Emergent thermal fluctuations and non-Hermitian phase transitions in open photon condensates

Moritz Janning; Roman Kramer; Michael Turaev; Sayak Ray; Johann Kroha

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arXiv · 2603.21927

Emergent thermal fluctuations and non-Hermitian phase transitions in open photon condensates

Moritz Janning·Roman Kramer·Michael Turaev·Sayak Ray·Johann Kroha

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Abstract

We investigate the nonequilibrium dynamics of an open photon Bose-Einstein condensate in a dye-filled microcavity using a Lindblad master-equation approach, treating the condensate and the noncondensed fluctuations on the same footing. The driven-dissipative condensate exhibits a long-lived, metastable plateau stabilized by a ghost attractor, a fixed point that lies outside the physical domain in configuration space, yet stalls the condensate dynamics for exceedingly long times before it dephases to zero [Phys. Rev. Lett. 135, 053402 (2025)]. Despite the nonequilibrium origin of this dynamical stabilization, the condensate exhibits quasithermal fluctuations in the plateau in that the relative order-parameter fluctuations scale as the inverse square root of the system size. A linear stability analysis further reveals the presence of exceptional points, resulting in multiple non-Hermitian phase transitions associated with the relaxation dynamics into and out of the metastable condensate.

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Moritz Janning, Roman Kramer, Michael Turaev, Sayak Ray, Johann Kroha. 2026-03-23. Emergent thermal fluctuations and non-Hermitian phase transitions in open photon condensates. https://arxiv.org/abs/2603.21927

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