnitude of the wavevector at which the maximum decay time occurs, will all depend sensitively on the directions of applied external magnetic fields.     

Theory of phonon-modulated electron spin relaxation time based on the projection reduction method

This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature （T） dependence of electron spin relaxation times （T1） in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field （B） dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.     

The effects of Dresselhaus and Rashba spin-orbit interactions on the electron tunneling in a non-magnetic heterostructure

We theoretically investigate the electron transport properties in a non-magnetic heterostructure with both Dresselhaus and Rashba spin-orbit interactions. The detailed-numerical results show that (1) the large spin polarization can be achieved due to Dresselhaus and Rashba spin-orbit couplings induced splitting of the resonant level, although the magnetic field is zero in such a structure, (2) the Rashba spin-orbit coupling plays a greater role on the spin polarization than the Dresselhaus spin-orbit interaction does, and (3) the transmission probability and the spin polarization both periodically change with the increase of the well width.     

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.     

Ground state of rotating ultracold quantum gases with anisotropic spin orbit coupling and concentrically coupled annular potential

Motivated by recent experimental realization of synthetic spin–orbit coupling in neutral quantum gases, we consider the quasi-two-dimensional rotating two-component Bose–Einstein condensates with anisotropic Rashba spin–orbit coupling subject to concentrically coupled annular potential. For experimentally feasible parameters, the rotating condensate exhibits a variety of rich ground state structures by varying the strengths of the spin–orbit coupling and rotational frequency.Moreover, the phase transitions between different ground state phases induced by the anisotropic spin–orbit coupling are obviously different from the isotropic one.     

B~3Σ_u~- X~3Σ_g~- transition in selenium dimer:ab initio multireference configuration interaction calculations

Theoretical investigation of low-lying electronic states and B 3Σu-X3Σg- transition properties of selenium dimer using size-extensivity singly and doubly excitation multireference configuration interaction theory with nonrelativistic all-electron basis set and relativistic effective core potential plus its split valence basis set is presented in this paper. The spectroscopic constants of ten low-lying Λ-S bound states have been obtained and compared with experiments. Spin-orbit calculations for coupling between B3Σu- sates and repulsive 1Πu,5Πu states have been made to interpret the predissociation mechanisms of the B3Σu- state. The lifetimes of B3Σu-(ν=0～6) have been calculated with scalar relativistic effects included or excluded,respectively,and reasonably agree with experimental values.     

Zero field spin splitting in asymmetric quantum wells

Spin splitting of asymmetric quantum wells is theoretically investigated in the absence of any electric field, including the contribution of interface-related Rashba spin-orbit interaction as well as linear and cubic Dresselhaus spin-orbit interaction. The effect of interface asymmetry on three types of spin-orbit interaction is discussed. The results show that interface-related Rashba and linear Dresselhaus spin-orbit interaction can be increased and cubic Dresselhaus spin-orbit interaction can be decreased by well structure design. For wide quantum wells, the cubic Dresselhaus spin-orbit interaction dominates under certain conditions, resulting in decreased spin relaxation time.     

Spin texturing in quantum wires with Rashba and Dresselhaus spin–orbit interactions and in-plane magnetic field

In this work, we investigate the effects of interplay of spin–orbit interaction and in-plane magnetic fields on the electronic structure and spin texturing of parabolically confined quantum wire. Numerical results reveal that the competing effects between Rashba and Dresselhaus spin–orbit interactions and the external magnetic field lead to a complicated energy spectrum. We find that the spin texturing owing to the coupling between subbands can be modified by the strength of spin–orbit couplings as well as the magnitude and the orientation angle of the external magnetic field.     

Spin transport in a chain of polygonal quantum rings with Dresselhaus spin-orbit coupling

Using a transfer matrix method, we investigate spin transport through a chain of polygonal rings with Dresselhaus spin-orbit coupling(DSOC). The spin conductance is dependent on the number of sides in the polygons. When DSOC is considered in a chain which also has Rashba spin-orbit coupling(RSOC) of the same magnitude, the total conductance is the same as that for the same chain with no SOC. However, when the two types of SOC have different values, there results a unique anisotropic conductance.     

Acoustic phonons mediated non-equilibrium spin current in the presence of Rashba and Dresselhaus spin–orbit couplings

Influence of electrons interaction with longitudinal acoustic phonons on magnetoelectric and spin-related transport effects are investigated. The considered system is a two-dimensional electron gas system with both Rashba and Dresselhaus spin–orbit couplings. The works which have previously been performed in this field, have revealed that the Rashba and Dresselhaus couplings cannot be responsible for spin current in the non-equilibrium regime. In the current Letter, a semiclassical method was employed using the Boltzmann approach and it was shown that the spin current of the system, in general, does not go all the way to zero when the electron–phonon coupling is taken into account. It was also shown that spin accumulation of the system could be influenced by electron–phonon coupling.     

Rashba–Dresselhaus double refraction in a two-dimensional electron gas

We investigate the ballistic transport properties of an electron traversing through a two-dimensional electron gas with the Rashba and Dresselhaus spin–orbit coupling (R–D SOC) coexistent. A nonzero incident angle is considered. The relation between the transmission and the incident angle, the interfacial scattering strength, the length of the SOC region and the SOC intensity are revealed. The transmission strength decays when the incident angle is larger than a critical angle. The transport spin polarization is remarkably modulated by the coaction of the two types of SOC.     

Intersubband spin-orbit coupling and spin splitting in symmetric quantum wells

In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to the well-known Dresselhaus and Rashba effects. If one considers quantum wells with two or more conduction subbands, an additional, intersubband-induced spin-orbit term appears whose strength is comparable to the Rashba coupling, and which remains finite for symmetric structures. We show that the conduction band spin splitting due to this intersubband spin-orbit coupling term is negligible for typical III-V quantum wells.     

Spin Splitting in Different Semiconductor Quantum Wells

We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field. The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included. The results show that the structure of quantum well plays an important role in spin splitting. The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different. The origin of the distinction is discussed in this work.     

Influence of spin–orbit interactions on the polaron properties in wurtzite semiconductor quantum well

We have study the simultaneous effect of Rashba and Dresselhaus spin–orbit interactions on the polaron properties in wurtzite semiconductor quantum wells. The linear and cubic contributions of the bulk Dresselhaus spin–orbit coupling and the effects of phonon confinement on electron–optical-phonon interaction Hamiltonians are taken into account. We have found analytical solutions for the polaron energies as well as polaron effective mass within the range of validity of perturbation theory. It is shown that the polaron energy and effective mass correction are both significantly enhanced by the spin–orbit coupling. Wave number dependent phonon contribution on the electron energy has minima and varies differently of the spin-up and spin-down states. Polaron self-energy due to interface optical phonon modes has larger values than of the confined optical phonon modes ones. The polaron effective mass exhibits anisotropy and the contribution of the Dresselhaus spin–orbit coupling term on the polaron effective mass is dominated by Rashba one.     

Controllable Spin Polarization of Charge Current by Rashba Spin Orbital Coupling

We report a theoretic study on modulating the spin polarization of charge current in a mesoscopic fourterminal device of cross structure by using the inverse spin hall effect. The scattering region of device is a two-dimensional electron gas （2DEG） with Rashba spin orbital interaction （RSOI）, one of lead is ferromagnetic metal and other three leads are spin-degenerate normal metals. By using Landauer-Biittiker formalism, we found that when a longitudinal charge current flows through 2DEG scattering region from FM lead by external bias, the transverse current can be either a pure spin current or full-polarized charge current due to the combined effect of spin hall effect and its inverse process, and the polarization of this transverse current can be easily controlled by several device parameters such as the Fermi energy, ferromagnetic magnetization, and the RSOI constant. Our method may pave a new way to control the spin polarization of a charge current.     

Spin-dependent electron transport in a nonmagnetic nanostructure with both Dresselhaus and Rashba spin-orbit terms

The spin-dependent electron transport is numerically studied in a nonmagnetic nanostructure in the presence of both Dresselhaus and Rashba spin-orbit interactions. It is shown that the large spin polarization can be achieved in such a structure mainly due to the Rashba spin-orbit term induced splitting of the resonant level. It is also shown that the spin polarization strongly depends on the well width and the thickness of the middle barrier as well as the height of the middle barrier.     

Orbital ac spin-Hall effect in the hopping regime

The Rashba and Dresselhaus spin-orbit interactions are both shown to yield the low temperature spin-Hall effect for strongly localized electrons coupled to phonons. A frequency-dependent electric field E(omega) generates a spin-polarization current, normal to E, due to interference of hopping paths. At zero temperature the corresponding spin-Hall conductivity is real and is proportional to omega2. At nonzero temperatures the coupling to the phonons yields an imaginary term proportional to omega. The interference also yields persistent spin currents at thermal equilibrium, at E=0. The contributions from the Dresselhaus and Rashba interactions to the interference oppose each other.     

Orbital mechanisms of electron-spin manipulation by an electric field

A theory of spin manipulation of quasi-two-dimensional (2D) electrons by a time-dependent gate voltage applied to a quantum well is developed. The Dresselhaus and Rashba spin-orbit coupling mechanisms are shown to be rather efficient for this purpose. The spin response to a perpendicular-to-plane electric field is due to a deviation from the strict 2D limit and is controlled by the ratios of the spin, cyclotron, and confinement frequencies. The dependence of this response on the magnetic field direction is indicative of the strengths of the competing spin-orbit coupling mechanisms.