Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 24: Poster II

Q 24.45: Poster

Tuesday, March 12, 2024, 17:00–19:00, KG I Foyer

Critical exponents of a non-equilibrium phase transition in a facilitated Rydberg gas — •Daniel Brady, Simon Ohler, and Michael Fleischhauer — RPTU Kaiserslautern

We study a gas of driven Rydberg atoms, where excitations can spread through facilitation, comparable to the spread of an infectious disease. Importantly, the system shows a non-equilibrium dynamical phase transition from an active to an absorbing state, depending on driving and density. This transition is characterized by two critical exponents, which we investigate numerically close to the critical point as a function of the gas temperature. For the case of very low temperatures, we find a directed percolation-type transition due to the effects of Rydberg blockade, whereas for increasing temperatures we find a crossover to a mean-field transition. We also study the fast *avalanches* of excitations at the critical point and find they are power-law distributed with an exponent that is independent of temperature and comparable to many other systems known under the term self-organized criticality.

Keywords: Self-Organized Criticality; Griffiths Phase; Rydberg Atoms; Non-equilibrium Phase Transitions; Ultracold Gases