Spin polarization in biased Rashba-Dresselhaus two-dimensional electron systems

TL;DR

This paper investigates how electric fields induce spin polarization in a 2D electron system with Rashba and Dresselhaus spin-orbit coupling, highlighting weakly damped spin excitations when these couplings are equal.

Contribution

It provides a rigorous derivation of spin-charge coupled drift-diffusion equations and analyzes spin dynamics, especially in the case of equal Rashba and Dresselhaus couplings.

Findings

Identification of weakly damped spin excitations

Suppressed spin relaxation in equal Rashba-Dresselhaus systems

Electric-field-induced spin polarization dynamics

Abstract

Based on spin-charge coupled drift-diffusion equations, which are derived from kinetic equations for the spin-density matrix in a rigorous manner, the electric-field-induced nonequilibrium spin polarization is treated for a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling. Most emphasis is put on the consideration of the field-mediated spin dynamics for a model with equal Rashba and Dresselhaus coupling constants, in which the spin relaxation is strongly suppressed. Weakly damped electric-field-induced spin excitations are identified, which remind of space-charge waves in crystals.