Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 18: Photon BEC

Q 18.7: Talk

Tuesday, March 3, 2026, 12:30–12:45, P 4

Steady-state behavior and symmetry breaking of photon BECs — •Milan Radonjić^1,2, Axel Pelster³, and Michael Thorwart¹ — ¹I. Institut für Theoretische Physik, Universität Hamburg, Germany — ²Institute of Physics Belgrade, University of Belgrade, Serbia — ³Physics Department, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, Germany

We revisit the dynamics of open, driven-dissipative photon Bose-Einstein condensates (phBECs) in a dye-filled microcavity using a cumulant expansion approach within the Lindblad formalism [1,2]. Motivated by a recent study [3], we extend our previous work [2] by considering, in addition to U(1)-invariant operator averages, the condensate amplitude and other U(1)-symmetry breaking amplitudes as non-zero. Specifically, we analyze the possible steady states of the dynamics using a method typically employed in laser theory. This allows us to critically examine the emergence of the ghost attractor and its impact on the long-time behavior of phBECs.
[1] P. Kirton and J. Keeling, Phys. Rev. Lett. 111, 100404 (2013).
[2] M. Radonjić et al., New J. Phys. 20, 055014 (2018).
[3] A. Abouelela et al., Phys. Rev. Lett. 135, 053402 (2025).

Keywords: Bose-Einstein condensate; Photon BEC; Cumulant expansion; Steady state; Dynamics