Non-Hermitian acoustic metamaterials: Role of exceptional points in sound absorption

摘要

Effective non-Hermitian Hamiltonians are obtained to describe coherent perfect absorbing and lasing boundaryconditions. PT symmetry of the Hamiltonians enables us to design configurations which perfectly absorb atmultiple frequencies. Broadened and flat perfect absorption is predicted at the exceptional point of PT -symmetrybreaking while, for a particular case, absorption is enhanced with the use of gain. The aforementioned phenomenaare illustrated for acoustic scattering through Helmholtz resonators revealing how tailoring the non-Hermiticityof acoustic metamaterials leads to novel mechanisms for enhanced absorption.