Nonequilibrium phase transition in a radiation-driven Josephson junction

We predict that a nonequilibrium phase transition, analogous to optical bistability, occurs when coherent radiation is applied to an unbiased Josephson junction with an external resistance across it. The order parameter is the self-consistently developed dc voltage, and the drive parameter is the applied radiation intensity. The order parameter exhibits jump and hysteresis behavior characteristic of a first-order phase transition. The size of the hysteresis region can be tuned by varying the resistance. An approach based on the Fokker-Planck equation is adopted. The extremum of the stationary probability yields the self-consistency equation for the mean-field order parameter. Relaxation and decay times are calculated, the decay times being identified with the first passage time. Estimates of parameters show that the bistable regime could be experimentally accessible