Gate-Control of Anisotropic Spin Transport and Spin Helix Dynamics in a Modulation-Doped GaAs Quantum Well

TL;DR

This study explores how electric and magnetic fields influence spin transport and dynamics in high-mobility GaAs quantum wells, revealing tunable spin precession and diffusion properties with experimental and simulation insights.

Contribution

It demonstrates electric and magnetic field control of spin transport and spin helix dynamics in modulation-doped GaAs quantum wells, extending understanding of spin-orbit interactions.

Findings

Electric fields modify spin decay time and precession length.

Magnetic fields enable extraction of spin-orbit parameters.

Electric fields significantly alter spin diffusion and precession.

Abstract

Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation micro-spectroscopy, supported by qualitative kinetic theory simulations of spin diffusion and transport. Evolution of the spins is governed by the Dresselhaus bulk and Rashba structural inversion asymmetries, which manifest as an effective magnetic field that can be extracted directly from the experimental coherent spin precession. A spin precession length L-SOI is defined as one complete precession in the effective magnetic field. It is observed that application of (a) an out-of-plane electric field changes the spin decay time and L-SOI through the Rashba component of the spin-orbit coupling, (b) an in-plane magnetic field allows for extraction of the Dresselhaus and Rashba parameters, and (c) an in-plane electric field markedly modifies both the L-SOI and diffusion coefficient. While simulations reproduce the main features of the experiments, the latter results exceed the corresponding simulations and extend previous studies of drift-current-dependent spin-orbit interactions.