Genuine topological Anderson insulator from impurity induced chirality reversal

TL;DR

This paper demonstrates that impurity-induced effects can reverse the chirality of topological mass in Dirac fermions, leading to a genuine topological Anderson insulator, supported by analytical and numerical methods.

Contribution

It reveals a novel mechanism where impurity scattering reverses topological chirality, creating a new phase called the topological Anderson insulator, with comprehensive analytical and numerical validation.

Findings

Impurity scattering can reverse the sign of the Chern number.

A phase disconnected from the clean topological phase is induced by disorder.

The tri-critical point occurs at zero impurity density, linked to a zero energy bound state.

Abstract

We investigate a model of Dirac fermions with Haldane type mass impurities which open a global topological gap even in the dilute limit. Surprisingly, we find that the chirality of this mass term, i.e., the sign of the Chern number, can be reversed by tuning the magnitude of the single-impurity scattering. Consequently, the disorder induces a phase disconnected from the clean topological phase, i.e., a genuine topological Anderson insulator. In seeming contradiction to the expectation that mass disorder is an irrelevant perturbation to the clean integer quantum Hall transition, the tri-critical point separating these two Chern insulating phases and a thermal metal phase is located at zero impurity density and connected to the appearance of a zero energy bound state in the continuum corresponding to a divergent Haldane mass impurity. Our conclusions based on the T-matrix expansion are substantiated by large scale Chebyshev-Polynomial-Green-Function numerics. We discuss possible experimental platforms.