LATTICE BOSON SYSTEMS WITH A FINITE MAXIMUM NUMBER OF BOSONS IN A SITE

We study a quantum spin-S Heisenberg Hamiltonian which can describe a system of bosons hopping over the sites of a lattice with intrasite re pulsion restricted to at most N=2S bosons in a site. The phase diagram displays a series of 2S-1 Mott-insulating lobes and a superfluid phas e. In the limit S-->infinity, the Hamiltonian reduces to the Bose-Hubb ard Hamiltonian with an infinite number of lobes. The case S=1, which possesses just one lobe, is studied in one dimension by the Lanczos me thod for chains of sizes up to 12 sites.