Observation of dynamical degeneracy splitting for the non-Hermitian skin effect

TL;DR

This paper experimentally observes the non-Hermitian skin effect and its relation to dynamical degeneracy splitting in a 2D acoustic crystal, providing new insights into non-Hermitian physics and a platform for further studies.

Contribution

It introduces an experimental platform to observe non-Hermitian skin effect and links it to dynamical degeneracy splitting through bulk band characterization.

Findings

Observation of non-Hermitian skin effect in acoustic crystal

Correlation between skin effect and dynamical degeneracy splitting

Validation of bulk band characterization method

Abstract

The non-Hermitian skin effect is a distinctive phenomenon in non-Hermitian systems, which manifests as the anomalous localization of bulk states at the boundary. To understand the physical origin of the non-Hermitian skin effect, a bulk band characterization based on the dynamical degeneracy on an equal frequency contour is proposed, which reflects the strong anisotropy of the spectral function. In this paper, we report the experimental observation of both phenomena in a two-dimensional acoustic crystal, and reveal their remarkable correspondence by performing single-frequency excitation measurements. Our work not only provides a controllable experimental platform for studying the non-Hermitian physics, but also confirms the correspondence between the non-Hermitian skin effect and the dynamical degeneracy splitting, paving a new way to characterize the non-Hermitian skin effect.