Abstract
Spin transport was studied in a two-dimensional electron gas hosted in a wide GaAs quantum well occupying two subbands. Using space and time Kerr rotation microscopy to image drifting spin packets under an in-plane accelerating electric field, optical injection and detection of spin polarization were achieved in a pump–probe configuration. The experimental data exhibited high spin mobility and long spin lifetimes allowing us to obtain the spin–orbit fields as a function of the spin velocities. Surprisingly, above moderate electric fields of 0.4 V/cm with velocities higher than 2 µm/ns, we observed a dependence of both bulk and structure-related spin–orbit interactions on the velocity magnitude. A remarkable feature is the increase in the cubic Dresselhaus term to approximately half of the linear coupling when the velocity is raised to 10 µm/ns. In contrast, the Rashba coupling for both subbands decreases to about half of its value in the same range. These results yield new information on the application of drift models in spin–orbit fields and about limitations for the operation of spin transistors.
Highlights
Over the past few decades, the quest to build spintronic analogs to conventional charge-based electronic devices has motivated intense research.1–5 Paramount to this search is the spin transistor, proposed by Datta and Das,6 that uses a gate-tunable Rashba spin–orbit interaction (SOI)7 for the electric manipulation of the spin state inside a ballistic channel
Later studies included the Dresselhaus SOI8 so that a non-ballistic transistor robust against spinindependent scattering could be realized.9–12. When both Rashba and Dresselhaus spin-orbit couplings (SOCs) have equal magnitudes (α = β), a uniaxial spin–orbit field is formed and the spin polarization could be preserved during transport
Cubic spin–orbit fields impose relevant constrains in spin transistor proposals that target extended coherence, demanding particular attention. We addressed this issue in the investigation of a 2DEG confined in a GaAs quantum well (QW) with two occupied subbands
Summary
Over the past few decades, the quest to build spintronic analogs to conventional charge-based electronic devices has motivated intense research. Paramount to this search is the spin transistor, proposed by Datta and Das, that uses a gate-tunable Rashba spin–orbit interaction (SOI) for the electric manipulation of the spin state inside a ballistic channel. Over the past few decades, the quest to build spintronic analogs to conventional charge-based electronic devices has motivated intense research.1–5 Paramount to this search is the spin transistor, proposed by Datta and Das, that uses a gate-tunable Rashba spin–orbit interaction (SOI) for the electric manipulation of the spin state inside a ballistic channel. We are interested in the investigation of driftinduced SOC modifications by exploring a two-dimensional electron gas (2DEG) hosted in a wide GaAs quantum well (QW) with two-occupied subbands Previous studies in such multilayer systems show high charge mobility and long spin lifetimes as well as the possibility to generate current-induced spin polarization.. Scitation.org/journal/adv assumption of constant spin–orbit couplings independent of the velocity range of the spin transistor operation
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