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Projected Coherent Perfect Absorption at Exceptional Points via Nonlocal Elastodynamic Coupling

Jingyi Chen1,*, Di Wang2,*, Jiacheng Xing1, Xu Wang1,†, and Jie Zhu1,2,‡

  • 1Institute of Acoustics, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
  • 2Shanghai Research Institute for Intelligent Autonomous Systems, Tongji University, Shanghai 201210, China

  • *These authors contributed equally to this work.
  • †Contact author: xuwang@tongji.edu.cn
  • ‡Contact author: jiezhu@tongji.edu.cn
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Phys. Rev. Lett. 137, 186601 – Published 28 October, 2026

DOI: https://doi.org/10.1103/87nl-4ypz

Abstract

In non-Hermitian physics, coherent perfect absorption at an exceptional point (CPA EP) emerges as a unique degenerate state that can manifest anomalously broadened absorption line shape implying strong robustness, which apparently contradicts the extreme sensitivity rooted in EPs. To investigate this unique state, we design an underwater acoustic metasurface comprising a beam splitter and a retroreflector on opposite sides. We leverage fluid-solid interaction (FSI) as a powerful mechanism to engineer the non-Hermitian coupling, circumventing the necessity for difficult-to-tune gain or loss for the degeneracy. FSI-induced strong nonlocal elastodynamic coupling concurrently morphs the previously independent spatial subspaces, creating contrasting non-Hermitian behaviors in the respective subspaces, with one encoding the projected CPA EP. We prove that the CPA EP inherits core attributes from both states, manifesting the coexistence of macroscopic operational robustness (from CPA) and microscopic topological hypersensitivity (from EP). We further experimentally demonstrate that the CPA EP, in turn, acts as a knob to modulate the FSI coupling channel, allowing its full activation (for perfect anomalous deflection) or, by leveraging the missing dimension, complete suppression (for total reflection). This synergy between FSI and non-Hermitian degeneracies shows potential for multifunctional hydroacoustic devices.

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Outline

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Phys. Rev. Lett. 137, 186601– Published 28 October, 2026
  • Received 27 June 2026
  • Revised 11 September 2026
  • Accepted 6 October 2026
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