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arXiv · 2106.04582

Classification of Exceptional Nodal Topologies Protected by $\mathcal{PT}$ Symmetry

Marcus Stålhammar·Emil J. Bergholtz
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Abstract

Exceptional degeneracies, at which both eigenvalues and eigenvectors coalesce, and parity-time ($\mathcal{PT}$) symmetry, reflecting balanced gain and loss in photonic systems, are paramount concepts in non-Hermitian systems. We here complete the topological classification of exceptional nodal degeneracies protected by $\mathcal{PT}$ symmetry in up to three dimensions and provide simple example models whose exceptional nodal topologies include previously overlooked possibilities such as second-order knotted surfaces of arbitrary genus, third-order knots and fourth-order points.

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Marcus Stålhammar, Emil J. Bergholtz. 2021-06-08. Classification of Exceptional Nodal Topologies Protected by $\mathcal{PT}$ Symmetry. https://doi.org/10.1103/physrevb.104.l201104

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