Supersolid phases in underdamped Josephson arrays: Quantum Monte Carlo simulations

We carry out a quantum Monte Carlo study of Josephson arrays at temperature T=0 in the presence of an offset voltage between array and substrate. With diagonal and nearest-neighbor charge coupling, we find two types of insulating lobes with different types of charge order, and two types of superconducting regions. One is a supersolid with coexisting long-range phase coherence and checkerboard charge order. The supersolid phase is robust at half-filling. With next-nearest-neighbor coupling, there are two types of supersolid phase, one with checkerboard and one with striped charge order. Our phase diagram agrees with mean-field theory and with quantum Monte Carlo results of van Otterlo et al. in comparable regions of parameter space, but differs in detail from that of a Bose-Hubbard model with nearest-neighbor charging energies