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Non-Hermitian topological whispering gallery

Author

Listed:
  • Bolun Hu

    (Nanjing University)

  • Zhiwang Zhang

    (Nanjing University)

  • Haixiao Zhang

    (Nanjing University)

  • Liyang Zheng

    (Universidad Carlos III de Madrid)

  • Wei Xiong

    (Nanjing University)

  • Zichong Yue

    (Nanjing University)

  • Xiaoyu Wang

    (Nanjing University)

  • Jianyi Xu

    (Nanjing University)

  • Ying Cheng

    (Nanjing University)

  • Xiaojun Liu

    (Nanjing University)

  • Johan Christensen

    (Universidad Carlos III de Madrid)

Abstract

In 1878, Lord Rayleigh observed the highly celebrated phenomenon of sound waves that creep around the curved gallery of St Paul’s Cathedral in London1,2. These whispering-gallery waves scatter efficiently with little diffraction around an enclosure and have since found applications in ultrasonic fatigue and crack testing, and in the optical sensing of nanoparticles or molecules using silica microscale toroids. Recently, intense research efforts have focused on exploring non-Hermitian systems with cleverly matched gain and loss, facilitating unidirectional invisibility and exotic characteristics of exceptional points3,4. Likewise, the surge in physics using topological insulators comprising non-trivial symmetry-protected phases has laid the groundwork in reshaping highly unconventional avenues for robust and reflection-free guiding and steering of both sound and light5,6. Here we construct a topological gallery insulator using sonic crystals made of thermoplastic rods that are decorated with carbon nanotube films, which act as a sonic gain medium by virtue of electro-thermoacoustic coupling. By engineering specific non-Hermiticity textures to the activated rods, we are able to break the chiral symmetry of the whispering-gallery modes, which enables the out-coupling of topological ‘audio lasing’ modes with the desired handedness. We foresee that these findings will stimulate progress in non-destructive testing and acoustic sensing.

Suggested Citation

  • Bolun Hu & Zhiwang Zhang & Haixiao Zhang & Liyang Zheng & Wei Xiong & Zichong Yue & Xiaoyu Wang & Jianyi Xu & Ying Cheng & Xiaojun Liu & Johan Christensen, 2021. "Non-Hermitian topological whispering gallery," Nature, Nature, vol. 597(7878), pages 655-659, September.
  • Handle: RePEc:nat:nature:v:597:y:2021:i:7878:d:10.1038_s41586-021-03833-4
    DOI: 10.1038/s41586-021-03833-4
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    Cited by:

    1. Penghao Zhu & Xiao-Qi Sun & Taylor L. Hughes & Gaurav Bahl, 2023. "Higher rank chirality and non-Hermitian skin effect in a topolectrical circuit," Nature Communications, Nature, vol. 14(1), pages 1-7, December.
    2. Qiuyan Zhou & Jien Wu & Zhenhang Pu & Jiuyang Lu & Xueqin Huang & Weiyin Deng & Manzhu Ke & Zhengyou Liu, 2023. "Observation of geometry-dependent skin effect in non-Hermitian phononic crystals with exceptional points," Nature Communications, Nature, vol. 14(1), pages 1-8, December.
    3. Danwei Liao & Jingyi Zhang & Shuochen Wang & Zhiwang Zhang & Alberto Cortijo & María A. H. Vozmediano & Francisco Guinea & Ying Cheng & Xiaojun Liu & Johan Christensen, 2024. "Visualizing the topological pentagon states of a giant C540 metamaterial," Nature Communications, Nature, vol. 15(1), pages 1-7, December.
    4. Zhiwang Zhang & Penglin Gao & Wenjie Liu & Zichong Yue & Ying Cheng & Xiaojun Liu & Johan Christensen, 2022. "Structured sonic tube with carbon nanotube-like topological edge states," Nature Communications, Nature, vol. 13(1), pages 1-6, December.

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