Phase stability in the two-dimensional anisotropic boson Hubbard Hamiltonian

The two-dimensional square lattice hard-core boson Hubbard model with near-neighbor interactions has a “checkerboard” charge density wave insulating phase at half filling and sufficiently large intersite repulsion. When doped, rather than forming a supersolid phase in which long-range charge density wave correlations coexist with a condensation of superfluid defects, the system instead phase separates. However, it is known that there are other lattice geometries and interaction patterns for which such coexistence takes place. In this paper we explore the possibility that anisotropic hopping or anisotropic near-neighbor repulsion might similarly stabilize the square lattice supersolid. By considering the charge density wave structure factor and superfluid density for different ratios of interaction strength and hybridization in the $\widehat{x}$ and $\widehat{y}$ directions, we conclude that phase separation still occurs.