Dresselhaus Spin Orbit Research Articles

A Giant Bulk‐Type Dresselhaus Splitting with 3D Chiral Spin Texture in IrBiSe

Materials with giant spin splitting are desired for spintronic applications. The fabrications of spintronic devices from half metals with one spin direction are often hampered, however, by stray magnetic fields, domain walls, short spin coherence times, scattering on magnetic atoms or magnetically active interfaces, and other characteristics that come along with the magnetism. The surfaces of topological insulators, or Dirac/Weyl semimetals, could be an alternative, but production of high‐quality thin films without the presence of the bulk states at the Fermi energy remains very challenging. Here, by utilizing angle‐resolved photoemission spectroscopy, a record‐high Dresselhaus spin–orbit splitting of the bulk state in the nonmagnetic IrBiSe is found. The band structure calculations indicate that the splitting band is fully spin‐polarized with 3D chiral spin texture. As a source of spin‐polarized electrons, lightly doped IrBiSe is expected to generate electric‐field‐controlled spin‐polarized currents, free from back scattering, and could host triplet and Fulde–Ferrel–Larkin–Ovchinnikov (FFLO) superconductivity.

Influence of spin–orbit interaction, Zeeman effect and light polarisation on the electronic and optical properties of pseudo-elliptic quantum rings under magnetic field

ABSTRACTWe theoretically investigated the influences of the magnetic field and light polarisation on the electronic and optical properties of a GaAs/GaAlAs pseudo-elliptic quantum ring, modelled by an outer ellipsis and an inner circle, in the presence of the Rashba and Dresselhaus spin–orbit interactions and Zeeman effect. We show that Aharonov-Bohm oscillations of the energy spectrum are not affected by the presence of the Zeeman effect alone but, in the presence of Rashba and Dresselhaus spin–orbit couplings, the periodicity of certain levels becomes hardly definite. The Zeeman effect generally enhances/diminishes the separation levels produced by Rashba/Dresselhaus interactions (SOI) and when both types of SOI are considered, the effect depends on their relative strength. The magnetic field can trigger spin-flip for each type of spin–orbit interaction and Zeeman effect or their combination through anticrossings in the energy spectra. Our results reveal that the absorption spectra are very sensitive to the magnetic field and light polarisation. For all polarisations considered, the magnetic field increment leads to the redshift or blueshift of some particular peaks (an effect of this ring geometry) and a better separation of the peaks. The x-polarised light determines spectra with many small, but separated peaks while the circular polarised light leads to spectra with large peaks of high amplitude.

Transient diffusive spin dynamics in intrinsic InGaAs/InAlAs multiple quantum wells

Spatial and temporal diffusive spin dynamics in the transient regime for 10-nm-wide InGaAs/InAlAs quantum wells were investigated using time-resolved optical Kerr rotation (TRKR) microscopy. The transient regime of diffusive spin dynamics is a specific regime which appears after local excitation but before the formation of a spin mode. In this regime, the spin precession frequency induced by the spin–orbit (SO) magnetic field decreases with time since the diffusive velocity decreases as the distribution of spins expands. In this study, by decreasing the spot size of the excitation pulse, we examined the spin dynamics in the transient regime. We carefully analyzed the TRKR signals using time-dependent frequency equations established by Kohda et al. [Appl. Phys. Lett. 107, 172402 (2015)]. All the TRKR signals could be well reproduced by the time-dependent frequency equations. Our analysis reveals that the spin precession frequencies arising from the SO interaction gradually decrease with time, and they allowed the extraction of the Rashba and Dresselhaus SO parameters. We revealed that SO parameters can be extracted accurately via scanning measurements in the diffusive motion of local spin excitation even in the time periods before the appearance of the spin mode.

Chern insulator in a ferromagnetic two-dimensional electron system with Dresselhaus spin–orbit coupling

We propose a Chern insulator in a two-dimensional electron system with Dresselhaus spin–orbit coupling, ferromagnetism, and spin-dependent effective mass. The analytically-obtained topological phase diagrams show the topological phase transitions induced by tuning the magnetization orientation with the Chern number varying between 1, 0, −1. The magnetization orientation tuning shown here is a more practical way of triggering the topological phase transitions than manipulating the exchange coupling that is no longer tunable after the fabrication of the system. The analytic results are confirmed by the band structure and transport calculations, showing the feasibility of this theoretical proposal. With the advanced and mature semiconductor engineering today, this Chern insulator is very possible to be experimentally realized and also promising to topological spintronics.

Effect of illumination on the interplay between Dresselhaus and Rashba spin-orbit couplings in InAs quantum wells

We studied the dependence on carrier density of the spin–orbit coupling (SOC) and of the semiconducting properties of a thin n-type InAs quantum well in the limit of high carrier density, when the second subband starts to populate. Measurements of sheet and Hall resistances were performed in a variable magnetic field, temperature, and under illumination with wavelengths of 400 nm up to 1300 nm. Beats in the Shubnikov de Haas oscillations indicated the presence of strong spin–orbit coupling, and the fast Fourier transforms of the oscillations point toward the presence of both Rashba and Dresselhaus spin–orbit interactions. We used simulations to extract the carrier density dependence of the SOCs, based on the Hamiltonian of a single subband 2D electron system with both types of spin–orbit interactions and subject to a perpendicular magnetic field. The results indicate that the Rashba coefficient decreases with increasing the carrier concentration, with an accelerated decrease close to the transition to double occupancy. The Dresselhaus coefficient is not only smaller but also drops in the proximity of the transition, together with the carrier mobility and the Landau level broadening energy. This behavior is discussed in the context of phenomena associated with the onset of double occupancy and based on intersubband interactions.

Simultaneous evaluation of drift- and diffusion-induced spin-orbit fields in a (001) GaAs/AlGaAs two-dimensional electron gas

We experimentally investigate spatiotemporal dynamics of an electron spin ensemble in the coexistence of drift and diffusive spin motion in a (001) GaAs/AlGaAs two-dimensional electron gas. Electron spins simultaneously experience spin–orbit effective magnetic fields induced by each transport mechanism, resulting in the modulation of spin precession frequency. By employing scanning time-resolved Kerr rotation microscopy, we evaluate both drift and diffusion induced spin–orbit fields simultaneously from the spatiotemporal spin map. Based on the evaluated Rashba and Dresselhaus spin–orbit coefficients, we clarify the difference and the accuracy of the evaluated spin–orbit coefficients in each transport mechanism.

Ground states of spin-orbit-coupled Bose Einstein condensates in the presence of external magnetic field

Two different kinds of spin-orbit (SO) coupling are often investigated theoretically and experimentally in atomic Bose-Einstein condensates (BECs), namely, Rashba and Dresselhaus SO couplings. We show that ground states for these two SO-coupled BECs share lots of similarities and it is impossible to distinguish them from the observation of ground states. We find that an Ioffe-Pritchard magnetic field can be utilized as a tool to distinguish them. In the presence of the Ioffe-Pritchard magnetic field, ground states manifest distinctively for the Rashba and Dresselhaus SO-coupled BECs.

Impacts of external fields and Rashba and Dresselhaus spin–orbit interactions on the optical rectification, second and third harmonic generations of a quantum ring

In the present paper, based on matrix diagonalization method and density matrix approach, the optical rectification (OR), second harmonic and third harmonic generations (SHG and THG) of a GaAs quantum ring (QR) were numerically investigated. To do this purpose, dependency of transition energies and geometrical factors on external magnetic, electric fields and inner radius were analyzed in the presence of Rashba (R) and Dresselhaus (D) spin orbit interactions (SOIs). The outcomes obviously indicate that position and amplitude of OR, SHG and THG peaks experienced intensive depend on external fields, inner radius and interplay of SOIs. These outcomes may be useful due to improvement of spintronics devices.

Closed-Form Weak Localization Magnetoconductivity in Quantum Wells with Arbitrary Rashba and Dresselhaus Spin-Orbit Interactions.

We derive a closed-form expression for the weak localization (WL) corrections to the magnetoconductivity of a 2D electron system with arbitrary Rashba α and Dresselhaus β (linear) and β_{3} (cubic) spin-orbit interaction couplings, in a perpendicular magnetic field geometry. In a system of reference with an in-plane z[over ^] axis chosen as the high spin-symmetry direction at α=β, we formulate a new algorithm to calculate the three independent contributions that lead to WL. The antilocalization is counterbalanced by the term associated with the spin relaxation along z[over ^], dependent only on α-β. The other term is generated by two identical scattering modes characterized by spin-relaxation rates which are explicit functions of the orientation of the scattered momentum. Excellent agreement is found with data from GaAs quantum wells, where, in particular, our theory correctly captures the shift of the minima of the WL curves as a function of α/β. This suggests that the anisotropy of the effective spin-relaxation rates is fundamental to understanding the effect of the spin-orbit coupling in transport.

Designing Rashba\u2013Dresselhaus effect in magnetic insulators

One of the major strategies to control magnetism in spintronics is to utilize the coupling between electron spin and its orbital motion. The Rashba and Dresselhaus spin–orbit couplings induce magnetic textures of band electrons called spin momentum locking, which produces a spin torque by the injection of electric current. However, joule heating had been a bottleneck for device applications. Here, we propose a theory to generate further rich spin textures in insulating antiferromagnets with broken spatial inversion symmetry (SIS), which is easily controlled by a small magnetic field. In antiferromagnets, the ordered moments host two species of magnons that serve as internal degrees of freedom in analogy with electron spins. The Dzyaloshinskii–Moriya interaction introduced by the SIS breaking couples the two-magnon-degrees of freedom with the magnon momentum. We present a systematic way to design such texture and to detect it via magnonic spin current for the realization of antiferromagnetic memory.

Effects of spin–orbit interactions, external fields and eccentricity on the optical absorption of an elliptical quantum ring

In this work, the effects of the Rashba and Dresselhaus spin–orbit interactions, eccentricity and external electric and magnetic fields on the linear optical absorption in an elliptical quantum ring are studied. The electronic structure is determined using the finite element method, and the linear optical absorption coefficient is calculated by the density matrix approach. Results indicate that the spin–orbit interaction and magnetic field lead to the splitting and oscillatory behavior of the energy levels, respectively. The resonant peak of the linear optical absorption shifts to the higher energies with increasing eccentricity. The magnitude and position of the resonant peaks have non-monotonic behaviors with the external fields.

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.

Spin–orbit interaction effects in ZnO/ZnS core–shell and ZnS/ZnO inverted core–shell quantum dots

Rashba and Dresselhaus spin–orbit interactions (SOIs), external fields and dielectric environment effects on hydrogenic impurity states in core–shell (ZnO/ZnS) and inverted core–shell (ZnS/ZnO) quantum dots were studied. We employed the finite difference method to achieve energy eigenvalues of the system. Our results demonstrate that SOIs, external fields and dielectric environment change drastically the impurity states. Besides, the spin degeneracy is removed when both the SOIs and the Zeeman effect are simultaneously considered.

Robustness of a persistent spin helix against a cubic Dresselhaus field in (001) and (110) oriented two-dimensional electron gases

The persistent spin helix (PSH) state in III--V semiconductor quantum wells (QWs) is a promising candidate for spin-based applications because the PSH state realizes controllable spin orientation with long spin lifetime. Although the cubic Dresselhaus spin-orbit (SO) interaction is known for breaking the PSH state in both (001)-oriented and (110)-oriented QWs, it is not well understood how the distinct symmetry of cubic Dresselhaus terms ${\ensuremath{\beta}}_{3}$ between (001) and (110) QWs affects the robustness of the PSH state. Here we investigate robustness of the PSH state between (001) and (110) QWs under various strengths of cubic Dresselhaus SO interaction based on numerical Monte Carlo approach and magnetoconductance simulation, respectively, representing optical spin excitation/detection and weak localization/weak antilocalization in magnetotransport. For electron spins initialized along $z\ensuremath{\parallel}[001]$ in a (001) QW and $x\ensuremath{\parallel}[001]\phantom{\rule{4pt}{0ex}}\mathrm{and}\phantom{\rule{4pt}{0ex}}y\ensuremath{\parallel}[1\overline{1}0]$ in a (110) QW, where the spin distribution is developed with the helical spin mode, a (001) QW shows a more robust PSH state against the increase of ${\ensuremath{\beta}}_{3}$ than does a (110) QW. This phenomenon is contrary to numerically computed magnetoconductance, where weak localization is maintained on the variation of ${\ensuremath{\beta}}_{3}$ in a (110) QW, whereas weak antilocalization appears in a (001) QW. By deriving the spin lifetime of the PSH state in a (110) QW from a diffusion equation using a random-walk approach, we demonstrate that such a difference arises directly from the magnitude and orientation of third angular harmonics in cubic Dresselhaus fields for (001) and (110) QWs.

Effects of Rashba Spin-Orbit Coupling on the Anisotropic Magneto Resistance in Domain Wall

The present paper, based on semi-classical Boltzmann equation, aims to investigate the effects of Rashba and Dresselhaus spin orbit interaction and impurities on domain wall anisotropic magneto resistance. It has been shown that the mentioned effects play a remarkable role in anisotropic magneto resistance of electron current in domain walls. It was also concluded that while an increase in Rashba coupling strength can effectively enhance anisotropic magneto resistance of the domain wall, an increase in the wave-vector and exchange interaction leads to their decrease.

Spin transport properties in a non-uniform quantum wire modulated by both Rashba and Dresselhaus spin–orbit couplings

Spin transport properties in a non-uniform quantum wire (QW) in the presence of both the Rashba and Dresselhaus spin–orbit couplings (SOCs) is investigated by using the non-equilibrium Green's function (NEGF) method combined with the Landauer Büttiker formalism. It is found that such a non-uniform quantum wire exhibits considerable spin polarization in its conductance in the influence of both the Rashba and Dresselhaus SOCs, and that the two SOCs' strengths strongly affect both the magnitude and sign of the electron spin polarization. Interestingly, the Rashba and Dresselhaus SOCs play the same modulating role in the electron spin polarization. The proposed nanostructure can potentially be utilized to devise an all-electrical spintronic device.

The Rashba and Dresselhaus spin-orbit interactions effects on the optical properties of a quantum ring

Influence of Rashba and Dresselhaus spin orbit interactions (SOIs) as well as external magnetic and electric fields on optical behaviors of quantum rings (QRs) were studied. To achieve this purpose, the matrix diagonalization method was exerted to compute energy eigenvalues of the system in the presence of electric and magnetic fields. Besides, the compact density matrix approach was used to calculate the refractive index (RI) and absorption coefficient (AC) of 1 → 2, 1 → 3, 1 → 6 and 3 → 5 transitions. Moreover, by increasing the magnetic (B) and electric (F) fields, energy splitting of intersubband energy levels was increased and thus the RIs and ACs of the system are changed. The results clearly show that, position and peak value of total RIs and ACs curves of all transitions experienced significant change by increasing the magnetic and electric fields in the presence of SOIs. Finally, the effect of size variation on optical RI changes and ACs was studied. The results show that the higher inner radii, R1, is, the stronger quantum confinement and energy increase are. These results are relevant for the designing of spin-based devices.

Quantum anomalous Hall phase in a one-dimensional optical lattice

We propose to simulate and detect quantum anomalous Hall phase with ultracold atoms in a one-dimensional optical lattice, with the other synthetic dimension being realized by modulating spin–orbit coupling. We show that the system manifests a topologically nontrivial phase with two chiral edge states which can be readily detected in this synthetic two-dimensional system. Moreover, it is interesting that at the phase transition point there is a flat energy band and this system can also be in a topologically nontrivial phase with two Fermi zero modes existing at the boundaries by considering the synthetic dimension as a modulated parameter. We also show how to measure these topological phases experimentally in ultracold atoms. Another model with a random Rashba and Dresselhaus spin–orbit coupling strength is also found to exhibit topological nontrivial phase, and the impact of the disorder to the system is revealed.

Effects of Rashba Spin-Orbit Coupling On the Anisotropic Magneto Resistance in Domain Wall -=SUP=-*-=/SUP=-

AbstractThe present paper, based on semi-classical Boltzmann equation, aims to investigate the effects of Rashba and Dresselhaus spin orbit interaction and impurities on domain wall anisotropic magneto resistance. It has been shown that the mentioned effects play a remarkable role in anisotropic magneto resistance of electron current in domain walls. It was also concluded that while an increase in Rashba coupling strength can effectively enhance anisotropic magneto resistance of the domain wall, an increase in the wave-vector and exchange interaction leads to their decrease.

Effect of electric field on the ratio between the rashba and dresselhaus parameters in III–V heterostructures

The size-quantized energy subbands and envelope wave functions for [001] quantum wells based on zinc-blende III–V semiconductors are numerically calculated using the eight-band Kane model and finite-difference discretization scheme in coordinate space. The effect of the quantum-well band parameters and external electric field oriented along the structure growth direction on the ratio between the Rashba and Dresselhaus spin–orbit coupling parameters is studied. It is demonstrated that at certain electric-field values the spin–orbit coupling parameters in GaAs/InGaAs structures can be equal, which ensures the condition for forming stable spin helices. In addition, it is established that the spin–orbit coupling linear in wave vector in symmetric GaAs/InGaAs wells can disappear under certain well widths and barrier chemical compositions.