Edge Dynamics in a Quantum Spin Hall State: Effects from Rashba Spin-Orbit Interaction

TL;DR

This paper investigates how spatially varying Rashba spin-orbit interactions affect the edge modes of a quantum spin Hall state, revealing localization and insulating behavior under certain conditions, with implications for experimental transport measurements.

Contribution

It introduces the effects of non-uniform Rashba spin-orbit coupling on edge state dynamics, showing how disorder and periodic modulation influence localization and transport.

Findings

Random Rashba coupling causes edge mode localization.

Periodic Rashba modulation can induce edge insulating states.

Edge transport is sensitive to the strength and pattern of Rashba interactions.

Abstract

We analyze the dynamics of the helical edge modes of a quantum spin Hall state in the presence of a spatially non-uniform Rashba spin-orbit (SO) interaction. A randomly fluctuating Rashba SO coupling is found to open a scattering channel which causes localization of the edge modes for a weakly screened electron-electron (e-e) interaction. A periodic modulation of the SO coupling, with a wave number commensurate with the Fermi momentum, makes the edge insulating already at intermediate strengths of the e-e interaction. We discuss implications for experiments on edge state transport in a HgTe quantum well.