Bose–Fermi–Hubbard model: Pseudospin operator approach

The thermodynamics of the Bose–Fermi–Hubbard model with direct interaction between neighbour bosonic particles is considered in this work at finite temperature. The hard-core boson case is considered and the pseudospin formalism is used. Charge susceptibility of the system is calculated and the possibilities of the transitions to the charge density wave order, superfluid and supersolid phases are analysed. We derive an analytic formula for the grand canonical potential and analyse the thermodynamically stable states.