HOLE PHONON INTERACTION IN A STRONGLY CORRELATED HUBBARD SYSTEM

Strong interaction between holes (in excess of the half-filled band) and phonons (local) is considered in a strongly correlated Hubbard system. It is shown that the polaron formation around the holes does not affect the antiferromagnetic interaction but it reduces considerably the pair hopping. A two-phonon coherent state for the phonon subsystem is used in order to minimize the free energy of the system. It is found that the band-width of the polaron is very narrow both for low (x≈0) and high (x≈1) hole concentrations whereas the band-width is much larger for the intermediate hole concentrations. This variation of the band-width with the hole concentration leads to a sharp decrease in the polaronic effective mass for x near 0.05 with increasing hole concentration and to a sharp rise for x greater than 0.8. Hole concentration dependence of the resistivity in La-Sr-Cu-O system is consistent with such a behavior of the effective mass. © 1990.