Breakdown of topological protection due to non-magnetic edge disorder in two-dimensional materials in the Quantum Spin Hall phase

TL;DR

This paper investigates how non-magnetic edge disorder combined with electron interactions can break topological protection in 2D quantum spin Hall systems, leading to conductance deviations and suppression.

Contribution

It demonstrates that edge disorder induces local magnetic moments that break time-reversal symmetry, causing breakdown of topological protection in 2D materials.

Findings

Edge disorder causes conductance deviations in short samples.

Long samples experience strong conductance suppression.

Edge defects induce local magnetic moments that break topological protection.

Abstract

We study the suppression of the conductance quantization in quantum spin Hall systems by a combined effect of electronic interactions and edge disorder, that is ubiquitous in exfoliated and CVD grown 2D materials. We show that the interplay between the electronic localized states due to edge defects and electron-electron interactions gives rise to local magnetic moments, that break time-reversal symmetry and the topological protection of the edge states in 2D topological systems. Our results suggest that edge disorder leads to small deviations of a perfect quantized conductance in short samples and to a strong conductance suppression in long ones. Our analysis is based on on the Kane-Mele model, an unrestricted Hubbard mean field Hamiltonian and on a self-consistent recursive Green's functions technique to calculate the transport quantities.