Transport through a disordered topological-metal strip

TL;DR

This paper investigates how disorder affects conductance in a topological-metal strip, revealing a non-monotonic behavior where conductance initially drops then recovers and saturates below the quantized value, highlighting the robustness of edge states.

Contribution

It combines numerical lattice simulations and analytical models to show the disorder-induced conductance behavior in topological-metal systems, a novel insight into their transport properties.

Findings

Conductance initially decreases with disorder from its quantized value.

Conductance recovers and saturates below the quantized level at higher disorder.

Edge states remain delocalized while bulk states tend to localize with increasing disorder.

Abstract

Features of a topological phase, and edge states in particular, may be obscured by overlapping in energy with a trivial conduction band. The topological nature of such a conductor, however, is revealed in its transport properties, especially in the presence of disorder. In this work, we explore the conductance behavior of such a system with disorder present, and contrast it with the quantized conductance in an ideal 2D topological insulator. Our analysis relies on numerics on a lattice system and analytics on a simple toy model. Interestingly, we find that as disorder is increased from zero, the edge conductivity initially falls from its quantized value; yet as disorder continues to increase, the conductivity recovers, and saturates at a value slightly below the quantized value of the clean system. We discuss how this effect can be understood from the tendency of the bulk states to localize, while the edge states remain delocalized.