Rashba Spin-orbit Interaction Research Articles

Antiparallel Spin Polarization and Spin Current Induced by Thermal Current and Locally Broken Inversion Symmetry in a Double‐Quantum Well Structure

Generating a nonequilibrium spin polarization with a driving force is first realized by the electric current in a system with broken inversion symmetry and extended to that induced by the thermal current and that appearing in an inversion‐symmetric system with locally broken inversion symmetry. This article theoretically explores the spin polarization generated by the thermal current and the locally broken inversion symmetry in a symmetric double‐quantum well structure (DQWS). This thermally induced spin polarization (TISP) appears in the antiparallel configuration with the TISP of two wells in opposite directions. The calculation using the Boltzmann equation in the relaxation‐time approximation under the condition of zero charge current shows that the local TISP exhibits the maximum at a finite Rashba spin–orbit interaction when the electron density is fixed. This is because the local TISP in the DQWS is enhanced at the chemical potential near the bottom of the first‐excited sub‐band. This enhancement also occurs in a single quantum well with globally broken inversion symmetry. Another finding is that the maximum of the local TISP appears at a nonzero interwell coupling. The spin current by the diffusion of the local TISP into an adjacent electrode is also calculated.

Nonlinear transport and radio frequency rectification in BiTeBr at room temperature

Materials showing second-order nonlinear transport under time reversal symmetry can be used for Radio Frequency (RF) rectification, but practical application demands room temperature operation and sensitivity to microwatts level RF signals in the ambient. In this study, we demonstrate that BiTeBr exhibits a giant nonlinear response which persists up to 350 K. Through scaling and symmetry analysis, we show that skew scattering is the dominant mechanism. Additionally, the sign of the nonlinear response can be electrically switched by tuning the Fermi energy. Theoretical analysis suggests that the large Rashba spin-orbit interactions (SOI), which gives rise to the chirality of the Bloch electrons, provide the microscopic origin of the observed nonlinear response. Our BiTeBr rectifier is capable of rectifying radiation within the frequency range of 0.2 to 6 gigahertz at room temperature, even at extremely low power levels of −15 dBm, and without the need for external biasing. Our work highlights that materials exhibiting large Rashba SOI have the potential to exhibit nonlinear responses at room temperature, making them promising candidates for harvesting high-frequency and low-power ambient electromagnetic energy.

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.

Correction: Theoretical studies on the effects of pressure, temperature, and aluminum concentration on the optical absorption, refractive index and group velocity within GaAs/Ga1–xAlxAs quantum ring in the presence of Rashba spin–orbit interaction

Correction: Theoretical studies on the effects of pressure, temperature, and aluminum concentration on the optical absorption, refractive index and group velocity within GaAs/Ga1–xAlxAs quantum ring in the presence of Rashba spin–orbit interaction

Bilinear magnetoresistance in 2DEG with isotropic cubic Rashba spin–orbit interaction

Bilinear magnetoresistance has been studied theoretically in 2D systems with isotropic cubic form of Rashba spin–orbit interaction. We have derived the effective spin–orbital field due to current-induced spin polarization and discussed its contribution to the unidirectional system response. The analyzed model can be applied to the semiconductor quantum wells as well as 2DEG at the surfaces and interfaces of perovskite oxides.

Tuning the spin transport properties of phosphorene superlattice under a uniform electric field and Rashba spin-orbit interaction

The spin-interdependent transport features for phosphorene superlattice, containing spin-flip and spin polarization are described under a constant electric field and extrinsic Rashba spin-orbit interaction utilizing the transfer matrix method. Our findings demonstrated the number of barriers at this structure acts the prominent role at the spin polarization and transmission probability, that can be applied in modeling optimum spintronic apparatus. Interestingly, the best outcomes for the transmission probability and spin polarization transpired in the five obstacles. Furthermore, an incoming electron with spin-up (down) can be transferred as an electron with spin-down (up) by adjusting the bias voltage and Rashba strength. Our findings can be utilized to create new nanostructures and maximize the performance of spintronic systems based on phosphorene nanoribbons.

Effect of intrinsic & Rashba spin-orbit interactions (SOI) in case of bilayer graphene

In this study, we investigated how various SOI affect the properties of bilayer graphene’s energy band structure. We have considered intralayer interactions in this work. We focused on the system without biasing. We found that the intrinsic spin-orbit interaction (ISOI) can produce an energy band gap in bilayer graphene. On the other hand, in the case of an intralayer Rashba spin-orbit interaction (RSOI) different energy bands exist. The results shown depicts how the behaviour of the energy bands remains the same when we are increasing the number of atoms (N) in a unit cell of bilayer graphene.

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.

Theoretical studies on the effects of pressure, temperature, and aluminum concentration on the optical absorption, refractive index and group velocity within GaAs/Ga1−xAlxAs quantum ring in the presence of Rashba spin–orbit interaction

Theoretical studies on the effects of pressure, temperature, and aluminum concentration on the optical absorption, refractive index and group velocity within GaAs/Ga1−xAlxAs quantum ring in the presence of Rashba spin–orbit interaction

Effects of electron–phonon coupling and Rashba spin–orbit interaction on thermodynamic and magnetic properties of quantum dots

The thermodynamic and magnetic properties of quantum-dot structures subjected to an applied magnetic field were studied, including the longitudinal optical–phonon interaction and the Rashba spin–orbit effect. The Schrödinger equation was solved to determine the energy levels. The partition function was evaluated by summing the accessible energy levels and was then utilized to calculate the thermomagnetic functions. In this paper, we present magnetic properties by considering three interacting polarons. Our results indicated that at B=0T, the susceptibility exhibits diamagnetic behavior for all values of the Rashba spin–orbit parameter. However, the magnetic susceptibility increases with an applied magnetic field, and the system exhibits paramagnetic behavior under moderate magnetic fields. However, in situations with and without the polaron effect, the susceptibility is saturated at 0(meV/T2) under large magnetic fields. In this study, we showed that the Rashba spin–orbit interaction (SOI) strengthens the cutoff magnetic field Bc (the B value at which the magnetic nature of the dot changes from diamagnetic to paramagnetic). Rashba SOIs reduce the mean energy of the system, including polaronic interactions. Under the polaron effect, the heat capacity curve shifts to lower temperatures. A quantitative description of the magnetocaloric effect (ΔS) as a function of the Wigner and Rashba spin–orbit parameters is presented.

Possible zero-magnetic field fractional quantization in In0.75Ga0.25As heterostructures

In this Letter, we report a systematic study of a structure found in zero magnetic field at or near 0.2 ×(e2/h) in In0.75Ga0.25As heterostructures, where e is the fundamental unit of charge and h is Planck's constant. This structure has been observed in many samples and stays at near constant conductance despite a large range of external potential changes, the stability indicating a quantum state. We have also studied the structure in the presence of high in-plane magnetic fields and find an anisotropy which can be related to the Rashba spin–orbit interaction and agrees with a recent theory based on the formation of coherent back-scattering. A possible state with conductance at 0.25 ×(e2/h) has also been found. The quantum states described here will help with the fundamental understanding of low-dimensional electronic systems with strong spin–orbit coupling and may offer new perspectives for future applications in quantum information schemes.

Thermodynamic Properties of Conical Quantum Dot Modulated by External Fields and Rashba Spin–Orbit Interaction

Thermodynamic Properties of Conical Quantum Dot Modulated by External Fields and Rashba Spin–Orbit Interaction

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

Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions.

We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field and report on phase shifts in the current-phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to φ0 = 0.5π, which are consistent with a Zeeman field coupling to highly transmissive Andreev bound states via Rashba spin-orbit interaction. A distinct phase shift emerges at larger fields, concomitant with a switching current minimum and the closing and reopening of the superconducting gap. These signatures of an induced phase transition, which might resemble a topological transition, scale with the superconducting lead size, demonstrating the crucial role of orbital effects. Our results elucidate the interplay of Zeeman, spin-orbit, and orbital effects in InAs/Al JJs, giving improved understanding of phase transitions in hybrid JJs and their applications in quantum computing and superconducting electronics.

Hole-Spin Driving by Strain-Induced Spin-Orbit Interactions.

Hole spins in semiconductor quantum dots can be efficiently manipulated with radio-frequency electric fields owing to the strong spin-orbit interactions in the valence bands. Here we show that the motion of the dot in inhomogeneous strain fields gives rise to linear Rashba spin-orbit interactions (with spatially dependent spin-orbit lengths) and g-factor modulations that allow for fast Rabi oscillations. Such inhomogeneous strains build up spontaneously in the devices due to process and cool down stress. We discuss spin qubits in Ge/GeSi heterostructures as an illustration. We highlight that Rabi frequencies can be enhanced by 1 order of magnitude by shear strain gradients as small as 3×10^{-6} nm^{-1} within the dots. This underlines that spins in solids can be very sensitive to strains and opens the way for strain engineering in hole spin devices for quantum information and spintronics.

Spin filtration in generalized Sierpinski triangles in presence of Rashba spin–orbit interaction

In this work, we theoretically investigate the phenomenon of spin polarization in generalized Sierpinski gasket (SPG) triangles (, , , ) in the presence of Rashba spin–orbit interaction (RSOI) within a tight-binding framework. The geometrical construction is addressed for all four types of generalized SPG triangles using an iterative function system that begins with a fixed triangle of any arbitrary side length. The geometry of various types of fractal networks has a major impact on the degeneracy of the energy spectrum. It is shown that only the two-terminal setup in the presence of RSOI is incapable of breaking the spin degeneracy, which necessitates the use of a three-terminal setup to break the time-reversal symmetry. The effect of flip map induced anisotropic hopping integrals on three-terminal spin-resolved transmission probabilities is studied. In several cases, we find almost spin polarization in our considered lattices. We also analyze how spin polarization varies with RSOI strength and fractal generations. Our results indicate that fractal lattices might be suitable functional elements for designing future spin-based electronic devices.

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.

Flux-periodic oscillations in proximitized core–shell nanowires

Flux-periodic oscillations of the superconducting gap in proximitized core–shell nanowires are explored. Periodicity of oscillations in the energy spectrum of a cylindrical nanowire is compared with nanowires having hexagonal and square cross-section geometry, along with the effects of Zeeman and Rashba spin–orbit interaction. A transition between h/e and h/2e periodicity is found and shown to be dependent on the chemical potential, with correspondence to degeneracy points of the angular momentum quantum number. For a thin shell of a square nanowire, solely h/e periodicity is found in the infinite wire spectrum and shown to result from energy separation between the lowest groups of excited states.

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.