Correlation effects on the electron-phonon interaction

The electron-phonon coupling constant (lambda(ph)) is evaluated for the Hubbard Hamiltonian system. It is found that the Coulomb correlation in the Hubbard model gives rise to a phonon hardening and an enhancement of lambda(ph). It is also found that lambda(ph), becomes larger than the electron-spin-fluctuation coupling constant) lambda(sf) for a correlated system with a nearly filled band.