Topological Classificaton of Non-Hermitian Gapless Phases: Exceptional Points and Bulk Fermi Arcs

Abstract

We provide classification of gapless phases in non-Hermitian systems according to two types of complex-energy gaps: point gap and line gap. We show that exceptional points, at which not only eigenenergies but also eigenstates coalesce, are characterized by gap closing of point gaps with nontrivial topological charges. Moreover, we find that bulk Fermi arcs accompanying exceptional points are robust because of topological charges for real line gaps. On the basis of the classification, some examples are also discussed.

arXiv comment6 pages, 1 figure, 3 tables, submitted to the Proceedings of SCES 2019

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• The Bulk-boundary Correspondence in Non-Hermitian Hopf-link Exceptional Line Semimetals
• Two-dimensional anisotropic non-Hermitian Lieb lattice
• Unconventional steady states and topological phases in an open two-level non-Hermitian system
• Non-Hermitian Josephson junctions with four Majorana zero modes