# Reversal of the Skin Effect in Disordered Non-Hermitian Systems

## TL;DR

This paper explores how disorder can reverse the direction of a unique quantum phenomenon called the non-Hermitian skin effect in both one- and two-dimensional systems.

## Contribution

The study introduces a modified generalized Brillouin zone theory to predict and control the reversal of the non-Hermitian skin effect in disordered systems.

## Key findings

- Disorder exceeding a critical threshold reverses the direction of the non-Hermitian skin effect.
- The modified generalized Brillouin zone theory accurately predicts the reversal phenomenon.
- The effect's direction depends on disorder strength in each subsystem of two-dimensional quantum walks.

## Abstract

Non-Hermitian systems under nonreciprocity-induced evolution present an exotic phenomenon, known as the non-Hermitian skin effect. Yet, the control mechanisms and the generalized Brillouin zone in disordered systems have not been fully understood. Here, using Floquet quantum-walk models with disorder, we demonstrate effective control of the direction of the non-Hermitian skin effect in both one- and two-dimensional systems. Once the disorder strength exceeds a critical threshold, the direction of the skin effect is reversed. We develop a modified generalized Brillouin zone theory that correctly predicts skin effect reversal. Furthermore, we also investigate how the direction of the non-Hermitian skin effect depends on the disorder strength in each subsystem of the two-dimensional quantum walk. Our work paves the way for the design of quantum transport devices in quantum simulation platforms.