Zhang Li, Yang Yihao, Ge Yong, Guan Yi-Jun, Chen Qiaolu, Yan Qinghui, Chen Fujia, Xi Rui, Li Yuanzhen, Jia Ding, Yuan Shou-Qi, Sun Hong-Xiang, Chen Hongsheng, Zhang Baile
Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, 310027, China.
ZJU-Hangzhou Global Science and Technology Innovation Center, Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, ZJU-UIUC Institute, Zhejiang University, Hangzhou, 310027, China.
Nat Commun. 2021 Nov 2;12(1):6297. doi: 10.1038/s41467-021-26619-8.
The recently discovered non-Hermitian skin effect (NHSE) manifests the breakdown of current classification of topological phases in energy-nonconservative systems, and necessitates the introduction of non-Hermitian band topology. So far, all NHSE observations are based on one type of non-Hermitian band topology, in which the complex energy spectrum winds along a closed loop. As recently characterized along a synthetic dimension on a photonic platform, non-Hermitian band topology can exhibit almost arbitrary windings in momentum space, but their actual phenomena in real physical systems remain unclear. Here, we report the experimental realization of NHSE in a one-dimensional (1D) non-reciprocal acoustic crystal. With direct acoustic measurement, we demonstrate that a twisted winding, whose topology consists of two oppositely oriented loops in contact rather than a single loop, will dramatically change the NHSE, following previous predictions of unique features such as the bipolar localization and the Bloch point for a Bloch-wave-like extended state. This work reveals previously unnoticed features of NHSE, and provides the observation of physical phenomena originating from complex non-Hermitian winding topology.
最近发现的非厄米趋肤效应（NHSE）表明能量非保守系统中拓扑相的当前分类已失效，并且需要引入非厄米能带拓扑。到目前为止，所有NHSE观测都是基于一种非厄米能带拓扑，其中复能谱沿着一个闭环缠绕。正如最近在光子平台上沿着一个合成维度所表征的那样，非厄米能带拓扑在动量空间中可以表现出几乎任意的缠绕，但它们在实际物理系统中的实际现象仍不清楚。在这里，我们报告了在一维（1D）非互易声晶体中NHSE的实验实现。通过直接声学测量，我们证明了一种扭曲缠绕，其拓扑结构由两个相互接触的相反取向的环组成，而不是单个环，这将显著改变NHSE，这与之前关于双极局域化和类布洛赫波扩展态的布洛赫点等独特特征的预测一致。这项工作揭示了NHSE以前未被注意到的特征，并提供了对源自复杂非厄米缠绕拓扑的物理现象的观测。
