Dislocation Non-Hermitian Skin Effect

TL;DR

This paper reveals how crystal defects can serve as probes for non-Hermitian topological phases, showing that dislocations induce localized states and skin effects in various non-Hermitian systems, including gapless ones with exceptional points.

Contribution

It introduces the concept of dislocation-induced non-Hermitian skin effects and relates them to bulk topology in both gapped and gapless non-Hermitian systems.

Findings

Dislocations can induce skin effects in non-Hermitian systems.

Strong point-gap topology can cause dislocation responses without skin effects.

Gapless systems with exceptional points exhibit localized dislocation responses.

Abstract

We demonstrate that crystal defects can act as a probe of intrinsic non-Hermitian topology. In particular, in point-gapped systems with periodic boundary conditions, a pair of dislocations may induce a non-Hermitian skin effect, where an extensive number of Hamiltonian eigenstates localize at only one of the two dislocations. An example of such a phase are two-dimensional systems exhibiting weak non-Hermitian topology, which are adiabatically related to a decoupled stack of Hatano-Nelson chains. Moreover, we show that strong two-dimensional point-gap topology may also result in a dislocation response, even when there is no skin effect present with open boundary conditions. For both cases, we directly relate their bulk topology to a stable dislocation non-Hermitian skin effect. Finally, and in stark contrast to the Hermitian case, we find that gapless non-Hermitian systems hosting bulk exceptional points also give rise to a well-localized dislocation response.