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 9.4: Hauptvortrag

Montag, 5. September 2022, 16:45–17:15, H33

Nonlinear dynamics and exceptional points in exciton-polariton condensates — •Stefan Schumacher — Physics Department & CeOPP, Paderborn University, Germany

Non-Hermitian physics and exceptional points have attracted significant attention in the past two decades. Enormous progress has been made for example in non-Hermitian optics. Non-Hermitian degeneracies and exceptional points have also been demonstrated for exciton polaritons in semiconductor microcavities [1]. For non-resonant excitation, polaritons can spontaneously exhibit macroscopic coherence, known as polariton condensation. The non-equilibrium nature of polariton condensates makes them perfect for studies of non-Hermitian physics. The gain can be tailored by varying the spatial optical pump profile, for example allowing realization of PT-symmetric lattices [2]. The polariton-polariton interaction gives rise to inherently nonlinear phenomena such as vortex formation [3]. Recently, we reported the observation of an exceptional point in a double-well potential [4]. There, the polariton condensate can be localized in one well and switched off by an additional optical excitation in the other well that surprisingly induces additional loss [4]. The nonlinearity and related energy blueshift also allows to approach the exceptional point. This work paves the way to explore non-Hermitian physics in a system with strong nonlinearity and in tailored potential energy landscapes. [1] T. Gao et al., Nature 526, 554-558 (2015). [2] X. Ma et al., New Journal of Physics 21, 123008 (2019). [3] X. Ma et al., Nature Communications 11, 897 (2020). [4] Y. Li et al., arXiv:2101.09478 (2021).