Exact and quasiclassical Green's functions of two-dimensional electron gas with Rashba–Dresselhaus spin–orbit interaction in parallel magnetic field

New exact and asymptotical results for the one particle Green's function of 2D electrons with combined Rashba–Dresselhaus spin–orbit interaction in the presence of in-plane uniform magnetic field are presented. A special case that allows an exact analytical solution is also highlighted. To demonstrate the advantages of our approach we apply the obtained Green's function to calculation of electron density and magnetization.     

Effects of external magnetic field on the electron Zitterbewegung in the quantum dots and wires with Rashba spin–orbit interaction

We study in this article the effects of external magnetic field on the electron Zitterbewegung in semiconductor quantum dots and wires with parabolic confinements and Rashba spin–orbit interaction. In doing so, we have calculated the dynamics of the expectation value of the position operator by means of the time evolution operator in an appropriate Hilbert space. The results show that the electron Zitterbewegung, its amplitude which is related to the electron confinement, and the period of the electron Zitterbewegung depend on the external magnetic field. We propose that the magnetic field can be used as an external agent to control the electron Zitterbewegung, a fundamental key for experimental detection of this phenomena.     

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.     

Symmetry and optical transition rule for low-dimensional semiconductor system with spin–orbit interaction and magnetic field

Starting from effective mass Hamiltonian, we systematically investigate the symmetry of low-dimensional structures with spin–orbit interaction and transverse magnetic field. The position-dependent potentials are assumed to be space symmetric, which is ever-present in theory and experiment research. By group theory, we analyze degeneracy in different cases. Spin–orbit interaction makes the transition between Zeeman sub-levels possible, which is originally forbidden within dipole approximation. However, a transition rule given in this paper for the first time shows that the transition between some levels is forbidden for space symmetric potentials.     

Anomalous spin–orbit coupling in high-density two-dimensional electron gas confined in InGaAs/InAlAs quantum well

We study the magnetotransport property of a high-density two-dimensional electron gas confined in InGaAs/InAlAs quantum well. Both beating pattern in the Shubnikov–de Hass oscillation of resistivity and weak antilocalization effect are observed. From these two effects, Rashba spin-splitting energy is extracted. The extracted Rashba spin-splitting energy shows a nonmonotonic dependence on Fermi wave vector, contrary to the prevailing linear Rashba model. This anomalous behavior can be attributed to the nonlinear Rashba spin-splitting mechanism [Yang et al., Phys. Rev. B 74 (2006) 193314].     

Quasiparticle lifetime of electron–electron interactions for two-dimensional electron gases with magnetic field

We theoretically study the electron–electron scattering rate τ_ee⁻¹for electrons in a two-dimensional electron gas with a perpendicular magnetic field, within theGWand plasmon-pole approximations, as functions of temperatureT, impurity scattering rate Γ and magnetic fieldB. The τ_ee⁻¹increases with increasingTand increasing Γ, and shows the structure of the Landau levels asBis changed.     

Angular dependent study on spin transport in magnetic semiconductor heterostructures with Dresselhaus spin–orbit interaction

We investigate theoretically the effects of Dresselhaus spin–orbit coupling (DSOC) on the spin-dependent current and shot noise through II–VI diluted magnetic semiconductor/nonmagnetic semiconductor (DMS/NMS) barrier structures. The calculation of transmission probability is based on an effective mass quantum-mechanical approach in the presence of an external magnetic field applied along the growth direction of the junction and also applied voltage. We also study the dependence of spin-dependent properties on external magnetic field and relative angle between the magnetizations of two DMS layers in CdTe/CdMnTe heterostructures by including the DSOC effect. The results show that the DSOC has great different influence on transport properties of electrons with spin up and spin down in the considered system and this aspect may be utilized in designing new spintronics devices.     

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-polarized currents in a two-terminal quantum ring with spin–orbit interaction

Photoinduced spin current is calculated in a system consisting of a 1D quantum ring with conductors connected to it. It is shown that in the presence of Rashba’s spin–orbit interaction, a current is induced in the ring by circularly polarized radiation. Expressions are derived for the current and electron transmission coefficients taking into account the inelastic interaction with the radiation. It is shown that the spin current is a complex function of the magnetic flux through the ring, radiation frequency, and the spin–orbit coupling constant. In the presence of a potential difference, the interaction with radiation may considerably increase the efficiency of the quantum-ring-based spin filter.     

Effect of in-plane magnetic field on spin polarization in the presence of the Dresselhaus spin–orbit effect

In this paper, we theoretically study the effect of the in-plane magnetic field on spin polarization in the presence of the Dresselhaus spin–orbit effect. It is shown that the large spin polarization can be achieved in such a nanostructure due to the effects of both the Dresselhaus spin–orbit term and the in-plane magnetic field, but the latter plays a main role in the tunneling process. It is also shown that with the increase of in-plane magnetic field, the degree of spin splitting obviously becomes larger.     

Effects of Rashba spin–orbit coupling and a magnetic field on a polygonal quantum ring

Using standard quantum network method, we analytically investigate the effect of Rashba spin–orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer–Büttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain.     

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.     

Sum frequency generation in the spherical quantum dots in the presence of applied electric field and spin–orbit interaction

The sum-frequency generation (SFG) is theoretically studied in a quantum dot (QD) through the framework of the effective-mass approximation and compact density matrix approach. QD is spherical with the parabolic potential confinement, under applied electric field and in the presence of Rashba spin-orbit interaction (SOI). Using the computed energies and eigenkets, the second-order susceptibility of SFG has been also calculated as a function of radius of QD, spin–orbit interaction strength and the applied electric field. The effects of Rashba SOI strength, radius of QD and the applied electric field on the second-order of susceptibility coefficient are considered.     

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.     

Spin Hall effect and spin current generation in two-dimensional systems with random Rashba spin–orbit coupling

We consider a new effect induced by spin–orbit coupling in a two-dimensional electron gas confined in a semiconductor quantum well, i.e. the possibility of spin current generation by fluctuating random Rashba spin–orbit interaction, with the corresponding mean value of the interaction being equal to zero. Our main results suggest that – in contrast to the spatially uniform Rashba spin–orbit interaction – the spin Hall effect does not vanish for typical disorder strengths. We also point out some other possibilities of using such a random Rashba coupling for the generation of spin density and spin current in two-dimensional nonmagnetic structures.     

Effective period potential in a hybrid mesoscopic ring with Rashba spin–orbit interaction

We investigate theoretically the persistent charge current (PCC) and pure spin current (PSC) in a hybrid mesoscopic ring with Rashba spin–orbit interaction (RSOI). The PCC and PSC surviving in the ring would experience a periodic potential formed by the band offset of the constituent materials. Similarly, an effective tunnel barrier can be introduced by a region with different RSOI strength. This provides us a convenient way to manipulate the periodic potential by changing the RSOI strength through an electric field. With the increment of the RSOI strength, the PCC is suppressed, while the PSC presents an oscillatory pattern changing from negative to positive.     

Transport properties of the two-dimensional electron gas in AlP quantum wells at finite temperature including magnetic field and exchange–correlation effects

We investigate the transport scattering time, the single-particle relaxation time and the magnetoresistance of a quasi-two-dimensional electron gas in a GaP/AlP/GaP quantum well at zero and finite temperatures. We consider the interface-roughness and impurity scattering, and study the dependence of the mobility, scattering time and magnetoresistance on the carrier density, temperature and local-field correction. In the case of zero temperature and Hubbard local-field correction our results reduce to those of Gold and Marty (Physica E 40 (2008) 2028; Phys. Rev. B 76 (2007) 165309). We also discuss the possibility of a metal–insulator transition which might happen at low density.     

Combined exciton–electron excitation in quantum wells with a two-dimensional electron gas of low density

A combined exciton–cyclotron resonance is found in the photoluminescence excitation and reflectivity spectra of semiconductor quantum wells with an electron gas of low density. In external magnetic fields an incident photon creates an exciton in the ground state and simultaneously excites an electron between Landau levels. A theoretical model is developed and suggests the dominating contribution of the exchange exciton–electron interaction.     

Thermoelectric transport and spin density of graphene nanoribbons with Rashba spin–orbit interaction

In the present paper, we have theoretically investigated thermoelectric transport properties of armchair and zigzag graphene nanoribbons with Rashba spin–orbit interaction, as well as dephasing scattering processes by applying the nonequilibrium Green function method. Behaviors of electronic and thermal currents, as well as thermoelectric coefficients are studied. It is found that both electronic and thermal currents decrease, and thermoelectric properties been suppressed, with increasing strength of Rashba spin–orbit interaction. We have also studied spin split and spin density induced by Rashba spin–orbit interaction in the graphene nanoribbons.     

Spin-dependent transport through a serial double-quantum-dot with Rashba spin–orbit interaction

We study the spin-dependent electron transport through a serial double-quantum-dot (DQD) by using Green’s function equation of motion technique. Special attention is paid to the functions of the Rashba spin–orbit (RSO) effect in one of the DQD and the inter-dot tunneling coupling _tc$t_c$. When the electrons transport from the left or the right lead into the middle lead, a quasi-two channel is established due to the existence of _tc$t_c$. Then, the RSO interaction will induce into the tunnel matrix element a spin-dependent extra phase factor σ_?R$\sigma {?}_R$ as the electrons flowing through different conduction channels, and thus making the current in the middle lead to be spin-polarized. Moreover, by properly adjusting the value of _tc$t_c$, the dot-lead coupling strength, dots’ levels and the external bias voltages, a net spin current without the accompanying of charge current can be generated. The structure proposed here is simple and can be realized in the present experiments.