Exploring dynamical phase transitions with a Cavity-QED platform

Atom-light interactions in optical cavities provide a platform for investigating many-body quantum physics in controlled environments. In particular, they have been proposed for the realization of collective quantum spin models with tunable long-range interactions. Besides the investigation of the rich steady-state phases that can arise due to the interplay between atom-light interactions and dissipation from the cavity, one opportunity offered by these systems is the study of out-of-equilibrium dynamical phases of matter  precluded from existence at equilibrium . Moreover, these phases can display intriguing universal behaviors akin to standard equilibrium phase transitions. Here, we report the observation of distinct dynamical phases of matter in a nearly unitary implementation of the collective XY spin model with transverse and longitudinal fields simulated via an ensemble of ∼106 88Sr atoms. The unique properties of our cavity-QED platform allow us to probe thedependence of the asso...