biostudies-literatureWang YCMinistry of Science and Technology, TaiwanMinistry of Science and Technology, Taiwan (Ministry of Science and Technology of Taiwan)4598https://www.ebi.ac.uk/biostudies/studies/S-EPMC9357005biostudies-literatureUnknown13(1)Explorations of symmetry and topology have led to important breakthroughs in quantum optics, but much richer behaviors arise from the non-Hermitian nature of light-matter interactions. A high-reflectivity, non-Hermitian optical mirror can be realized by a two-dimensional subwavelength array of neutral atoms near the cooperative resonance associated with the collective dipole modes. Here we show that exceptional points develop from a nondefective degeneracy by lowering the crystal symmetry of a square atomic lattice, and dispersive bulk Fermi arcs that originate from exceptional points are truncated by the light cone. From its nontrivial energy spectra topology, we demonstrate that the geometry-dependent non-Hermitian skin effect emerges in a ribbon geometry. Furthermore, skin modes localizNature communicationsA non-Hermitian optical atomic mirror.PMC9357005MOST-110-2112-M-003-008-MY3MOST-109-2112-M-001-035-MY3Jen HHWang YCYou JSfalseA non-Hermitian optical atomic mirror.Explorations of symmetry and topology have led to important breakthroughs in quantum optics, but much richer behaviors arise from the non-Hermitian nature of light-matter interactions. A high-reflectivity, non-Hermitian optical mirror can be realized by a two-dimensional subwavelength array of neutral atoms near the cooperative resonance associated with the collective dipole modes. Here we show that exceptional points develop from a nondefective degeneracy by lowering the crystal symmetry of a square atomic lattice, and dispersive bulk Fermi arcs that originate from exceptional points are truncated by the light cone. From its nontrivial energy spectra topology, we demonstrate that the geometry-dependent non-Hermitian skin effect emerges in a ribbon geometry. Furthermore, skin modes localiz2022-01-01T00:00:00Z2022 Aug2025-04-18T15:26:05.864Z2025-02-19T02:27:12.313ZS-EPMC93570053593351410.1038/s41467-022-32372-3