Absorbing exceptional point of coherent vortex beams

Coherent perfect absorption at an exceptional point (CPA-EP) combines complete wave absorption with a non-Hermitian scattering degeneracy. Here, we realize CPA-EPs in chiral spaces using topological vortex beams and acoustic metasurfaces with tailored symmetry. We show that chiral CPA-EPs (CCPA-EPs) arise from the delicate interplay of mode channels encoding different topological charges (TCs), and TC channels supported by orbital angular momentum significantly boost the channel capacity of CCPA-EPs. Through rotational operations, the chiral system enables dynamic switching of absorption capacity and degenerate state transformation, where the introduced geometric phase amplifies the CCPA-EP response to significantly enhance sensitivity. We further demonstrate the coexistence of sensitivity (in EP state) and robustness (in CPA state) within the chiral space. Our findings broaden CPA-EP research and enable advanced devices on chiral wave systems. Absorbing exceptional points unite perfect absorption with wave degeneracy for versatile sound control. Here, authors establish acoustic vortex beams as topological channels for chiral absorbing exceptional points, enabling rotational switching, state conversion and expanded channel capacity.