Localization and Mobility Gap in Topological Anderson Insulator

TL;DR

This paper investigates the physical mechanisms behind the topological Anderson insulator, revealing that disorder induces a topologically non-trivial phase protected by a mobility gap, distinct from conventional band gaps.

Contribution

It provides a detailed analysis of the origin of TAI, showing how disorder leads to a topological phase via band touching and characterizing the mobility gap as a cluster of subgaps.

Findings

Disorder induces a topologically non-trivial phase in HgTe/CdTe quantum wells.

The TAI is protected by a mobility gap, not a band gap.

The mobility gap consists of non-trivial subgaps separated by localized bands.

Abstract

It has been proposed that disorder may lead to a new type of topological insulator, called topological Anderson insulator (TAI). Here we examine the physical origin of this phenomenon. We calculate the topological invariants and density of states of disordered model in a super-cell of 2-dimensional HgTe/CdTe quantum well. The topologically non-trivial phase is triggered by a band touching as the disorder strength increases. The TAI is protected by a mobility gap, in contrast to the band gap in conventional quantum spin Hall systems. The mobility gap in the TAI consists of a cluster of non-trivial subgaps separated by almost flat and localized bands.