Stability and decay of subradiant patterns in a quantum gas with photon-mediated interactions.

Baumgärtner, Alexander; Hertlein, Simon; Schmit, Tom; Dreon, Davide; Máximo, Carlos; Li, Xiangliang; Morigi, Giovanna; Donner, Tobias · Sci Adv · 2025

basic_science · Level V

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Abstract

Metastability and its relaxation mechanisms challenge our understanding of the stability of quantum many-body systems, revealing a gap between the microscopic dynamics of the individual components and the effective descriptions used for macroscopic observables. We observe excited self-ordered subradiant patterns in a quantum gas coupled to two optical cavities and report lifetimes far beyond the system's typical timescales. These patterns eventually decay through an abrupt transition reordering the atoms into a superradiant phase. Ab initio theory fully captures this macroscopic behavior, revealing that the subradiant patterns are stabilized by photon-mediated long-range interactions, thereby manifesting universal features of metastability characteristic of long-range interacting systems, as in astrophysics and plasma physics. Our work sheds light on the microscopic mechanisms stabilizing quantum states of matter and highlights the potential of photon-mediated forces for engineering correlations in many-body quantum systems.