Natural exceptional points in the excitation spectrum of a light-matter system

2023/06/02 by Opala, Andrzej, Furman, Magdalena, Król, Mateusz +7 · 4 citations
#FOS: Physical sciences #Optics (physics.optics) #Quantum Gases (cond-mat.quant-gas)

paper · doi:10.48550/arxiv.2306.01366

Abstract

We observe natural exceptional points in the excitation spectrum of an exciton-polariton system by optically tuning the light-matter interactions. The observed exceptional points do not require any spatial or polarization degrees of freedom and result solely from the transition from weak to strong light-matter coupling. We demonstrate that they do not coincide with the threshold for photon lasing, confirming previous theoretical predictions [Phys. Rev. Lett. 122, 185301 (2019), Optica 7, 1015 (2020) ]. Using a technique where a strong coherent laser pump induces up-converted excitations, we encircle the exceptional point in the parameter space of coupling strength and particle momentum. Our method of local optical control of light-matter coupling paves the way to investigation of fundamental phenomena including dissipative phase transitions and non-Hermitian topological states.

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