Stochastic transitions between phase-locked steady states in RF-irradiated graphene Josephson junctions*

We investigate the Shapiro steps in a graphene-based Josephson junction with large gap MoRe leads. A wide variety of patterns are obtained, depending on the carrier density, temperature, RF frequency, and magnetic field. A particularly interesting regime of intermediate driving power is identified, in which the zero voltage state becomes unstable even at zero bias, and the junction spontaneously develops a voltage V=±~hf/2e, which could persist for a several hours. We study the switching time between the ±~hf/2e states as a function of applied power and temperature, and find a novel non-monotonic regime, in which the switching time between these attractors demonstrates a pronounced minimum at intermediate temperatures.