Dresselhaus Spin-orbit Interaction Research Articles

Persistent current in a mesoscopic Holstein-Hubbard ring with Dresselhaus interaction

The effect of electron-phonon coupling, onsite repulsive Coulomb interaction and temperature on the persistent current in a quantum ring is studied in the presence of Dresselhaus spin-orbit interaction. The quantum ring threaded by the Aharonov-Bohm flux is modelled by the one-dimensional Holstein-Hubbard-Dresselhaus Hamiltonian. The electron-phonon interaction and Dresselhaus spin-orbit interaction are decoupled by employing the Lang-Firsov coherent transformation and a unitary transformation respectively. Thereafter, a self-consistent diagonalization technique is performed numerically at the Hartree-Fock level to obtain the effective electronic energy and current. It is shown that the intrinsic Dresselhaus spin-orbit interaction enhances the persistent charge and spin currents significantly. On the other hand, the persistent current is reduced by the onsite and nearest-neighbour electron-phonon interaction and Coulomb interaction. Also, the behaviour of the currents is modified by temperature. The spin-splitting of persistent spin current is enhanced considerably by Dresselhaus spin-orbit interaction and this splitting is tuneable in different regimes of magnetic flux, temperature, chemical potential and the interactions present in the system.

Spin-orbit interaction effects on electronic, magnetic, and optical properties of [formula omitted]- center in a quantum dot with Gaussian confinement

In this paper, we study the binding energy, transition energy, and oscillator strength of a D0 impurity positioned at the center of a two-dimensional quantum dot. The QD is subject to a Gaussian confining potential, magnetic field, Rashba, and Dresselhaus spin-orbit interactions (SOI). The ground state and first exited state energies, and corresponding binding energies are calculated. Using the variational method with simple wave functions, transition energy, magnetic moment, and susceptibilities are obtained as a function of QD parameters, magnetic field, and SOI coupling strengths. The energies and binding energies increase with Dresselhaus SOI strength but decrease with Rashba SOI strength in a magnetic field. The magnetic moment and susceptibility of both states of a (D0) impurity show diamagnetic behaviour with both SOI strengths. Finally, we studied oscillator strength and compared the available literature, which did not consider all these effects.

Crystallographic rotation effect on the particle and spin across a half metal/semiconductor junction with Dresselhaus spin-orbit interaction

Theoretical studies were conducted on probability, conductance and spin polarization through a junction between a half metal (HM)/semiconductor with Dresselhaus spin-orbit coupling (DSOC), using the scattering theory and the continuous model in a two-dimensional system. The focus was on how the bulk orientation of the DSOC affects the charge and spin polarization. Results showed that the crystal face (100) makes a negative perpendicular to the normal wave vector of the system, resulting in a maximum value of the conductance spectrum and the spin polarization. However, the maximum value of the spin polarization can occur with any crystallographic orientation when the applied voltage reaches the crossing point of the DSOC. Moreover, the electron incident angle injection can cause a gap between in the transmission probability with spin up and spin down, corresponding to higher charge and spin polarization across the junction.

Role of Rashba and Dresselhaus spin–orbit interactions on an off-center donor impurity in a Gaussian quantum dot

The Rashba and Dresselhaus spin–orbit interactions (SOIs) and the magnetic field effects on off-center hydrogen donor impurity D0 in a two-dimensional Gaussian GaAs quantum dot (QD) are investigated. By performing a unitary transformation, the effect of the SOI incorporated and retained terms up to quadratic in the SOI constants (λR,λD). The variational method is engaged for the ensuing Hamiltonian with improved wave functions to determine the ground, first exited state energies, binding energies, transition energy and susceptibility of a (D0) impurity. The results show that the Rashba spin–orbit interaction (RSOI) reduces, the Dresselhaus spin–orbit interaction (DSOI) and magnetic field enhances the energy of the (D0) impurity. By equating the maximum binding energy of the D0 system with KBT, we calculated the temperatures of the stable D0 impurity. Finally, we calculated the oscillator strength (OS) and compared it to the available literature. OS shows remarkable behaviour to SOIs and QD parameters.

Non-Abelian Berry phase for semiconductor heavy holes under the coexistence of Rashba and Dresselhaus spin-orbit interactions

Non-Abelian Berry phase for semiconductor heavy holes under the coexistence of Rashba and Dresselhaus spin-orbit interactions

A Theoretical Analysis of Spin-Dependent Tunneling in ZnO-Based Heterostructures

The electron tunneling in ZnO/ZnCdO semiconductor heterostructure is studied using the matrix method. The spin-polarization is examined due to Dresselhaus spin–orbit interaction and Rashba spin–orbit interaction. The total spin-polarization is mainly due to Dresselhaus spin–orbit interaction and the Rashba spin–orbit interaction is small. The high degree of spin polarization can be achieved at a high barrier width. With the increasing cadmium concentration in this heterostructure, the spin polarization efficiency is enhanced. The dwell time is reported and discussed.

Spin-texture topology in curved circuits driven by spin-orbit interactions

Interferometry is a powerful technique used to extract valuable information about the wave function of a system. In this work, we study the response of spin carriers to the effective field textures developed in curved one-dimensional interferometric circuits subject to the joint action of Rashba and Dresselhaus spin-orbit interactions. By using a quantum network technique, we establish that the interplay between these two non-Abelian fields and the circuit’s geometry modify the geometrical characteristics of the spinors, particularly on square circuits, leading to the localisation of the electronic wave function and the suppression of the quantum conductance. We propose a topological interpretation by classifying the corresponding spin textures in terms of winding numbers.

Spin-orbit interaction effect on a hydrogenic [formula omitted] centre in a three-dimensional asymmetric Gaussian GaAs quantum dot in a magnetic field

The binding energy of a hydrogenic neutral D0 complex situated in a three-dimensional asymmetric Gaussian GaAs quantum dot is studied incorporating the Rashba and Dresselhaus spin-orbit interactions and the effect of an external magnetic field by means of a variational method and its variation with respect to the quantum dot size, strength of the magnetic field, donor position and spin-orbit coupling strengths is calculated. The behavior of the magnetic susceptibility of the system is also investigated with respect to the magnetic field for different values of the quantum dot parameters.

Effect of vertex corrections on the enhancement of Gilbert damping in spin pumping into a two-dimensional electron gas

We theoretically consider the effect of vertex correction on spin pumping from a ferromagnetic insulator (FI) into a two-dimensional electron gas (2DEG) in which the Rashba and Dresselhaus spin-orbit interactions coexist. The Gilbert damping in the FI is enhanced by elastic spin-flipping or magnon absorption. We show that the Gilbert damping due to elastic spin-flipping is strongly enhanced by the vertex correction when the ratio of the two spin-orbit interactions is near a special value at which the spin relaxation time diverges while that due to magnon absorption shows only small modification. We also show that the shift in the resonant frequency due to elastic spin-flipping is strongly enhanced in a similar way as the Gilbert damping.

Spin-polarised wave-packets transport through one-dimensional nonlinear multiple barriers: Rashba and Dresselhaus Spin–Orbit interactions

ABSTRACT The time evolution of a Gaussian wave packet travelling through a one- dimensional semiconductor based on multiple potential barriers has been explored in order to obtain the spin-based transmission, reflection, and trapping coefficients. We have used a split-step finite difference method to solve the resulting nonlinear coupled Schrodinger equations. The related behaviour of scattering properties of the system as a function of Rashba and Dresselhaus Spin–Orbit interactions, wave-packet velocity, the geometry of the barriers, and the number of neighbouring barriers have been discussed. Based on the results, it is found that by tuning the Rashba and the Dresselhaus coupling strengths, and the characteristics of the system, one can control the spin polarisation of the wave-packet and its propagation coefficients.

Spin-transport across a two-dimensional metal-semiconductor interface with infinite potential in presence of spin-orbit interactions: Double refraction and spin-filtering effect

The spin-transport across a two-dimensional metal-semiconductor junction with a Dirac-delta function potential at the interface and the Rashba and Dresselhaus spin-orbit interactions in the semiconductor region is studied exactly using discontinuous boundary conditions and the spin-polarized reflected and refracted current density and differential conductance are calculated. It is shown that in the presence of an infinite interface potential, an increase in the incident electron's energy reduces the spin splitting. It is also shown that the reflected and refracted coefficients, the spin-polarized currents and the corresponding differential conductance depend strongly on the spin-orbit interactions. The reflected spin polarization, however, becomes zero due to the infinite potential. The Rashba coupling enhances the refracted spin polarization while the Dresselhaus coupling reduces it. Thus, the maximum in polarization occurs at small values of Dresselhaus coupling and large values Rashba coupling. Interestingly, though the presence of delta-potential at the interface does not change the splitting angle between the spin-up and spin-down electrons, it causes a constant shift in the spin polarization.

The diagrammatic method of Berezinskii for one-dimensional disordered wire with spin–orbit interaction

We extend Berezinskii’s diagram technique to the one-dimensional disordered wire containing Rashba and Dresselhaus spin–orbit interactions. The retarded and advanced Green’s functions are factorized in coordinates space in the presence of spin–orbit interactions. This factorization allows us to transform all coordinate dependence of the Green’s functions from lines to the impurity vertices. Our calculations show that all possible impurity vertices giving a contribution to the correlators do not differ from those given in the conventional technique, except that they are written in a 2 × 2 matrix form and the Fermi velocity vF∗ now depends on the spin–orbit coupling constants. The diagrammatic method of Berezinskii with spin–orbit interaction is used to obtain the distribution of the electron density of the localized state p∞(y).

Influence of Magnetic Field on Electron Energy Levels in Semconductor Quantum Dots in the Presence of Spin-Orbit Interactions

Energy levels of electrons in semiconductor quantum dots are obtained within the framework of perturbation theory taking into account the Rashba and Dresselhaus spin-orbit interactions and an external magnetic field. The circular quantum dots are simulated by a new smooth confinement potential of a finite depth and width. The dependence of energy levels on a constant uniform magnetic field and potential parameters is presented.

OPTICAL ABSORPTION IN SEMICONDUCTOR NANOWIRE MEDIATED BY ELECTRON-POLAR OPTICAL PHONON AND SPIN-ORBIT INTERACTIONS

The intrasubband and intersubband absorption of light by free charge carriers in a semiconductor nanowire upon scattering by polar optical phonons mediated by Rashba and Dresselhaus spin-orbit interactions has been studied. The dependence of the absorption coefficient on the energy of the incident photon is investigated by counting the transitions between different conduction subbands. It is shown that the spin-orbit interaction leads to an increase in the coefficient of intrasubband and intersubband absorption of light, with the peaks of the absorption coefficient being determined by the energies of the absorbed photon and the absorbed or emitted phonon. In this case, the difference between the values of the absorption coefficients with or without spin-orbit interaction has maximum in the range of the local minimum of the absorption coefficient obtained by ignoring the spin-orbit coupling.

Spin Textures and Berry Phases for Holes Confined in SiGe Mixed‐Alloy 2D Quantum Well System: Quantization of Berry Phase via Intersubband Interaction

In their last article [Phys. Lett. A 2021, 389, 127091], the authors have extended the approach by considering crossings with the spin–orbit interaction (SOI) up to the second order and studied the spin texture and Berry phase of the heavy‐mass holes (HHs) confined in the SiGe 2D quantum well system. HHs cause quasi‐degeneracy via the intersub‐band interaction (ISI) working as Dirac‐like singularity, leading to the energy‐dependent Berry phase “quantized” by π. This π quantization is understandable by counting the number of quasi‐degenerate points in the Brillouin zone alongside recognizing the sign of the Berry curvature there. Herein, the remaining holes of the light‐mass holes (LHs) and separate holes (SHs) are studied. The spin textures and the Berry curvatures and phases are explored comprehensively, focusing on the competition between the Rashba and Dresselhaus SOIs via ISI. Comparisons with HHs elucidate that LHs and SHs cause similar quasi‐degeneracy through ISI, functioning as the Dirac‐like singularity. As such, the Berry phase is quantized by π, confirming the validity of the counting model irrespective of hole type. In some peculiar cases, HHs and LHs cause a possible sign inversion in the Berry phase, leading to zero Berry phase against temperature.

Spin-Hall conductivity and Hall angle in a two-dimensional system with impurities in the presence of spin–orbit interactions

We investigate the spin-torque-dependent Spin Hall phenomenon in a two-dimensional tight-binding system in the presence of Rashba and Dresselhaus spin–orbit interactions and random static impurities. We employ the Matsubara Green function techniques to calculate the relaxation time caused by the scattering of electrons by impurities. The longitudinal and transverse conductivities are next calculated with the help of the Kubo formalism. We have also calculated the spin Hall angle for the present model and studied its dependence on spin–orbit interactions and impurity strength. Finally, we explore the effect of interplay between the Rashba and Dresselhaus interactions on the spin-Hall effect.

Spin splitting of the conduction band by exchange interaction in the valence band through a k·p interband process in ferromagnetic semiconductors

The momentum-dependent spin splitting in the conduction band couples orbital motion to spin and enables electrical control of spin. Currently, this control relies on the relativistic spin-orbit interaction (SOI), which limits useful materials to those containing heavy elements. Recently, Naka et al. [Nat. Commun. 10, 4305 (2019)] have found a momentum-dependent spin splitting originating from the exchange interaction, which is expected to extend spintronic materials to those without heavy elements. In this paper, we propose a mechanism of the exchange-induced orbital-spin coupling by extending the $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ theory. As an example, we consider an $n$-type ferromagnetic semiconductor (nFMS) of ${T}_{d}$ point group symmetry with the $p\text{\ensuremath{-}}d$ exchange interaction between an electron in the valence band and the spin of a magnetic ion and evaluate the spin splitting in the conduction band of ${\mathrm{\ensuremath{\Gamma}}}_{6}$ irreducible representation from the eight-band $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ Hamiltonian. We find that the lowest-order spin splitting in bulk is of the second order of momentum, which results in a nonzero splitting at ${k}_{x}={k}_{y}=0$ in a quantum well with a nonzero quantized momentum ${k}_{z}$. An estimation shows that the $p\text{\ensuremath{-}}d$ exchange interaction is the dominant origin of the conduction-band spin splitting in InFeAs nFMS. We also calculate the intrinsic anomalous Hall conductivity of bulk InFeAs generated by the $p\text{\ensuremath{-}}d$ exchange, which provides both the coupling of orbital motion to spin and that of spin to nFMS magnetization. We find that the $p\text{\ensuremath{-}}d$ exchange-induced Hall conductivity exhibits an accelerated increase with Fe density, in contrast to that produced by the $s\text{\ensuremath{-}}d$ exchange and the Dresselhaus SOI. This finding suggests that the extended $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ mechanism of orbital-spin coupling is expected to help find remarkable phenomena and useful applications in a wide variety of materials and structures.

Simultaneous effects of the confinement of polar optical phonons and spin-orbit coupling on the free carrier absorption of a nanowire

The free carrier absorption of light in a quantum wire is studied for the case when electrons are scattered by polar optical phonons, taking into account both the phonon confinement and the Rashba and Dresselhaus spin-orbit interactions. The dependencies of the absorption coefficient on the energies of the incident photons and the confining potential as well as on the temperature and electric field strength are investigated. We confirm that the spin-orbit interaction leads to an overall increase in the light absorption coefficient. It is shown that for the intrasubband electronic transitions the peaks of the absorption coefficient are obtained when the photon energy coincides with the energy of the LO phonon. Moreover, the spin-orbit interaction leads to a blue-shift of the absorption peak.

Identification of a state of persistent spin helix in a parallel magnetic field, and exploration of its transport properties

The tensors of conductivity and spin susceptibility of a two-dimensional electron gas (2DEG) with equal Rashba and Dresselhaus spin-orbit interaction constants [the persistent spin helix (PSH) state] in a parallel magnetic field are calculated. Applying a parallel magnetic field to the PSH state leads to the appearance of a saddle point in the spectrum and, accordingly, to a Van Hove singularity (VHS), whose amplitude increases indefinitely as the magnetic field strength $(\mathbf{b})$ approaches to some critical value ${b}_{cr}$. The presence of a VHS in the density of states is an important factor determining the conductivity and spin susceptibility tensors. When only the lower spin subband is filled, the off-diagonal elements of the conductivity tensor are nonzero; that is, a Hall voltage arises due to the anisotropy of the Fermi surface and scattering. In the region where two spin subbands are filled, the diagonal and off-diagonal components of the spin susceptibility tensor are equal, and the off-diagonal terms of the conductivity tensor vanish. A sharp decrease in the conductivity and spin susceptibility at the beginning of the filling of the second spin subband, the ratio of the diagonal component of the spin susceptibility to the off-diagonal one, and also the number of critical points in the spectrum make it possible to establish the PSH 2DEG state.

Dynamics of the angular momentum in narrow quantum rings with Rashba and Dresselhaus spin-orbit interactions

The quantum dynamics of the electron's spin and orbital angular momenta in semiconductor quantum rings is analyzed. Both Rashba and Dresselhaus spin-orbit interactions (SOIs) in their quasi-two-dimensional forms are taken into account. The narrow quantum rings are treated with models including one and two radial modes. We find that when either Rashba or Dresselhaus SOI acts alone, the different angular momentum states are coupled in blocks of two (for a single radial mode) or four (for two radial modes). We also show that the full Hilbert space splits into two disjoint subspaces, which are not coupled by either of the two SOIs, thereby decoupling accordingly the state evolution. When both SOI mechanisms are present, in principle infinitely many states are coupled, but we find by numerical computation of the quantum dynamics that for typical evolution times in practice only a few neighboring states are involved in the dynamics. Thus the exchange of angular momenta proceeds only via very few states. Furthermore, we find a trend that when initially high orbital momenta are prepared, the time evolution of spin and orbital momenta is almost unaffected by the availability of a second radial mode, in sharp contrast to the case of preparing the system in low orbital angular momentum states. The implications of our findings for the coherent control of angular momentum in quantum rings are pointed out.