Steady-state phases and tunneling-induced instabilities in the   driven-dissipative Bose-Hubbard model
  We determine the steady-state phases of a driven-dissipative Bose-Hubbard model, describing, e.g., an array of coherently pumped nonlinear cavities with a finite photon lifetime. Within a mean-field master equation approach using exact quantum solutions for the one-site problem, we show that the system exhibits a tunneling-induced transition between monostable and bistable phases. We characterize the corresponding quantum correlations, highlighting the essential differences with respect to the equilibrium case. We also find collective excitations with a flat energy-momentum dispersion over the entire Brillouin zone that trigger modulational instabilities at specific wavevectors. 
Alexandre Le Boit\'e (MPQ), Giuliano Orso (MPQ), Cristiano Ciuti (MPQ)
cond-mat.other quant-ph