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Q: Fachverband Quantenoptik und Photonik
Q 11: QED and Cavity QED
Q 11.2: Talk
Monday, March 10, 2025, 17:15–17:30, HS Botanik
Re-entrant phase transition in many-body Cavity QED — •Tom Schmit1, Tobias Donner2, and Giovanna Morigi1 — 1Theoretische Physik, Universität des Saarlandes, 66123 Saarbrücken, Germany — 2Institute for Quantum Electronics, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
We analyse theoretically self-organization of atoms that couple dispersively to an optical cavity and are subject to a transverse pump, in a configuration experimentally studied[1]. The transverse pump laser is blue-detuned w.r.t. the atomic transition, confining the atoms in the intensity minima of the generated optical lattice. The competition of pump and cavity field leads to self-organization of the atoms in an ordered pattern, giving rise to a re-entrant phase transition, such that by increasing the pump intensity above a critical value, one first observes a transition from disorder to self-organized and then, at larger values, again back to a disordered phase[1]. Our theoretical model, founded on a mean-field ansatz, provides a description of the stationary state’s phase diagram in relation to pump intensity and detuning from the cavity frequency, aligning well with experimental observations. We show that stability of the ordered pattern is warranted when the scattered light interferes destructively with the pump at the atomic positions, effectively keeping the atoms in darkness. We discuss the connection between this phenomenon and inverse melting, observed in (classical) systems with repulsive and competing long-range interactions.
[1] P. Zupancic, et al., Phys. Rev. Lett. 123, 233601 (2019).
Keywords: Cavity QED; Self-organization; Re-entrant phase transition; Inverse melting; Long-range interaction