Nodal phases in non-Hermitian wallpaper crystals

Symmetry and non-Hermiticity play pivotal roles in photonic lattices. While symmetries, such as parity-time ( P T) symmetry, have attracted ample attention, more intricate crystalline symmetries have been neglected in comparison. Here, we investigate the impact of the 17 wallpaper space groups of tw...

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Bibliographic Details
Published in:Applied physics letters 2024-01, Vol.124 (5)
Main Authors: König, J. Lukas K., Herber, Felix, Bergholtz, Emil J.
Format: Article
Language:English
Subjects:
Crystal lattices
fysik
lattice model
non-hermitian
photonic crystal
Photonic crystals
Physics
Symmetry
Wallpaper
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Summary:Symmetry and non-Hermiticity play pivotal roles in photonic lattices. While symmetries, such as parity-time ( P T) symmetry, have attracted ample attention, more intricate crystalline symmetries have been neglected in comparison. Here, we investigate the impact of the 17 wallpaper space groups of two-dimensional crystals on non-Hermitian band structures. We show that the non-trivial space group representations enforce degeneracies at high symmetry points and dictate their dispersion away from these points. In combination with either T or P T, the symmorphic p4 mm symmetry and the non-symmorphic p2mg, p2gg, and p4gm symmetries protect exceptional chains intersecting at the pertinent high symmetry points.
ISSN:0003-6951
1077-3118
1077-3118
DOI:10.1063/5.0185359