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Asymmetric Elastic Bound State in the Continuum by an Exceptional Point
Liyun Cao1, Badreddine Assouar1
1Université de Lorraine, CNRS, IJL, F-54000 Nancy, France.
Physical Review Letters
|January 2, 2026
Summary
This study demonstrates an asymmetric elastic bound state in the continuum (BIC) using an exceptional point (EP). The system shows perfect energy localization for one incidence, enabling high-quality elastic-wave devices.
Area of Science:
- Acoustics and wave physics
- Non-Hermitian physics
- Elastic metamaterials
Background:
- Bound states in the continuum (BICs) offer perfect energy localization.
- Exceptional points (EPs) in non-Hermitian systems lead to unique phenomena.
- Asymmetric elastic systems are crucial for directional wave manipulation.
Purpose of the Study:
- To experimentally and theoretically demonstrate an asymmetric elastic BIC induced by an EP.
- To investigate the energy localization and quality factors (Q) of the induced quasi-BIC (qBIC).
- To explore the tunability of the qBIC and its evolution into a genuine BIC or EP BIC.
Main Methods:
- Fabrication and characterization of an open elastic system.
- Theoretical modeling using coupled-mode theory and finite element analysis.
- Experimental measurements of transmission spectra and linewidths.
Main Results:
- Observed vanishing linewidth for positive incidence, indicating BIC characteristics.
- Demonstrated perfect energy localization and high Q factors for the nontrivial qBIC in one direction.
- Showcased energy radiation and near-zero Q factors for the negative incidence.
- Confirmed the transition of qBIC to a genuine BIC by modulating system loss.
- Achieved an EP BIC with complete energy localization in a non-Hermitian resonator.
Conclusions:
- Established a novel connection between BICs and EPs in elastic systems.
- Revealed a physical mechanism for achieving asymmetric high Q and strong energy localization.
- Opened new avenues for designing high-performance elastic-wave devices with tailored properties.
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