Edge spin currents in two-dimensional electron gas with spin-orbit interaction

Edge spin currents existing in two-dimensional electron gas near the boundary between the regions with spin-orbit interaction and without it are st udied for nonequilibrium conditions due to an electron current flowing parallel or normal to the boundary. The parallel current generates an edge spin density, whereas the normal one changes the edge spin current by a value proportional to the particle current.     

Zero-field spin splitting in a two-dimensional electron gas with the spin-orbit interaction revisited

We consider a two-dimensional electron gas (2DEG) with the Rashba spin-orbit interaction (SOI) in the presence of a perpendicular magnetic field. We derive analytical expressions of the density of states (DOS) of a 2DEG with the Rashba SOI in the presence of a magnetic field by using the Green's function technique. The DOS allows us to obtain the analytical expressions of the magnetoconductivities for spin-up and spin-down electrons. The conductivities for spin-up and spin-down electrons oscillate with different frequencies and give rise to the beating patterns in the amplitude of the Shubnikov-de Haas (SdH) oscillations. We find a simple equation which determines the zero-field spin splitting energy if the magnetic field corresponding to any beat node is known from the experiment. Our analytical results reproduce well the experimentally observed non-periodic beating patterns, number of oscillations between two successive nodes and the measured zero-field spin splitting energy.     

Magnetotransport properties of a magnetically modulated two-dimensional electron gas with the spin-orbit interaction

We study the electrical transport properties of a two-dimensional electron gas (2DEG) with the Rashba spin-orbit interaction in the presence of a constant perpendicular magnetic field (B(0)( ?z) which is weakly modulated by B1 = B1 cos(qx) ?z, where B(1) ? B(0) and q = 2π/a with a the modulation period. We obtain the analytical expressions of the diffusive conductivities for spin-up and spin-down electrons. The conductivities for spin-up and spin-down electrons oscillate with different frequencies and produce beating patterns in the amplitude of the Weiss and Shubnikov-de Haas oscillations. We show that the Rashba strength can be determined by analyzing the beating pattern in the Weiss oscillation. We find a simple equation which determines the Rashba spin-orbit interaction strength if the number of Weiss oscillations between any two successive nodes is known from the experiment. We compare our results with the electrically modulated 2DEG with the Rashba interaction. For completeness, we also study the beating pattern formation in the collisional and the Hall conductivities.     

Anomalous Hall effect in a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interaction

We discuss the mechanism of the anomalous Hall effect in a Rashba-Dresselhaus two-dimensional electron gas subjected to a homogeneous out-of-plane magnetization. On the basis of a systematic treatment of the kinetic equations for the spin-density matrix, results are derived for the dynamic Hall conductivity in a closed form. Its nonanalytic dependence on both the scattering time and the frequency of the applied electric field is discussed. Except for in a special Rashba-Dresselhaus model, there is a finite intrinsic anomalous Hall effect, which is extremely sensitive to short-range elastic scattering.     

Optical conductivity of a two-dimensional electron liquid with spin-orbit interaction

The interplay of electron-electron interactions and spin-orbit coupling leads to a new contribution to the homogeneous optical conductivity of the electron liquid. The latter is known to be insensitive to many-body effects for a conventional electron system with parabolic dispersion. The parabolic spectrum has its origin in the Galilean invariance which is broken by spin-orbit coupling. This opens up a possibility for the optical conductivity to probe electron-electron interactions. We analyze the interplay of interactions and spin-orbit coupling and obtain optical conductivity beyond RPA.     

Tunneling conductance of a two-dimensional electron gas with Dresselhaus spin-orbit coupling

We theoretically studied the spin-dependent charge transport in a two-dimensional electron gas with Dresselhaus spin-orbit coupling (DSOC) and metal junctions. It is shown that the DSOC energy can be directly measured from the tunneling conductance spectrum. We found that spin polarization of the conductance in the propagation direction can be obtained by injecting from the DSOC system. We also considered the effect of the interfacial scattering barrier (both spin-flip and non-spin-flip scattering) on the overall conductance and the spin polarization of the conductance. It is found that the increase of spin-flip scattering can enhance the conductance under certain conditions. Moreover, both types of scattering can increase the spin polarization below the branches crossing of the energy band.     

Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.     

Magnetic moment of a 2D electron gas with spin-orbit interaction

An explicit analytic expression is derived for the magnetic moment of a 2D electron gas taking into account the spin-orbit interaction in the Rashba model with T = 0. The cases of constant chemical potential and number of electrons are investigated. The magnetic field and temperature dependences of the magnetic moment are analyzed. The results are compared with the results of experimental studies of magnetization.     

Magnetoplasma oscillations of a two-dimensional electron system with spin-orbit interaction in a lateral superlattice

Low-frequency magnetoplasmon modes in a one-dimensional lateral superlattice with Rashba spin-orbit splitting are considered. Such modes correspond to oscillations related to virtual transitions within a Landau level that become possible due to the broadening of each Landau level into a band produced by the superlattice potential. The specificity of the one-dimensional intersubband plasmons emerging in such a system has been revealed.     

Electron spin precession in two-dimensional electron gas with Rashba spin-orbit coupling

Using the time-dependent Schrödinger equation, we present the analytical result of the expectation value of spin injected into a two-dimensional electron gas with respect to an arbitrarily spin-polarized electron state and monitor the spin time-evolution. We demonstrate that the expectation value of spin operator Sx is the time-independent, and only the expectation values in the Sy-Sz plane are time-dependent. A detailed study of spin precession in the spin-valve and spin-transistor geometry is presented, in which the initial spin-polarized electron state point perpendicular and parallel to the current direction, respectively. We put forward the possible reason that the resistance change is independent of gate voltage in the spin-valve geometry. Furthermore, it has been shown that the effective magnetic field generated by the spin-orbit interaction is not same with the truly magnetic field. The main effect of the truly magnetic field is to align the spin along the field direction, but the effective magnetic field generated by the spin-orbit interaction does not.     

Magnetoquantum transport in a modulated 2D electron gas with spin-orbit interaction

We investigate the effects of spin-orbit interaction (SOI) and plane-perpendicular magnetic field on the conductivity of a two-dimensional electron system in the presence of one-dimensional electrostatic modulation. The calculations are performed when a low-intensity, low-frequency external electric field is applied. The Kubo formula for the conductivity is employed in the calculation. The single-particle eigenstates which depend on the strengths of the magnetic field, the SOI and modulation potential, are calculated and then used to determine the conductivity. We present numerical results for the conductivity along the channels as well as the tunneling conductivity perpendicular to the constrictions as functions of the modulation potential, the SOI and the magnetic field. We demonstrate that the effect of finite frequency is to related to the reduction of both the longitudinal and transverse conductivities.     

Quantum Hall effect in a two-dimensional electron gas with spin-orbit coupling in the field of a surface superlattice

The Hall conductance of a two-dimensional electronic system with Rashba spin-orbit coupling in the presence of an external periodic potential of a superlattice and a perpendicular magnetic field has been calculated. The calculations were performed for an electron gas with parameters typical both of a system with weak spin-orbit coupling (AlGaAs/GaAs) and a system with relatively strong Rashba coupling (InGaAs/InAs).     

Vertex corrections to the anomalous Hall effect in spin-polarized two-dimensional electron gases with a Rashba spin-orbit interaction

We study the effect of disorder on the intrinsic anomalous Hall conductivity in a magnetic two-dimensional electron gas with a Rashba-type spin-orbit interaction. We find that anomalous Hall conductivity vanishes unless the lifetime is spin-dependent, similar to the spin Hall conductivity in the nonmagnetic system. In addition, we find that the spin Hall conductivity does not vanish in the presence of magnetic scatterers.     

Universal spin-induced time reversal symmetry breaking in two-dimensional electron gases with Rashba spin-orbit interaction

We have experimentally studied the spin-induced time reversal symmetry (TRS) breaking as a function of the relative strength of the Zeeman energy (E(Z)) and the Rashba spin-orbit interaction energy (E(SOI)), in InGaAs-based 2D electron gases. We find that the TRS breaking, and hence the associated dephasing time tau(phi)(B), saturates when E(Z) becomes comparable to E(SOI). Moreover, we show that the spin-induced TRS breaking mechanism is a universal function of the ratio E(Z)/E(SOI), within the experimental accuracy.     

Oscillations of the kinetic coefficients in a two-dimensional electron system with the spin-orbit interaction in an alternating magnetic field

The response of a two-dimensional electron system with the spin-orbit interaction to a measuring direct-current electric field is investigated for the case in which the system is disturbed from the equilibrium by a microwave alternating magnetic field. Point nonmagnetic impurities are considered as scattering sources. It is demonstrated that the combined transitions occurring under the action of an alternating magnetic field lead to new oscillations of the diagonal components of the electrical conductivity tensor of the two-dimensional electron gas.     

Electron-dephasing time in a two-dimensional spin-polarized system with Rashba spin-orbit interaction

We calculate the dephasing time tau(phi)(B) of an electron in a two-dimensional system with a Rashba spin-orbit interaction, spin-polarized by an arbitrarily large magnetic field parallel to the layer. tau(phi)(B) is estimated from the logarithmic corrections to the conductivity within a perturbative approach that assumes weak, isotropic disorder scattering. For any value of the magnetic field, the dephasing rate changes with respect to its unpolarized-state value by a universal function whose parameter is 2E(Z)/E(SOI) (E(Z) is the Zeeman energy, while E(SOI) is the spin-orbit interaction), confirming the experimental report published in Phys. Rev. Lett. 94, 186805 (2005). In the high-field limit, when 2E(Z) > E(SOI), the dephasing rate saturates and reaches asymptotically to a value equal to half the spin-relaxation rate.     

Magnetic impurities in a two-dimensional superfluid Fermi gas with spin-orbit coupling

We study magnetic impurities in a two dimensional superfluid Fermi gas with thespin-orbit coupling and find that the spin-orbit coupling makes some dramatic impacts onthe effects of magnetic impurities. For the single impurity problem, we find that thenumber of bound states localized around the magnetic impurity is doubled. For the finiteconcentration n of impurities, we find that the energy gap is reduced andthe density of states in the gapless region is greatly modified; there exists a gaplesssuperfluid and N(ω) ∝ ω in the smallω limit.     

Coherent quantum transport in two-dimensional electron gas/superconductor double junctions with Rashba spin-orbit coupling

Based on the extended Blonder-Tinkham-Klapwijk (BTK) approach, we have investigated the coherent quantum transport in two-dimensional electron gas/superconductor (2DEG/SC) double tunneling junctions in the presence of the Rashba spin-orbit coupling (RSOC). It is found that all the reflection coefficients in BTK theory as well as conductance spectra oscillate with the external voltage and energy. The oscillation feature of conductance can be tuned largely by the RSOC for low insulating barriers, while for high insulating barriers it is almost independent of the RSOC. These phenomena are essentially different from those found in ferromagnet/superconductor double tunneling junctions.     

Wigner function of a two-dimensional electron gas in a magnetic field

The Wigner function of a two-dimensional electron gas in an arbitrary magnetic field perpendicular to the plane in which the electrons are confined is constructed rigorously. The function is useful in taking various statistical averages and illuminates the roles played by the hyperbolic functions of the field which appear in the expressions of the susceptibility and other physical quantities.