Phase transitions in dissipative Josephson chains : Monte Carlo results and response functions

A chain of Josephson junctions shunted by Ohmic resistors undergoes phase transitions at zero temperature that results from the interplay between quantum fluctuations induced by charging effects and the dissipation. The quantum-mechanical partition function expressed in terms of phase slips in space-time can be mapped onto that of a two-dimensional Coulomb gas. Due to the dissipation the interaction is anisotropic. Despite the simplicity of the model, there is no general agreement about the phase diagram and the response functions. The authors have performed Monte Carlo simulations to determine the zero-temperature phase boundaries. They find four phases with the absence or presence of global or local order, in all combinations. The authors discuss the response functions in the different phases and find interesting transport properties