Gutzwiller study of phase diagrams of extended Bose—Hubbard models

Abstract

Hard-core and soft-core extended Bose-Hubbard models with fixed boson densities are studied by using the Gutzwiller variational wave function. The phase diagram of the softcore model strongly depends on its transfer integral. Specifically, a supersolid phase can be the ground state even below half-filling for a large transfer integral. The density difference between nearest-neighbor sites, which is an order parameter of the supersolid phase, strongly depends on the boson density, especially for a small transfer integral.