Coulomb-induced Rashba spin-orbit coupling in semiconductor quantum wells

TL;DR

This paper investigates how Coulomb interactions induce Rashba spin-orbit coupling in semiconductor quantum wells, enabling control over spin relaxation through voltage tuning.

Contribution

It demonstrates a method to engineer quantum wells where Coulomb-induced Rashba SOI can be modulated to trigger spin relaxation at specific voltages.

Findings

Electrons in the first subband conserve spin along the growth axis.

Electrons in the second subband experience Rashba-induced spin precession.

A threshold voltage V* can switch on spin relaxation mechanisms.

Abstract

In the absence of an external field, the Rashba spin-orbit interaction (SOI) in a two-dimensional electron gas in a semiconductor quantum well arises entirely from the screened electrostatic potential of ionized donors. We adjust the wave functions of a quantum well so that electrons occupying the first (lowest) subband conserve their spin projection along the growth axis (Sz), while the electrons occupying the second subband precess due to Rashba SOI. Such a specially designed quantum well may be used as a spin relaxation trigger: electrons conserve Sz when the applied voltage (or current) is lower than a certain threshold V*; higher voltage switches on the Dyakonov-Perel spin relaxation.