Supersolid phase in fully frustrated Josephson-junction arrays

We study the phase diagram and the excitation spectra of an array of small Josephson junctions at f = 1/2 and arbitrary charge frustration. We find that the supersolid region in the phase diagram is larger than the corresponding region at f = 0 and it includes two different phases. In the chiral supersolid charges and vortices are arranged in a checkerboard pattern on a 2 x 2 supercell analogously to the unfrustrated case. We find a phase, which we term nonchiral supersolid, which has no corresponding phase at f = 0. The excitation spectra in the supersolid regions show particlelike dispersion which is related to the existence of defectons. The defecton condensation leads to superfluidity in the presence of a charge-ordered background.