Phase diagram of dissipative two-dimensional Josephson junction arrays

A variety of condensed-matter systems with an intermediate (mesoscopic) scale have been recently developed. The characteristic quantum effects involving a macroscopic number of particles cause peculiar properties of all such devices, which make them appealing for applications. However the sizeable dimension of the devices implies that the relevant dynamical variables have to be considered as coupled to a very large (infinite) number of degrees of freedom of the surrounding environment (or dissipation bath). In these open systems, interaction with the environment leads in general to dissipation and decoherence which strongly affect the behavior of the system. It is thus essential to study both quantum and dissipative effects. Two-dimensional (2D) arrays of nanosized Josephson junctions, both unshunted and shunted can indeed be produced, giving the opportunity to experimentally test the effects of dissipation.