Unstable and stable regimes of polariton condensation

We experimentally investigate the spatiotemporal coherence properties of polariton condensates in GaAs-based microcavities under continuous-wave pumping. We demonstrate the existence of a dynamical instability of polariton condensates due to their coupling with the reservoir excitons. The turbulent behavior of this instability results in a strongly reduced spatial and temporal coherence and a significantly inhomogeneous density. We show how the instability can be tamed by introducing a periodic potential so that condensation occurs into negative mass states, leading to largely improved coherence and homogeneity. This method for suppressing instabilities paves the way to the exploration of long-range order in driven-dissipative systems with a controlled platform.