Two supersolid phases in hard-core extended Bose–Hubbard model

The effect of the next-nearest-neighbor (nnn) tunneling on the hard-core extended Bose–Hubbard model on square lattices is investigated. By means of the cluster mean-field theory, the ground-state phase diagrams are determined. When a modest nnn tunneling is introduced, depending on its sign, two distinct supersolid (SS) states with checkerboard crystal structures are found away from half-filing. The characters of various phase transitions out of these two SS states are discussed. In particular, for the case with kinetic frustration, the existence of a half SS phase possessing both solid and unconventional superfluid orders is established. Our work hence sheds light on the search of this interesting SS phase in real ultracold lattice gases with frustrated tunnelings.