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Berlin 2024 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 28: Topology: Other Topics

TT 28.10: Vortrag

Dienstag, 19. März 2024, 12:00–12:15, H 3025

Symmetry-induced higher-order exceptional points in two dimensions — •Anton Montag1,2 and Flore Kunst11Max Planck Institute for the Science of Light, Erlangen, Germany — 2Departement of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Exceptional points (EPs) appear in non-Hermitian systems as points where the eigenvalues and eigenvectors coalesce. Even without any symmetries they are an abundant feature of non-Hermitian systems. In general, an EP of order n (EPn), where n eigenvectors coalesce, emerges if 2(n−1) real constraints are imposed. Symmetries that are local have been shown to reduce this number of constraints. In this work, we analyze higher-order EPs in two-dimensional parameter space induced by symmetries. We show that EP3s appear pairwise in the presence of any symmetry local in parameter space, and we illuminate the spectral structure around the EP3 pair. For each symmetry we show different general features that accompany the EP3s. Further we find EP4s and closely related EP5s induced by multiple symmetries. These EPs occur pairwise and have a complex spectral structure, which can be analyzed by analytically calculating the eigenvalues around those EP pairs.

Keywords: Non-hermitian topology; Exceptional points; Symmetry; Fermi arcs; Degenerate eigenvectors

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