Gate-induced spin precession in an In<sub>0.53</sub>Ga<sub>0.47</sub>As two dimensional electron gas

Bournel, A.; Dollfus, Philippe; Bruno, P.; Hesto, P.

doi:10.1051/epjap:1998238

Cited by 61 publications

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“…The maximum spin relaxation time occurs when the width is of the order of the bulk spin relaxation length. Remarkably, while the tendency to suppress spin relaxation in confined systems has been predicted in a number of theoretical works, [4][5][6][7][8][9][10] there has been no anticipation of the increase of the spin relaxation observed at the smallest widths. In this paper we show that spin active boundaries, not considered in the previous theoretical analysis, dramatically change the size dependence of the spin relaxation time in the small width limit and provide a useful point of view as far as the interpretation of the experiment is concerned.…”

Section: Introductionmentioning

confidence: 99%

Spin relaxation in narrow wires of a two-dimensional electron gas

et al. 2006

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How does an initially homogeneous spin polarization in a confined two-dimensional electron gas with Rashba spin-orbit coupling evolve in time? How does the relaxation time depend on system size? We study these questions for systems of a size that is much larger than the Fermi wavelength, but comparable and even shorter than the spin relaxation length. Depending on the confinement spin relaxation may become faster or slower than in the bulk. An initially homogeneously polarized spin system evolves into a spiral pattern.

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Section: Introductionmentioning

confidence: 99%

Spin relaxation in narrow wires of a two-dimensional electron gas

et al. 2006

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“…For strong enough spin relaxation, the drain current is that of an unpolarized beam. The predominant spin-dephasing mechanism in spin transistors is that of the Dyakonov-Perel type [8,9], due to the largest of the two s-o terms [10]. The "on state" of our device operates with a gate bias for which α = β.…”

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confidence: 99%

Nonballistic Spin-Field-Effect Transistor

2003

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We propose a spin field-effect transistor based on spin-orbit (s-o) coupling of both the Rashba and the Dresselhaus types. Differently from earlier proposals, spin transport through our device is tolerant against spin-independent scattering processes. Hence the requirement of strictly ballistic transport can be relaxed. This follows from a unique interplay between the Dresselhaus and the (gate-controlled) Rashba interactions; these can be tuned to have equal strengths thus yielding kindependent eigenspinors even in two dimensions. We discuss implementations with two-dimensional devices and quantum wires. In the latter, our setup presents strictly parabolic dispersions which avoids complications arising from anticrossings of different bands.In the recent years research in semiconductor physics has been focused on the emerging field of spintronics. This key word refers to the variety of efforts to use the electron spin rather than, or in combination with, its charge for information processing; or, even more ambitiously, quantum information processing [2]. Among the most prominent device proposals is the spin field-effect transistor (FET) due to Datta and Das [3]. This proposal uses the Rashba spin-orbit coupling to perform controlled rotations of spins of electrons passing through an FETtyped device. This particular spin-orbit interaction is due to the inversion-asymmetry of the confining potential and is of the form [4]where p is the momentum of the electron confined in a two-dimensional geometry, and σ the vector of Pauli matrices. The coefficient α is tunable in strength by the external gate of the FET. Due to the dependence on the momentum, the Rashba spin-orbit coupling can be viewed as a wave vector-dependent Zeeman field which can change drastically if the electron is scattered into a different momentum state. Therefore, such scattering events readily randomize the electron spin thus limiting the range of operation of the Datta-Das spin-FET to the regime of ballistic transport where such processes do not occur.In the present work we propose a modified version of the spin-FET in which the electrons are not only subject to spin-orbit interaction of the Rashba but also of the Dresselhaus type [5]. The latter is present in semiconductors lacking bulk inversion symmetry. When restricted to a two-dimensional semiconductor nanostruture with appropriate growth geometry this coupling is of the form [6,7] where the coefficient β is determined by the semiconductor material and the geometry of the sample. Below we show that our proposed device is robust against spin-independent scattering and hence can also operate in a non-ballistic (or diffusive) regime. This unique feature follows from the possibility of tuning the Rashba (via proper gating) and the Dresselhaus terms so that they have equal strengths α = β. In this case, we show quite generally below that the electron spinor is k-independent in two dimensions -even in the presence of (spin-independent) scatterers. Tuned Rashba and Dresselhaus terms. Consider the Ham...

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“…This is demonstrated in the present Communications. In principle, the two effects of the gate, changing field strength and density, can be separated experimentally by varying the voltage at a front gate and a back gate independently [11].Usually, Rashba spin precession is described as a band structure effect, resulting from spin splitting [2,4], as calculated in the original work by Rashba [3] for the homogeneous two-dimensional case. Such a single particle approach, however, cannot account for electron-electron interactions.…”

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confidence: 99%

Rashba precession in quantum wires with interaction

Häusler

2001

Phys. Rev. B

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Rashba precession of spins moving along a one-dimensional quantum channel is calculated, accounting for Coulomb interactions. The Tomonaga-Luttinger model is formulated in the presence of spin-orbit scattering and solved by Bosonization. Increasing interaction strength at decreasing carrier density is found to enhance spin precession and the nominal Rashba parameter due to the decreasing spin velocity compared with the Fermi velocity. This result can elucidate the observed pronounced changes of the spin splitting on applied gate voltages which are estimated to influence the interface electric field in heterostructures only little. : 71.10.Pm, 71.70.Ej, 73.20.Dx According to recent speculations spin could replace the electric charge to carry information in future electronic devices [1]. The 'spin transistor' proposed by Datta and Das [2] might switch faster than traditional transistors since during operation it avoids redistributing charges. The idea is based on the Rashba effect [3] which causes spins to precess as they move along a heterostructure [4] so that the conductance depends on the final spin orientation relative to the magnetization of the ferromagnetic drain contact [5,6]. The strength of the Rashba effect is proportional to the electric field acting perpendicular to the electron plane which, when varied by a gate, changes the final spin orientation and thus the transport properties of the device. Advantage is taken of long spin coherence times and lengths [7], found in semiconductors. In the attempt of experimental realization considerable progress has been achieved meanwhile to inject finite spin densities [8]. Polarizations of 90% have been reported in GaAs [9]. PACSBeating patterns varying with gate voltages have indeed been observed in Shubnikov-de Haas (SdH) measurements [10][11][12]. Estimates show, however, that the the gate voltage adds an electric field contribution to a much stronger intrinsic field at the interface which does not suffice to explain the observed variations in spin splittings by a factor of two. One should notice that the gate voltage not only changes the strength of the electric field but at the same time it also alters the carrier density in the heterostructure as is directly monitored by the SdH oscillations. Without interactions this would not change the Rashba precession within the effective mass approximation [13] but, since particularly in semiconductors the strength of Coulomb interactions change with density through the r s -parameter, the question arises whether interactions influence the Rashba precession. This is demonstrated in the present Communications. In principle, the two effects of the gate, changing field strength and density, can be separated experimentally by varying the voltage at a front gate and a back gate independently [11].Usually, Rashba spin precession is described as a band structure effect, resulting from spin splitting [2,4], as calculated in the original work by Rashba [3] for the homogeneous two-dimensional case. Such a single particle a...

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Gate-induced spin precession in an In_0.53Ga_0.47As two dimensional electron gas

Cited by 61 publications

References 0 publications

Spin relaxation in narrow wires of a two-dimensional electron gas

Spin relaxation in narrow wires of a two-dimensional electron gas

Nonballistic Spin-Field-Effect Transistor

Rashba precession in quantum wires with interaction

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Gate-induced spin precession in an In0.53Ga0.47As two dimensional electron gas

Cited by 61 publications

References 0 publications

Spin relaxation in narrow wires of a two-dimensional electron gas

Spin relaxation in narrow wires of a two-dimensional electron gas

Nonballistic Spin-Field-Effect Transistor

Rashba precession in quantum wires with interaction

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Gate-induced spin precession in an In_0.53Ga_0.47As two dimensional electron gas