Transient non-Hermitian skin effect

Zhongming Gu; He Gao; Haoran Xue; Jensen Li; Zhongqing Su; Jie Zhu

doi:10.1038/s41467-022-35448-2

Transient non-Hermitian skin effect

Nat Commun. 2022 Dec 12;13(1):7668. doi: 10.1038/s41467-022-35448-2.

Authors

Zhongming Gu¹, He Gao², Haoran Xue³, Jensen Li⁴, Zhongqing Su⁵, Jie Zhu⁶

Affiliations

¹ Institute of Acoustics, School of Physics Science and Engineering, Tongji University, 200092, Shanghai, China.
² Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China. h.e.gao@connect.polyu.hk.
³ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore. haoran001@e.ntu.edu.sg.
⁴ Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.
⁵ Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
⁶ Institute of Acoustics, School of Physics Science and Engineering, Tongji University, 200092, Shanghai, China. jiezhu@tongji.edu.cn.

Abstract

The discovery of non-Hermitian skin effect (NHSE) has opened an exciting direction for unveiling unusual physics and phenomena in non-Hermitian system. Despite notable theoretical breakthroughs, actual observation of NHSE's whole evolvement, however, relies mainly on gain medium to provide amplified mode. It typically impedes the development of simple, robust system. Here, we show that a passive system is fully capable of supporting the observation of the complete evolution picture of NHSE, without the need of any gain medium. With a simple lattice model and acoustic ring resonators, we use complex-frequency excitation to create virtual gain effect, and experimentally demonstrate that exact NHSE can persist in a totally passive system during a quasi-stationary stage. This results in the transient NHSE: passive construction of NHSE in a short time window. Despite the general energy decay, the localization character of skin modes can still be clearly witnessed and successfully exploited. Our findings unveil the importance of excitation in realizing NHSE and paves the way towards studying the peculiar features of non-Hermitian physics with diverse passive platforms.