Exceptional Topology Survives Strong Hermitian Fields in Radiative Atomic Arrays
Abstract
Exceptional points are topological defects of complex band structures that are stable against weak perturbations, yet in two-band systems with bounded non-Hermitian couplings they are ultimately removed by a sufficiently strong Hermitian field. Here we demonstrate a striking exception in a two-dimensional subwavelength atomic array. Along a continuous square-to-triangular deformation at fixed magnetic field, the bulk passes between line-gapped topological regions with \textcolor{black}{band Chern numbers (C1,C2)=(2,−2)} through a gapless exceptional region. Within a finite interval of lattice deformation, increasing the magnetic field merely drives the exceptional points toward the light cone because of the singular radiative dipolar couplings. We further show that skin localization toward open boundaries responds non-monotonically to the same field. An intermediate field drives a bipolar skin localization, with bulk modes from different spectral branches accumulating at opposite boundaries, whereas stronger fields suppress boundary localization. Our results establish the interplay of lattice geometry, light-cone singularity, and Hermitian magnetic field as a route to engineering Chern and exceptional topology beyond the conventional strong-field limit.
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BibTeX
@misc{gou2026exceptional,
title = {{Exceptional Topology Survives Strong Hermitian Fields in Radiative Atomic Arrays}},
author = {Tian-Shu Gou and Yi-Cheng Wang and Ya-Tang Yu and Guin-Dar Lin and Jhih-Shih You and H. H. Jen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.17313},
eprint = {2609.17313},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17313},
}
RIS
TY - UNPB
TI - Exceptional Topology Survives Strong Hermitian Fields in Radiative Atomic Arrays
AU - Tian-Shu Gou
AU - Yi-Cheng Wang
AU - Ya-Tang Yu
AU - Guin-Dar Lin
AU - Jhih-Shih You
AU - H. H. Jen
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2609.17313
UR - https://arxiv.org/abs/2609.17313
AB - Exceptional points are topological defects of complex band structures that are stable against weak perturbations, yet in two-band systems with bounded non-Hermitian couplings they are ultimately removed by a sufficiently strong Hermitian field. Here we demonstrate a striking exception in a two-dimensional subwavelength atomic array. Along a continuous square-to-triangular deformation at fixed magnetic field, the bulk passes between line-gapped topological regions with \textcolor{black}{band Chern numbers (C_1,C_2)=(2,−2)} through a gapless exceptional region. Within a finite interval of lattice deformation, increasing the magnetic field merely drives the exceptional points toward the light cone because of the singular radiative dipolar couplings. We further show that skin localization toward open boundaries responds non-monotonically to the same field. An intermediate field drives a bipolar skin localization, with bulk modes from different spectral branches accumulating at opposite boundaries, whereas stronger fields suppress boundary localization. Our results establish the interplay of lattice geometry, light-cone singularity, and Hermitian magnetic field as a route to engineering Chern and exceptional topology beyond the conventional strong-field limit.
ER -