INCOMMENSURATE PHASES VS PHASE-SEPARATION FOR INTERACTING SPINLESS FERMIONS

The phase diagram of interacting spinless fermions on a hypercubic lat tice is investigated by means of the limit of infinite dimensions. In this limit the susceptibility chi can be calculated explicitly for any value of the wave vector k in the homogeneous phase and in the charge -density wave phase (CDW) with Q = (pi, pi, ...pi) (chessboard). At ze ro temperature we find that only the homogeneous phase or, at half-fil ling, the CDW is stable; for intermediate fillings phase separation oc curs. At finite temperatures a divergence of CHI for incommensurate wa ve vectors appears in a certain parameter region and the CDW is stabil ized around half-filling. Our results suggest the possibility of a sim ilar scenario in the Hubbard model.