Quasiperiodicity-induced non-Hermitian skin effect from the breakdown of scale-free localization

TL;DR

This paper explores how quasiperiodicity influences the non-Hermitian skin effect and scale-free localization in non-reciprocal systems, revealing a transition driven by boundary conditions and disorder.

Contribution

It uncovers the role of quasiperiodicity in causing the breakdown of scale-free localization and inducing the non-Hermitian skin effect in non-reciprocal lattices.

Findings

Quasiperiodicity induces a breakdown of scale-free localization.

Boundary conditions determine whether the system exhibits NHSE or extended states.

Quasiperiodicity plays a crucial role in non-Hermitian system behavior.

Abstract

Non-reciprocal systems exhibit extreme sensitivity to boundary conditions, typically manifesting as the non-Hermitian skin effect (NHSE) under open boundaries. By bridging the boundaries with a tunable impurity bond, one can access intermediate regimes where scale-free localization (SFL) can emerge. Here, we investigate the competition between such boundary coupling and quasiperiodic disorder in a non-reciprocal lattice. Our analyses reveal a quasiperiodicity-induced breakdown of the SFL regime, which evolves into either the NHSE or an extended regime, depending on boundary conditions. These results uncover the crucial role of quasiperiodicity in non-Hermitian systems.