Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster I

HL 13.6: Poster

Monday, March 18, 2024, 15:00–18:00, Poster E

Manipulating spectral topology and exceptional points by nonlinearity in non-Hermitian polariton systems — Jan Wingenbach, Stefan Schumacher, and •Xuekai Ma — Physics Department and CeOPP, and PhoQS, Paderborn University, Germany

Exceptional points (EPs) are singularities in parameter space at which two or more eigenstates coalesce. Such singularities occur exclusively in non-Hermitian systems which are subject to gain and loss and exhibit non-orthogonal eigenvectors and complex eigenvalues. Due to their intriguing spectral topology EPs have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field [1]. We investigate the EPs in systems with significant nonlinearity, exemplified by a nonequilibrium exciton-polariton condensate. Polaritons are quasiparticles, formed due to the strong coupling of photons and excitons in planar semiconductor microcavities. With the possibility to control loss and gain and nonlinearity by optical means, this system allows for a comprehensive analysis of the interplay of nonlinearities (Kerr-type and saturable gain) and non-Hermiticity [2]. Not only do we find that EPs can be intentionally shifted in parameter space by the saturable gain, we also observe intriguing rotations and intersections of Riemann surfaces and find nonlinearity-enhanced sensing capabilities. These results illustrate the potential of tailoring spectral topology and related phenomena in non-Hermitian systems by nonlinearity. [1] J. Wiersig, et al., Photonics Research 8, 9 (2020). [2] J. Wingenbach, et al., arXiv:2305.04855 (2023).

Keywords: exceptional point; non-Hermitian; polariton; condensate; nonlinearity