OFF-DIAGONAL LONG-RANGE ORDER IN GENERALIZED HUBBARD MODELS

We present stochastic diagonalization results for the ground-state ene rgy and the largest eigenvalue of the two-fermion density matrix of th e BCS reduced Hamiltonian, the Hubbard model, and the Hubbard model wi th correlated hopping. The system-size dependence of this eigenvalue i s used to study the existence of Off-Diagonal Long-Range Order in thes e models. We show that the model with correlated hopping and repulsive on-site interaction can exhibit Off-Diagonal Long-Range Order. Analyt ical results for some special limiting cases indicate that Off-Diagona l Long-Range Order not always implies superconductivity.