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

Iizasa, Daisuke; Sato, Dai; Morita, Ken; Nitta, Junsaku; Kohda, Makoto

doi:10.1103/physrevb.98.165112

Cited by 10 publications

(11 citation statements)

References 29 publications

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“…To solve this problem, the persistent spin helix (PSH) state has been proposed theoretically , and realized experimentally, , where the orientation of the SO field is unidirectional and momentum-independent. To date, most schemes to realize PSH states rely on precise control of the relative strength of the Rashba and Dresselhaus SO interactions in III–V semiconductor quantum wells. − When the strengths of the Rashba and the Dresselhaus SOC become equal (λ R = λ D ), the combined SO field is aligned in a uniaxial direction with SU(2) symmetry, which is robust against spin-independent scattering and renders the spin lifetime ultimately infinite. , Despite the advantages of the PSH states, the stringent condition of λ R = λ D is difficult to satisfy because it requires matched quantum well width and doping level as well as the application of an external gate bias, which limit the applications of the PSH states to realistic devices. , Additionally, it has been demonstrated that the PSH states can also be achieved in specific noncentrosymmetric bulk materials where the PSH state is enforced by the nonsymmorphic space group symmetry of the crystal . However, these states survive only along certain high-symmetry paths in the Brillouin zone and are likely overwhelmed by other non-PSH states in the same energy window, which severely hamper their practical applications.…”

mentioning

confidence: 99%

Unidirectional Spin–Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices

Zhang

Huang

et al. 2019

Nano Lett.

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Spin–orbit (SO) interaction is an indispensable element in the field of spintronics for effectively manipulating the spin of carriers. However, in crystalline solids, the momentum-dependent SO effective magnetic field generally results in spin randomization by a process known as the Dyakonov–Perel spin relaxation, leading to the loss of spin information. To overcome this obstacle, the persistent spin helix (PSH) state with a unidirectional SO field was proposed but difficult to achieve in real materials. Here, on the basis of first-principles calculations and tight-binding model analysis, we report for the first time a unidirectional SO field in monolayer transition metal dichalcogenides (TMDs, MX2, M = Mo, W; and X = S, Se) induced by two parallel chalcogen vacancy lines. By changing the relative positions of the two vacancy lines, the direction of the SO field can be tuned from x to y . Moreover, using k · p perturbation theory and group theory analysis, we demonstrate that the emerging unidirectional SO field is subject to both the structural symmetry and 1D nature of such defects engineered in 2D TMDs. In particular, through transport calculations, we confirm that the predicted SO states carry highly coherent spin current. Our findings shed new light on creating PSH states for high-performance spintronic devices.

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mentioning

confidence: 99%

Unidirectional Spin–Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices

Zhang

Huang

et al. 2019

Nano Lett.

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“…Firstly, the [110] direction shows a less robust spin texture compared to [001], being consistent with previous calculation. 39 Secondly, the salient vanishing of 1/τ hel at [111] results from the existence of a homogeneous persistent spin texture as Ω psh = 0 and Ω 3 is collinear with the [111] axis. Since both excited and detected spin textures contain a finite component parallel to [111], the extracted spin relaxation rate corresponds to the homogeneous texture and not to a helical one.…”

Section: Spin Diffusion Equationmentioning

confidence: 99%

“…For this reason, we only observe weak localization even for a large k-cubic SO field in [110] quantum wells due to the presence of persistent homogenous spin textures. 39,41 Here, observing a crossover to weak antilocalization requires the breaking of the PSH condition Γ 0 via an increasing Rashba term. 41 Similarly, we can expect the extraordinary small relaxation rates of the homogeneous spin textures for growth directions between [111] and [110] to prevent the emergence of the weak antilocalization features.…”

Section: E Experimental Accessibilitymentioning

confidence: 99%

“…As a consequence, the geometrical relations between the collinear and the symmetry-breaking part of the total SO field are complicated and the induced relaxation effect is sensitive to the orientation of the quantum well. Previous studies on the impact of the k-cubic Dresselhaus SO field on the stability of the PSH are restricted to the well-established cases of [001], 23,[28][29][30][31][32][33][34][35][36] [110], [37][38][39] and [111] 40 quantum wells.…”

Section: Introductionmentioning

confidence: 99%

“…These often correspond to homogeneous spin textures whose extraordinary long lifetimes prevent the emergence of the weak-antilocalization features necessary for reliable parameter fitting as it is the case, for instance, in [110] and [111] quantum wells. 15,39,41 The supplementing analysis of the spin diffusion equation grants insight into the underlying physical mechanisms and allows us to derive an analytic expression for the general PSH lifetime and the special growth directions.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced longevity of the spin helix in low-symmetry quantum wells

Iizasa,

Kohda,

Zülicke

et al. 2020

Preprint

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In a semiconductor, collective excitations of spin textures usually decay rather fast due to D'yakonov-Perel' spin relaxation. The latter arises from spin-orbit coupling, which induces wavevector (k) dependent spin rotations that, in conjunction with random disorder scattering, generate spin decoherence. However, symmetries occurring under certain conditions can prevent the relaxation of particular homogeneous and inhomogeneous spin textures. The inhomogeneous spin texture, termed as persistent spin helix, is especially appealing as it enables us to manipulate the spin orientation while retaining a long spin lifetime. Recently, it was predicted that such symmetries can be realized in zinc-blende two-dimensional electron gases if at least two growth-direction Miller indices agree in modulus and the coefficients of the Rashba and k-linear Dresselhaus spin-orbit couplings are suitably matched [Kammermeier et al., Phys. Rev. Lett. 117, 236801 (2016)]. In the present paper, we systematically analyze the impact of the symmetry-breaking k-cubic Dresselhaus spin-orbit coupling, which generically coexists in these systems, on the stability of the emerging spin helices with respect to the growth direction. We find that, as an interplay between orientation and strength of the effective magnetic field induced by the k-cubic Dresselhaus terms, the spin relaxation is weakest for a low-symmetry growth direction that can be well approximated by a [225] lattice vector. These quantum wells yield a 30% spin-helix lifetime enhancement compared to [001]-oriented electron gases and, remarkably, require a negligible Rashba coefficient. The rotation axis of the corresponding spin helix is only slightly tilted out of the quantum-well plane. This makes the experimental study of the spin helix dynamics readily accessible for conventional optical spin orientation measurements where spins are excited and detected along the quantum-well growth direction.

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Spin–Orbit Coupling in 2D Semiconductors: A Theoretical Perspective

Chen

et al. 2021

J. Phys. Chem. Lett.

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This theoretical Perspective reviews spin−orbit coupling (SOC), including the Rashba effect and Dresselhaus effect, in two-dimensional (2D) semiconductors. We first introduce the origin of the Rashba effect and Dresselhaus effect using the Hamiltonian models; we then summarize 2D Rashba semiconductors predicted by first-principles density functional theory (DFT) calculations, including AB binary monolayers, Janus monolayers, 2D perovskites, and so on. We also review various manipulating techniques of the Rashba effect on 2D semiconductors, such as external electric field, strain engineering, charge doping, interlayer interactions, proximity effect of substrates, and external magnetic field. We then briefly summarize the applications of SOC, including the generation, detection, and manipulation of spin currents in spin Hall effect transistors and spin field effect transistors. Finally, we conclude this Perspective and propose three promising research fields of SOC in low-dimensional semiconductors, including the nonlinear SOC Hamiltonian model, 2D ferroelectric SOC semiconductors, and 1D Rashba model and semiconductors. This theoretical Perspective enriches the fundamental understanding of SOC in 2D semiconductors and will help in the design of new types of spintronic devices in future experiments.

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

Cited by 10 publications

References 29 publications

Unidirectional Spin–Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices

Unidirectional Spin–Orbit Interaction Induced by the Line Defect in Monolayer Transition Metal Dichalcogenides for High-Performance Devices

Enhanced longevity of the spin helix in low-symmetry quantum wells

Spin–Orbit Coupling in 2D Semiconductors: A Theoretical Perspective

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