Magnetoconductance of the quantum spin Hall state

TL;DR

This paper investigates how nonmagnetic disorder and magnetic fields affect the conductance of quantum spin Hall edges, revealing a linear deviation from quantization and proposing a disorder-dependent crossover scenario.

Contribution

It introduces a dimensional crossover model explaining edge conductance behavior under disorder and magnetic fields in quantum spin Hall insulators.

Findings

Conductance deviates linearly with magnetic field at small B.

Weak disorder preserves 1D edge behavior, strong disorder induces 2D diffusive motion.

Proposes a crossover from 1D to 2D transport regimes depending on disorder strength.

Abstract

We study numerically the edge magnetoconductance of a quantum spin Hall insulator in the presence of quenched nonmagnetic disorder. For a finite magnetic field B and disorder strength W on the order of the bulk gap E_g, the conductance deviates from its quantized value in a manner which appears to be linear in |B| at small B. The observed behavior is in qualitative agreement with the cusp-like features observed in recent magnetotransport measurements on HgTe quantum wells. We propose a dimensional crossover scenario as a function of W, in which for weak disorder W < E_g the edge liquid is analogous to a disordered spinless 1D quantum wire, while for strong disorder W > E_g, the disorder causes frequent virtual transitions to the 2D bulk, where the originally 1D edge electrons can undergo 2D diffusive motion and 2D antilocalization.