Spectral Riemann sheet topology of gapped non-Hermitian systems

Montag A, Felski A, Kunst FK (2026)

Publication Type: Journal article

Publication year: 2026

Journal

SciPost Physics SciPost

Book Volume: 20

Article Number: 133

Journal Issue: 5

DOI: 10.21468/SciPostPhys.20.5.133

Abstract

We show topological configurations of the complex-valued spectra in gapped non-Hermitian systems. These arise when the distinctive EPs in the energy Riemann sheets of such models are annihilated after threading them across the boundary of the Brillouin zone. This results in a non-trivially closed branch cut that is protected by an energy gap in the spectrum. Their presence or absence establishes topologically distinct configurations for fully non-degenerate systems and tuning between them requires a closing of the gap, forming exceptional point degeneracies. We provide an outlook toward experimental realizations in metasurfaces and single-photon interferometry.

Involved external institutions

Max-Planck-Institut für die Physik des Lichts (MPL) / Max Planck Institute for the Science of Light DE Germany (DE)

How to cite

APA:

Montag, A., Felski, A., & Kunst, F.K. (2026). Spectral Riemann sheet topology of gapped non-Hermitian systems. SciPost Physics, 20(5). https://doi.org/10.21468/SciPostPhys.20.5.133

MLA:

Montag, Anton, Alexander Felski, and Flore K. Kunst. "Spectral Riemann sheet topology of gapped non-Hermitian systems." SciPost Physics 20.5 (2026).

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