Symmetry-induced higher-order exceptional points in two dimensions

• DOI: 10.48550/arxiv.2401.10913
• Publication Date: 2024-01-01
• Authors: Anton Montag; Flore K. Kunst
• Keywords: Local symmetry

Exceptional points of order $n$ (EP$n$s) appear in non-Hermitian systems as where the eigenvalues and eigenvectors coalesce. Whereas EP2s generically two dimensions (2D), higher-order EPs require a higher-dimensional parameter space to emerge. In this work, we provide complete characterization appearance symmetry-induced 2D space. We find that besides only EP3s, EP4s, EP5s can be stabilized 2D. Moreover, these must always pairs with their dispersion determined by symmetries. Upon studying complex spectral structure around EPs, depending on symmetry, EP3s are accompanied EP2 arcs, 2- 3-level open Fermi structures. Similarly, EP4s closely related EP5s, which arise due multiple symmetries, exotic EP arcs For each case, an explicit example. also comment topological charge discuss similarities differences between symmetry-protected EP2s.