Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Phase Transitions

Q 27.4: Talk

Wednesday, March 13, 2024, 12:00–12:15, Aula

Transition between Directed Percolation and Mean Field Universality in a driven, dissipative Rydberg gas — •Simon Ohler, Daniel Brady, and Michael Fleischhauer — RPTU Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern

The spread of excitations in a laser driven gas of Rydberg atoms under facilitation conditions bears many similarities to epidemics. Increasing the drive strength, a non-equilibrium phase transition from an absorbing to an active phase occurs. We analyze the dynamics of the Rydberg many-body system in the facilitation regime close to the critical point as a function of the gas temperature by means of Monte-Carlo simulations. While at very low temperatures the phase transition belongs to the directed percolation universality class, the dynamical critical exponent crosses over into a mean field behavior with increasing temperature, reminiscent of anomalous directed percolation. Additionally, we consider the avalanche-like spread of excitation cascades. For all temperatures the system exhibits power-law distributed avalanche sizes, which are key signatures of self-organized criticality, a process believed to lie at the heart of many critical phenomena in nature.

Keywords: Rydberg; Criticality; Percolation; Universality; Facilitation