Topological Anderson insulators in two-dimensional non-Hermitian disordered systems

TL;DR

This paper explores how non-Hermitian effects like nonreciprocal hopping and gain-loss influence topological phases and localization in disordered two-dimensional Chern insulators, revealing the existence of topological Anderson insulators under these conditions.

Contribution

It introduces a numerical approach to map topological phases in non-Hermitian disordered systems and demonstrates the persistence of topological Anderson insulators with different non-Hermitian effects.

Findings

Nonreciprocal hopping enlarges topological regions.

Gain-and-loss effects reduce topological regions.

Topological Anderson insulators can exist under both non-Hermiticities.

Abstract

The interplay among topology, disorder, and non-Hermiticity can induce some exotic topological and localization phenomena. Here we investigate this interplay in a two-dimensional non-Hermitian disordered Chern-insulator model with two typical kinds of non-Hermiticities, the nonreciprocal hopping and on-site gain-and-loss effects. The topological phase diagrams are obtained by numerically calculating two topological invariants in the real space, which are the disorder-averaged open-bulk Chern number and the generalized Bott index, respectively. We reveal that the nonreciprocal hopping (the gain-and-loss effect) can enlarge (reduce) the topological regions and the topological Anderson insulators induced by disorders can exist under both kinds of non-Hermiticities. Furthermore, we study the localization properties of the system in the topologically nontrivial and trivial regions by using the inverse participation ratio and the expansion of single particle density distribution.