Failure of conductance quantization in two-dimensional topological insulators due to non-magnetic impurities

TL;DR

This paper explains why conductance quantization fails in two-dimensional topological insulators with non-magnetic impurities, highlighting the role of electron interactions creating effective magnetic scatterers that cause backscattering.

Contribution

It introduces a mechanism where non-magnetic impurities combined with electron interactions induce magnetic scattering, explaining conductance deviations in topological insulators.

Findings

Quantized conductance breaks down in short channels due to impurity effects.

Electron-electron interactions can induce magnetic scattering from non-magnetic impurities.

The theory aligns with experimental observations in atomically thin topological insulators.

Abstract

Despite topological protection and the absence of magnetic impurities, two-dimensional topological insulators display quantized conductance only in surprisingly short channels, which can be as short as 100 nm for atomically thin materials. We show that the combined action of short-range nonmagnetic impurities located near the edges and on site electron-electron interactions effectively creates noncollinear magnetic scatterers, and, hence, results in strong backscattering. The mechanism causes deviations from quantization even at zero temperature and for a modest strength of electron-electron interactions. Our theory provides a straightforward conceptual framework to explain experimental results, especially those in atomically thin crystals, plagued with short-range edge disorder.