Robustness of Helical Edge States Under Edge Reconstruction

TL;DR

This paper investigates how edge reconstruction and interactions affect the robustness of helical edge states in topological insulators, finding that spin-orbit coupling preserves near-quantized conductance despite potential disruptions.

Contribution

It demonstrates that random spin-orbit coupling suppresses spin polarization, maintaining edge conduction robustness even with edge reconstruction and interactions.

Findings

Interaction effects are well described by the Luttinger liquid model.

Random spin-orbit coupling suppresses dynamical spin polarization.

Edge conduction remains near quantized despite edge reconstruction.

Abstract

The helical edge states of time-reversal invariant two-dimensional topological insulators are protected against backscattering in idealized models. In more realistic scenarios with a shallow confining potential at the sample boundary, additional strongly interacting edge states may arise, that could interfere with the topological protection of edge conduction. We find that interaction effects within the reconstructed edges are well described by the Luttinger liquid model. While interactions between this Luttinger liquid and the helical edge states can in principle give rise to dynamical spin polarization and the breaking of time-reversal symmetry, we demonstrate that random spin-orbit coupling strongly suppresses such dynamical spin polarization, resulting in the persistence of near quantized edge conduction.