Field control of anisotropic spin transport and spin helix dynamics in a modulation-doped GaAs quantum well

Abstract

Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation microspectroscopy, 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 ${\ensuremath{\lambda}}_{\mathrm{SOI}}$ is defined as one complete precession in the effective magnetic field. It is observed that application of (i) an out-of-plane electric field changes the spin decay time and ${\ensuremath{\lambda}}_{\mathrm{SOI}}$ through the Rashba component of the spin-orbit coupling, (ii) an in-plane magnetic field allows for extraction of the Dresselhaus and Rashba parameters, and (iii) an in-plane electric field markedly modifies both the ${\ensuremath{\lambda}}_{\mathrm{SOI}}$ and diffusion coefficient.