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arXiv · 2411.06898

Exceptional second-order topological insulators

Yutaro Tanaka·Daichi Nakamura·Ryo Okugawa·Kohei Kawabata
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Abstract

Point-gap topological phases of non-Hermitian systems exhibit exotic boundary states that have no counterparts in Hermitian systems. Here, we develop classification of second-order point-gap topological phases protected by reflection symmetry. Based on this classification, we propose exceptional second-order topological insulators, exhibiting second-order boundary states stabilized by point-gap topology. As an illustrative example, we uncover a two-dimensional exceptional second-order topological insulator with point-gapless corner states. Furthermore, we identify a three-dimensional exceptional second-order topological insulator that features hinge states with isolated exceptional points, representing second-order topological phases intrinsic to non-Hermitian systems. Our work enlarges the family of point-gap topological phases in non-Hermitian systems.

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Yutaro Tanaka, Daichi Nakamura, Ryo Okugawa, Kohei Kawabata. 2024-11-11. Exceptional second-order topological insulators. https://doi.org/10.1103/6dhc-34vj

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