Possibility of a metallic phase in granular superconducting films

We investigate the possibility of finding a zero-temperature metallic phase in granular superconducting films, modeled as a dissipative Bose system. We extend the conventional treatment of these systems to a formalism that can distinguish between insulator, metal, and superfluid phases. We do not find a metallic state at zero temperature. At finite temperatures, we find that the system exhibits a crossover between superfluid and metallic behavior. This has implications for the analysis of experimental results that makes use of a scaling hypothesis involving only a single parameter. We also investigate the effect of vortex dissipation in these systems.