Helical edge states induced by lateral spin-orbit coupling

TL;DR

This paper proposes a mechanism for creating dissipationless helical edge states in 2D topological insulators through strong lateral spin-orbit coupling at edges, independent of band inversion.

Contribution

It introduces a novel approach where strong edge spin-orbit coupling induces protected helical edge states without requiring band inversion.

Findings

Strong edge SOC can generate helical edge states.

Helical states penetrate the band gap and are isolated from bulk states.

System exhibits topological insulator behavior due to edge effects.

Abstract

The presence of edges locally breaks the inversion symmetry of heterostructures and gives rise to lateral (edge) spin-orbit coupling (SOC), which, under some conditions, can lead to the formation of helical edge states. If the edge SOC is strong enough, the helical edge states can penetrate the band-gap and be energetically isolated from the bulk-like states. As a result backward scattering is suppressed, dissipationless helical edge channels protected against time-inversion symmetric perturbations emerge, and the system behaves as a 2D topological insulator (TI). However, unlike in previous works on TIs, the mechanism proposed here for the creation of protected helical edge states relies on the strong edge SOC rather than on band inversion.