ELECTRON-PHONON INTERACTION OF STRONGLY CORRELATED SYSTEMS - II - STRONG-COUPLING LIMIT

The Hubbard model supplemented by the Holstein interactions between el ectrons and optical dispersionless phonons is investigated under the a ssumption of strong coupling. The collective mode is found for the pho non cloud surrounding the polaron and the effect of the processes of a bsorption and emission of this mode on the energy spectrum is establis hed for both localized and delocalized polarons. The motion of delocal ized polarons due to their site-to-site jumping is described in the ch ain-diagram approximation in which the many-particle irreducible Green 's functions of the polaron are neglected. The resulting electron ener gy spectrum consists of four subzones.