Non-Hermitian route to higher-order topology in an acoustic crystal

He Gao, Haoran Xue, Zhongming Gu, Tuo Liu, Jie Zhu, Baile Zhang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Topological phases of matter are classified based on their Hermitian Hamiltonians, whose real-valued dispersions together with orthogonal eigenstates form nontrivial topology. In the recently discovered higher-order topological insulators (TIs), the bulk topology can even exhibit hierarchical features, leading to topological corner states, as demonstrated in many photonic and acoustic artificial materials. Naturally, the intrinsic loss in these artificial materials has been omitted in the topology definition, due to its non-Hermitian nature; in practice, the presence of loss is generally considered harmful to the topological corner states. Here, we report the experimental realization of a higher-order TI in an acoustic crystal, whose nontrivial topology is induced by deliberately introduced losses. With local acoustic measurements, we identify a topological bulk bandgap that is populated with gapped edge states and in-gap corner states, as the hallmark signatures of hierarchical higher-order topology. Our work establishes the non-Hermitian route to higher-order topology, and paves the way to exploring various exotic non-Hermiticity-induced topological phases.

Original languageEnglish
Article number1888
JournalNature Communications
Volume12
Issue number1
DOIs
Publication statusPublished - 25 Mar 2021

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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