Emerging dissipative phases in a superradiant quantum gas with tunable decay

Abstract: Exposing a many-body system to external drives and losses can transform the nature of its phases and opens perspectives for engineering new properties of matter. How such characteristics are related to the underlying microscopic processes of the driven and dissipative system is a fundamental question. Here we address this point in a quantum gas that is strongly coupled to a lossy optical cavity mode using two independent Raman drives, which act on the spin and motional degrees of freedom of the atoms. This setting allows us to control the competition between coherent dynamics and dissipation by adjusting the imbalance between the drives. For strong enough coupling, the transition to a superradiant phase occurs, as is the case for a closed system. Yet, by imbalancing the drives we can enter a dissipation-stabilized normal phase and a region of multistability. Measuring the properties of excitations on top of the out-of-equilibrium phases reveals the microscopic elementary processes in the open system. Our findings provide prospects for studying squeezing in non-Hermitian systems, quantum jumps in superradiance, and dynamical spin-orbit coupling in a dissipative setting.