Regensburg 2022 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 9: Focus Session: Exceptional Points and Non-Hermitian Physics in Semiconductor Systems

HL 9.5: Vortrag

Montag, 5. September 2022, 17:15–17:30, H33

Exceptional points in anisotropic ZnO thin films — •Sebastian Henn, Evgeny Krüger, Chris Sturm, and Marius Grundmann — 1 Universität Leipzig, Faculty of Physics and Earth Sciences, Felix Bloch Institute for Solid State Physics, Linnéstr. 5, 04103 Leipzig, Germany

In this talk we present findings regarding the existence of exceptional points in anisotropic thin films. Analogous to degeneracies of optic axes in absorptive biaxial materials, so-called singular optic axes [1], anisotropic transparent structures contain exceptional points in momentum space, where two orientation- and polarization-dependent modes are equal in resonance energy and lifetime. The latter is determined by dissipative photon loss at the interfaces, which renders the system non-Hermitian. This phenomenon has been observed in dielectric optical microcavities [2] and principally exists also in anisotropic thin films, where resonances correspond to well-known Fabry-Pérot modes. We show results of rigorous calculations for m-ZnO thin films, based on scattering matrices whose complex poles correspond to the resonance energies. This allows to find exceptional points in two-dimensional momentum space and we confirm important characteristics, such as a square-root topology and circularity.

[1] Grundmann et al., Phys. Status Solidi RRL 11.1 1600295 (2017)

[2] S. Richter et al., Phys. Rev. Lett. 123 227401 (2019)