ELECTRON-PHONON INTERACTION AND SPIN GAP IN NEARLY-HALF-FILLED CORRELATED ELECTRON-SYSTEMS

Renormalization-group equations are solved to study phase diagrams of nearly-half-filled one-dimensional conductors interacting with phonons . A spin-gap charge density wave phase exists between a gapless densit y wave phase and a spin-gap superconductor phase. On-site and intersit e electron-phonon couplings show large differences near half-filling i n the presence of on-site electron repulsion.