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Kardar-Parisi-Zhang universality in exciton-polariton condensates
Since the seminal paper by Kardar, Parisi and Zhang (KPZ) in 1986 on kinetic roughening of classical growing interfaces, the KPZ equation has arisen as a fundamental model in statistical physics for non-equilibrium scaling phenomena and phase transitions. Unexpectedly, it still unfolds new branching, such as a connection with the phase dynamics of open quantum systems displaying macroscopic spontaneous coherence.
In this talk, I will first give an overview of the realm of the KPZ equation. I will then focus on exciton-polaritons. These are hybrid quasi-particles emerging in semiconductor optical cavities from the strong coupling between electronic excitations in a quantum well and cavity photons. They behave collectively as a quantum fluid, featuring a Bose-Einstein condensation, which is genuinely out-of-equilibrium because of its driven-dissipative nature. I will explore the connection between the exciton-polariton condensate and the KPZ universality, and show that it extends well beyond the mere KPZ critical exponents. I will present results from both numerical simulations and a recent experiment.