LONG-RANGE ELECTRON-PHONON CORRELATION AND PEIERLS DIMERIZATION IN THE ONE-DIMENSIONAL MOLECULAR-CRYSTAL MODEL

In this paper, we reexamine the effect of quantum lattice fluctuations in a half-filled quasi-one-dimensional electron-phonon coupling syste m by considering long-range electron-phonon correlation more precisely . Our results coincide with previous papers in the omega = 0 (adiabati c) and omega = infinity cases. We note that the off-site electron-phon on correlation plays an important role in the order-disorder transitio n of the spinless case. But in the spin-1/2 case, the Peierls dimeriza tion always exists. The effect of the offsite electron-phonon correlat ion is slight. Our results are in good agreement with Monte Carlo simu lations, and the small squeezed-polaron approach is the special case o f our method.