# Non-Hermitian Topological Anderson Insulators

## TL;DR

This paper explores how non-Hermiticity influences disordered topological systems, revealing that it can enhance topological phases and induce unique non-Hermitian topological Anderson insulators with localized edge states.

## Contribution

It introduces the concept of non-Hermitian topological Anderson insulators and demonstrates how non-Hermiticity can stabilize topological phases against disorder effects.

## Key findings

- Non-Hermiticity enhances topological phase stability against disorder.
- Discovery of a new topological phase emerging under combined non-Hermiticity and disorder.
- Localization behavior is non-monotonous and linked to Anderson transitions.

## Abstract

Non-Hermitian systems can exhibit unique topological and localization properties. Here we elucidate the non-Hermitian effects on disordered topological systems by studying a non-Hermitian disordered Su-Schrieffer-Heeger model with nonreciprocal hoppings. We show that the non-Hermiticity can enhance the topological phase against disorders by increasing energy gaps. Moreover, we uncover a topological phase which emerges only under both moderate non-Hermiticity and disorders, and is characterized by localized insulating bulk states with a disorder-averaged winding number and zero-energy edge modes. Such topological phases induced by the combination of non-Hermiticity and disorders are dubbed non-Hermitian topological Anderson insulators. We also find that the system has non-monotonous localization behaviour and the topological transition is accompanied by an Anderson transition. These properties are general in other non-Hermitian models.