Dresselhaus Interaction Research Articles

Hexagonal MnTe with Antiferromagnetic Spin Splitting and Hidden Rashba–Dresselhaus Interaction for Antiferromagnetic Spintronics

AbstractHexagonal MnTe emerges as a critical component in designing magnetic quantum heterostructures, calling for a detailed study. After finding a suitable combination of exchange–correlation functional and corrections, this study within ab initio density functional theory uncovers an insulating state with a preferred antiferromagnetic (AFM) order. The exchange interaction strengths are computed to estimate the AFM ordering temperature via Monte Carlo calculations. These calculations and symmetry analysis reveal a large spin splitting in the system due to the AFM order without considering spin–orbit interaction, except in the kx‐ky plane. Critically examining the band dispersion and spin textures obtained from these calculations and comparing them with an insightful symmetry analysis and analytical model, a combined Rashba–Dresselhaus interaction in the kx‐ky plane, around the K point of the system, is confirmed. These results and insights would help design heterostructures of MnTe for technological applications.

Impact of the p-cubic Dresselhaus term on the spin Hall effect

It is well known that the Dresselhaus spin-orbit coupling (SOC) in semiconductor two dimensional electron gases (2DEGs) possesses both linear and cubic in momentum contributions. Nevertheless, the latter is usually neglected in most theoretical studies. However, recent Kerr rotation experiments have revealed a significant enhancement of the cubic Dresselhaus interaction by increasing the drift velocities in 2DEGs hosted in GaAs quantum wells. Here, we present a study of the optical spin Hall conductivity in 2DEGs under the simultaneous presence of Rashba and (linear plus cubic) Dresselhaus SOC. The work was done within the Kubo formalism in linear response. We show that the coexistence of the Rashba and cubic Dresselhaus SOC in 2DEGs promotes a strong anisotropy of the band spin splitting which in turn leads to a very characteristic frequency dependence of the spin Hall conductivity. We find that the spin Hall conductivity response could be very sensible to sizeable cubic-Dresselhaus coupling strength. This may be of relevance for the optical control of spin currents in 2DEGs with non-negligible cubic-Dresselhaus SOC.

Spin-orbit interaction effects on a [formula omitted] complex in a GaAs quantum dot in a magnetic field

The spin-orbit interaction effects on the energetics of a negative donor centre localized in a 3D Gaussian GaAs quantum dot placed in a magnetic field are studied variationally by using a unitary transformation and a Jastrow function to incorporate the role of Coulomb interaction. The Dresselhaus interaction is shown to increase the binding of the negative donor. The diamagnetic susceptibility and the dipole moment of the system are also calculated.

Formation of the skyrmionic polaron by Rashba and Dresselhaus spin-orbit coupling

Skyrmions in reduced dimensions such as thin layers and interfaces are of both fundamental and technological importance. In these systems, itinerant electrons are often present together with the Rashba and Dresselhaus spin-orbit coupling (SOC). Here, we show that an itinerant electron in the presence of these interactions can nucleate the skyrmion state, even when the standard Dzyaloshinskii-Moriya interaction (DMI) is absent, and the electron can become self-trapped in the skyrmion core, forming the ``skyrmionic polaron'' (SkP). The formation of the SkP is investigated from a continuum model of the electron, exchange coupled to the lattice spins, by solving the appropriate Euler-Lagrange equations. The skyrmion (antiskyrmion) texture is favored by the Rashba (Dresselhaus) SOC, with the binding energy increasing quadratically with the strength of the interaction. In contrast, if the skyrmion is already formed due to a nonzero DMI, the electron is delocalized and avoids the skyrmion core until the strength of the Rashba or Dresselhaus SOC exceeds a critical value. Below this critical value, the electron is not bound to the skyrmion core, the polaron does not form, and the electron has little effect on the skyrmion state. Our work envisions the possibility of manipulating the skyrmion state in device applications by altering the strength of the Rashba or Dresselhaus interactions, e.g., by an external electric field.

Spin quantum transport in double top-gate system

The quantum transport in an n-type two-dimensional electron gas (2DEG) with a double top gate system is investigated. A propagation matrix method is used to derive the band structure and obtain the conductance of the considered system. The results show that in the presence of the Rashba and the Zeeman interactions, resonance peaks and hole-like bound state structure are formed in the conductance spectra influenced by the gate potential and gate distance. While, under the influence of the Rashba–Dresselhaus and the Zeeman interactions, resonance peaks and inner-mode resonance conductance peaks are formed reflecting the gate potential and the gate distance. Notably, when the Dresselhaus interaction reaches a certain strength, the partial conductance of the spin-preservation internal mode becomes significant. Finally, a simple transcendental equation is found to estimate the energy of a bound state.

Rashba-like spin-orbit interaction and spin texture at the KTaO3(001) surface from DFT calculations

Rashba-like spin-orbit interaction at oxide heterostructures emerges as a much sought-after feature in the context of oxide spintronics and spin-orbitronics. ${\mathrm{KTaO}}_{3}$ (KTO) is one of the best substrates available for the purpose, owing to its strong spin-orbit interaction and alternating $+1|\ensuremath{-}1$ charged layers along the (001) direction. Employing first-principles calculations within density functional theory (DFT) and proposing a possible electrostatic model for charge transfer to the surfaces of KTO slabs, we comprehensively analyze Rashba-like spin-orbit interaction with the help of three-dimensional (3D) band dispersion, isoenergetic contours, and projected spin textures -- all directly obtained from our DFT calculations -- in a thin insulating slab and a conducting thick slab of KTO. Our results reveal reasonably strong linear Rashba interaction with no signature of Dresselhaus or higher order Rashba interactions in the systems considered here. The rigorous analysis presented here may be crucial for future developments in oxide spintronics.

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 Hall effect in two-dimensional InSe: Interplay between Rashba and Dresselhaus spin-orbit couplings

Materials with inversion asymmetries can exhibit strong spin Hall effect (SHE) in the presence of Dresselhaus and Rashba spin-orbit coupling (D/R SOC) interactions. Ideally, in a two-dimensional crystal, inversion asymmetry could be modulated by stacking order and external perturbations. Here, using first-principles calculations, we systematically investigate the interplay between DSOC and RSOC and their influences on SHE in mono- and bilayer InSe. We show that in the presence of DSOC, the introduction of Rashba interaction through gate voltages in monolayer InSe increases Zeeman-like spin splitting around the Brillouin-zone center and contributes to the enhancement of spin Hall conductivity (SHC), which reaches a saturation point due to the RSOC-enforced spiral-spin texture. The SHC in the unperturbed centrosymmetric $\mathit{AB}$ stacked bilayer shows a peak associated with the Mexican-hat-like valence-band edge; however, in a wide energy range the SHC stays insignificant. In the $\mathit{AB}$\ensuremath{'} stacked bilayer with the intrinsic RSOC present, the value of SHC can be comparable to that of $\mathit{AB}$ stacked bilayer with an external electric field. Moreover, we show that the spin-momentum locking in the $\mathit{AB}$\ensuremath{'} stacked bilayer is switchable by a gate voltage. These findings provide a promising route for spintronic and magneto-optical applications by exploiting the rich physics of spin-orbit effects.

Non-equilibrium spin polarization in magnetic two-dimensional electron gas with k-linear and k-cubed Dresselhaus spin–orbit interaction

The current-induced spin polarization (CISP) of charge carriers is one of the main mechanisms of spin-to-charge interconversion effects that can be used in new spintronics devices. Here, CISP is studied theoretically in symmetric quantum wells growing in [001] crystallographic direction, where both k -linear and k -cubed Dresselhaus spin–orbit interactions are present. The exchange interaction responsible for perpendicular to plane net magnetization is also taken into account. The main focus is on the influence of cubic Dresselhaus term on CISP and the interplay between spin–orbit interaction (SOI) and the exchange field. The analytical and numerical results are derived within the linear response theory and Matsubara Green’s function formalism. Apart from detailed numerical results, we also provide some analytical expressions that may be useful for interpretation of experimental results and for characterization of quantum wells with Dresselhaus SOI. Analytical expressions for the relevant Berry curvature are also derived, and it is shown that the Berry curvature in magnetic 2DEG with cubic Dresselhaus interaction oscillates in the k -space, while its averaged value is reduced. We also analyze the temperature behavior of CISP and calculate the low-temperature spin polarizability due to heat current. • The effects of the interplay of Dresselhaus spin–orbit interaction (SOI) (with both k -linear and k -cubed terms) and exchange interaction on the nonequilibrium current-induced spin polarization, have been analyzed. • The k -cubed term in Dresselhaus SOI leads to a decrease in nonequilibrium spin density with increasing chemical potential. • The cubic Dresselhaus SOI in magnetic 2DEG creates Berry curvature oscillations in the k -space and reduces the Berry curvature with increasing energy. • The out of plane magnetization leads to an additional component of spin polarization and also to anomalous Hall conductivity that is robust against impurities. • Thermally-induced spin-polarization is analyzed and is shown to be remarkable in a well-defined range of chemical potential.

Double refraction of electron spin across a metal-semiconductor junction with Rashba and Dresselhaus spin-orbit interactions: A stronger spin-filtering effect

The reflection and refraction of electrons across a two-dimensional metal-semiconductor tunnel junction are studied incorporating both Rashba and Dresselhaus spin-orbit interactions for the semiconductor region. The effects of incident electron energy , angle of incidence and spin-orbit interactions on the angles of refraction of the spin-up and spin-down electrons are calculated exactly. It is shown that the Dresselhaus interaction decreases the angle of refraction for the spin-down electrons more than the spin-up electrons causing a larger splitting between the spin-up and spin-down electrons. Also an increase in the incident energy is shown to increase the spin-filtering effect. The refraction coefficients, spin-up and spin-down current densities and tunnelling conductance are also studied with respect to spin-orbit interactions. Finally, the spin polarization current is determined in the semiconductor region in the presence of Rashba interaction alone and in the presence of both Rashba and Dresselhaus interactions. • Tunneling of electrons across a 2D metal-semiconductor junction is considered. • Rashba and Dresselhaus interactions are incorporated only for semiconductor region. • Reflection and refraction of spin-up and spin-down electrons are calculated exactly. • Dresselhaus interaction enhances the splitting between up- and down-spin electrons. • Spin polarization current is also determined in semiconductor region.

Electron density effect on spin-orbit interaction in [001] GaAs quantum wells

The spin-orbit interaction of two-dimensional (2D) electrons in semiconductor quantum wells gives rise to a variety of interesting transport and optical spin-dependent effects. In the GaAs/AlGaAs type heterosystems, this interaction consists of the isotropic Bychkov-Rashba term, which is absent in symmetric wells, and the anisotropic Dresselhaus term, reflecting the lattice symmetry. It is well-known that the first term can be controlled by electric fields in the growth direction: external or internal, induced by a charge density of 2D electrons. In this work we reveal that the 2D electron charge can substantially affect also the Dresselhaus interaction in symmetric quantum wells. Within the one-band electron Hamiltonian containing, together with the bulk Dresselhaus interaction, the two contributions to the Dresselhaus term from the quantum well interfaces, we show that the internal electric field from the 2D electron charge density can substantially renormalize the anisotropic spin-orbit interaction of 2D electrons. This effect may be important in quantitative studies of spin-dependent phenomena in quantum wells.

Minimal length, Berry phase and spin-orbit interactions

Bearing the perturbation method in mind, and by focusing on the first order of approximation, the effect of Generalized Uncertainty Principle (GUP) on the Berry phase is investigated. Thereinafter, we apply the obtained formulation to quantum ring including two sorts of spin-orbit interactions, namely Rashba and Dresselhaus interactions, which are accessible for electrons. Finally, a comparison between the results and the accuracy of Berry phase detectors helps us in finding out β 0 < 1046 and β 0 < 1051 as the upper bounds on the GUP parameter inflicted by the Rashba and Dresselhaus interactions, respectively.

Spin transport in a two-dimensional tight-binding system with Rashba and Dresselhaus spin-orbit interactions in the presence of static random disorder

The longitudinal charge and spin conductivities for a two-dimensional system with random static disorder are investigated in the presence of Rashba and Dresselhaus spin-orbit interactions. The Matsubara Green function technique is used to determine the relaxation time for the impurity scattering and the charge and spin conductivities are obtained by employing the Kubo formalism. It is shown that the spin and charge conductivities are enhanced by the Rashba and Dresselhaus spin-orbit interactions while they are reduced by the presence of impurities. Finally, the effects of Rashba and Dresselhaus interactions on the ratio of longitudinal spin conductivity to charge conductivity are studied.

Magnetic Field and Hydrostatic Pressure Effects on Electron Transport in Heterostructure Based on InAs/GaAs Triple Barriers with Dresselhaus Interaction

This paper theoretically examines the spin-dependent transport of electrons through InAs/GaAs symmetric triple barriers by solving the spin-dependent Schrodinger equation. The Transfer Matrix Method (TMM) was used to investigate the impact of the hydrostatic pressure, temperature, and magnetic field on the transmission coefficient and spin polarization of electrons while taking into account the Rashba and Dresselhaus spin orbit interactions. The results indicate that when both the hydrostatic pressure and temperature increase, the two resonant states of spin-up and down electrons move toward lower energies (blue shift). In addition, when the magnitude of the applied magnetic field increases, the resonant states of spin-up electrons shift toward lower energies, whereas the spin-down ones shift toward higher energies, which leads to perfect spin separation. This important spin-separation behavior could be very useful in the design of spin filters, which are strongly required in spintronics applications.

Narrow quantum rings with general Rashba and Dresselhaus spin-orbit interactions

We solve analytically the energy eigenvalue problem of narrow semiconductor quantum rings with a general spin-orbit term that includes as a special case the Rashba and Dresselhaus interactions acting simultaneously. The eigenstates and eigenenergies of the system are found for arbitrary values of the spin-orbit coupling constants without making use of approximations. The general eigenstates are expressed as products of a scalar Mathieu function and a spinor factor which is periodic or pseudo-periodic on the ring. Our general solution reduces to the previously found solutions for particular combinations of the Rashba and Dresselhaus couplings, like the well-studied cases of Rashba-only and of equal coupling constants.

Role of spin-orbit interactions on the entropy and heat capacity of a quantum dot helium placed in an external magnetic field

The effects of Rashba, Dresselhaus and Coulomb interactions on the entropy and heat capacity of a two-electron quantum dot placed in an external magnetic field are studied at finite temperature. The effect of electron-electron interaction is studied by using the Johnson-Payne harmonic model which is exactly soluble, while the Rashba and Dresselhus spin-orbit coupling effects are dealt with using unitary transformations. It is observed that as a function of the magnetic field, the heat capacity has a double peak structure with the minima between the peaks occurring at the singlet-triplet transition point and the e-e interaction shifts the peaks to lower magnetic fields. It is also observed that the coulomb correlation reduces the heat capacity in the low temperature regime while in the high temperature regime it enhances it. Interestingly, however, in the high field regime, the heat capacity does not seem to be influenced by the electron-electron interaction. The entropy is found to show a single peak as a function of magnetic field at the singlet-triplet transition point. The Rashba spin-orbit interaction reduces the heat capacity and the Dresselhaus interaction enhances it whereas the opposite effect is exhibited by the entropy. The temperature behaviour of both the entropy and heat capacity clearly demonstrates the effect of zero field spin-splitting. • A quantum dot with two electrons is considered in a magnetic field at finite temperature. • Role of Rashba and Dresselhauss interactions (RI & DI) are studied on heat capacity ( C v ) and entropy (S). • Coulomb interaction between electrons is treated by the exactly soluble Johnson-Payne model. • RI reduces C v and DI enhances it while S shows just an opposite behaviour. • Temperature behaviour of C v and S exhibits zero-field splitting.

Symmetry breaking of the persistent spin helix in quantum transport

We exploit the high-symmetry spin state obtained for equal Rashba and linear Dresselhaus interactions to derive a closed-form expression for the weak localization magnetoconductivity -- the paradigmatic signature of spin-orbit coupling in quantum transport. The small parameter of the theory is the deviation from the symmetry state introduced by the mismatch of the linear terms and by the cubic Dresselhaus term. In this regime, we perform quantum transport experiments in GaAs quantum wells. Top and back gates allow independent tuning of the Rashba and Dresselhaus terms in order to explore the broken-symmetry regime where the formula applies. We present a reliable two-step method to extract all parameters from fits to the new expression, obtaining excellent agreement with recent experiments. This provides experimental confirmation of the new theory, and advances spin-orbit coupling towards a powerful resource in emerging quantum technologies.

Combined Resonance of the Interlayer Conductivity in Quasi-Two-Dimensional Conductors

Analytical expressions have been obtained for the resonance component of the interlayer conductivity of quasi-two-dimensional conductors in an inclined magnetic field in the presence of the Rashba—Dresselhaus spin-orbit coupling. It has been shown that the Dresselhaus interaction makes the main contribution to resonances at combination frequencies in the range of angles between the magnetic field and normal to the conducting layers where angular oscillations of the conductivity occur. The results can be used to experimentally determine the absolute values of the spin-orbit coupling constants.

Quantum Adiabatic Pumping in Rashba- Dresselhaus-Aharonov-Bohm Interferometer

We investigate the quantum adiabatic pumping effect in an interferometer attached to two one-dimensional leads. The interferometer is subjected to an Aharonov-Bohm flux and Rashba-Dresselhaus spin-orbit interaction. Using Brouwer’s formula and rigorous scattering eigenstates, we obtained the general closed formula for the pumping Berry curvatures depending on spin for general interferometers when the external control parameters only modulate the scattering eigenstates and corresponding eigenvalues. In this situation, pumping effect is absent in the combination of the control parameters of Aharonov-Bohm flux and spin-orbit interaction strength. We have shown that finite pumping is possible by modulating both Rashba and Dresselhaus interaction strengths and explicitly demonstrated the spin-pumping effect in a diamond-shaped interferometer made of four sites.

Spin interferometry in anisotropic spin-orbit fields

Electron spins in a two-dimensional electron gas (2DEG) can be manipulated by spin-orbit (SO) fields originating from either Rashba or Dresselhaus interactions with independent isotropic characteristics. Together, though, they produce anisotropic SO fields with consequences on quantum transport through spin interference. Here we study the transport properties of modelled mesoscopic rings subject to Rashba and Dresselhaus [001] SO couplings in the presence of an additional in-plane Zeeman field acting as a probe. By means of 1D and 2D quantum transport simulations we show that this setting presents anisotropies in the quantum resistance as a function of the Zeeman field direction. Moreover, the anisotropic resistance can be tuned by the Rashba strength up to the point to invert its response to the Zeeman field. We also find that a topological transition in the field texture that is associated with a geometric phase switching is imprinted in the anisotropy pattern. We conclude that resistance anisotropy measurements can reveal signatures of SO textures and geometric phases in spin carriers.