Mainz 2026 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 28: Poster – Quantum Optics
Q 28.12: Poster
Dienstag, 3. März 2026, 17:00–19:00, Philo 2. OG
Re-entrant phase transition in many-body Cavity QED — •Tom Schmit1, Laura Batini2, Justyna Stefaniak3, David Baur3, Gabriele Natale3, Fabian Bennati Weis3, Nicolò Defenu2, Tobias Donner3, and Giovanna Morigi1 — 1Theoretische Physik, Universität des Saarlandes, 66123 Saarbrücken, Germany — 2Institut für Theoretische Physik, Eidgenössische Technische Hochschule Zürich, Wolfgang-Pauli-Straße 27, 8093 Zürich, Switzerland — 3Institute for Quantum Electronics, Eidgenössische Technische Hochschule Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
A driven quantum gas of atoms in an optical cavity offers a powerful platform for exploring the equilibrium properties of long-range interacting systems. The interplay between the external drive, quantum fluctuations, and the cavity-mediated long-range interaction can lead to the formation of stable self-organized structures. When the system is transversaly driven with a laser that is blue-detuned from the atomic transition, an intriguing behaviour is observed: as the drive strength increases, the system first undergoes a transition from the normal phase to a self-organized phase at a critical threshold, but then, at a higher threshold, exhibits a re-entrant phase transition back to the normal phase, as experimentally demonstrated[1]. In this work, we develop a Ginzburg-Landau model for the transition between the normal and self-organized phases, based on a mean-field ansatz. This framework allows us to identify the mechanisms that stabilize and destabilize the self-organized state, giving the re-entrant behaviour.
Keywords: Cavity QED; Self-organization; Re-entrant phase transition; Long-range interaction; Competiting orders