Disordered weak and strong topological insulators

TL;DR

This paper presents a numerical study of disordered topological insulators, revealing unexpected conductance quantization at phase boundaries and identifying two subregions within weak topological insulators with distinct surface state behaviors.

Contribution

It uncovers the robustness of conductance peaks against disorder and characterizes two subregions in weak topological insulators using Lyapunov exponents.

Findings

Robust conductance peaks at phase boundaries despite disorder

Emergence of two subregions in weak topological insulators

Surface states are either robust or suppressed depending on the subregion

Abstract

A global phase diagram of disordered weak and strong topological insulators is established numerically. As expected, the location of the phase boundaries is renormalized by disorder, a feature recognized in the study of the so-called topological Anderson insulator. Here, we report unexpected quantization, i.e., robustness against disorder of the conductance peaks on these phase boundaries. Another highlight of the work is on the emergence of two subregions in the weak topological insulator phase under disorder. According to the size dependence of the conductance, the surface states are either robust or "defeated" in the two subregions. The nature of the two distinct types of behavior is further revealed by studying the Lyapunov exponents.