ANOMALOUS EFFECTS IN INTERACTING SPINLESS FERMION SYSTEMS WITH LOCAL DISORDER

Spinless fermions with local disorder and nearest neighbour repulsion are investigated on a Bethe lattice with infinite branching. Two phases are studied: a homogeneous phase and a checkerboard charge-density wave. Within this framework the model is exactly solved for all values of disorder, interaction and temperature. The transition between the two phases is described in detail. The density of states rho(omega), critical interaction U(c) and order parameter b are calculated. The system displays anomalous behaviour away from half-filling particle-density fluctuations due to weak disorder and/or low temperatures favour spontaneous symmetry breaking. We analyse and explain this unconventional phenomenon.