VARIATIONAL MONTE-CARLO STUDY OF AN INTERACTING ELECTRON-PHONON MODEL

The phase diagram of a Hamiltonian with both on-site repulsion between electrons and with hopping probabilities which depend on dynamically varying separations of neighboring lattice sites has been studied with a new variational ansatz. A rich phase diagram is obtained as a funct ion of density, electron-electron, and electron-phonon interaction str engths. The superconducting regime is characterized by a pattern of sh ort and long bonds correlated with resonating pair hopping, whereas fo r the charge density wave phase this pattern is nearly static, and in the disordered and antiferromagnetic regimes all bond lengths are prac tically the same.