INCOMMENSURATE PHASES VS PHASE-SEPARATION FOR INTERACTING SPINLESS FERMIONS

The phase diagram of interacting spinless fermions on a hypercubic lattice 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 zero temperature we find that only the homogeneous phase or, at half-filling, the CDW is stable; for intermediate fillings phase separation occurs. At finite temperatures a divergence of CHI for incommensurate wave vectors appears in a certain parameter region and the CDW is stabilized around half-filling. Our results suggest the possibility of a similar scenario in the Hubbard model.