Eric Roddick and David Stroud, Department of Physics, The Ohio State University, Columbus, OH, 43210

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 of these is a supersolid with coexisting long range phase coherence and checkerboard charge order. The supersolid phase is found to be robust even at half-integer 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 {\it et al} in comparable regions of parameter space, but differs in detail from that of a Bose-Hubbard model with nearest neighbor charging energies, probably because of differences in commutation relations.

PACS numbers: 74.20M, 74.50, 74.76, 05.30.J