Construction and Observation of Flexibly Controllable High‐Dimensional Non‐Hermitian Skin Effects

Abstract

Non‐Hermitian skin effect (NHSE) is one of the most fundamental phenomena in non‐Hermitian physics. It is established that one‐dimensional NHSE originates from the nontrivial spectral winding topology. However, the topological origin behind the higher‐dimensional NHSE remains unclear, which poses a substantial challenge in constructing and manipulating high‐dimensional NHSEs. Here, an intuitive bottom‐to‐top scheme to construct high‐dimensional NHSEs is proposed, through assembling multiple independent one‐dimensional NHSEs. Not only the elusive high‐dimensional NHSEs can be effectively predicted from the well‐defined one‐dimensional spectral winding topologies, but also the high‐dimensional generalized Brillouin zones can be directly synthesized from the one‐dimensional counterparts. As examples, two two‐dimensional nonreciprocal acoustic metamaterials are experimentally implemented to demonstrate highly controllable multi‐polar NHSEs and hybrid skin‐topological effects, where the sound fields can be frequency‐selectively localized at any desired corners and boundaries. These results offer a practicable strategy for engineering high‐dimensional NHSEs, which could boost advanced applications such as selective filters and directional amplifiers.

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