Data from: A dissipation-induced superradiant transition in a strontium cavity-QED system

Driven-dissipative many-body systems are ubiquitous in nature and a
fundamental resource for quantum technologies. However, they are also
complex and hard to model since they cannot be described by the standard
tools in equilibrium statistical mechanics. Probing non-equilibrium
critical phenomena in pristine setups can illuminate new perspectives on
such systems. Here we use an ensemble of cold $^{88}$Sr atoms coupled to a
driven high-finesse cavity to study the cooperative resonance fluorescence
(CRF) model, a classic driven-dissipative model describing coherently
driven dipoles superradiantly emitting light. We observe its
non-equilibrium phase diagram characterized by a second-order phase
transition. Below a critical drive strength, the atoms quickly reach the
so-called superradiant steady-state featuring a macroscopic dipole moment;
above the critical point, the atoms undergo persistent Rabi-like
oscillations. At longer times, spontaneous emission transforms the
second-order transition into a discontinuous first-order transition. Our
observations pave the way for harnessing robust entangled states and
exploring boundary time crystals in driven-dissipative systems.