Dynamic modulation of electron correlation by intramolecular modes in charge-transfer compounds

Electron-phonon and electron-electron interactions are in competition in de termining the properties of molecular charge-transfer conductors and superc onductors. The direct influence of phonons on the electron-electron interac tion was not before considered and in the present paper the coupling of int ramolecular modes to electron-electron interaction (U-vib interaction) is i nvestigated. The effect of this coupling on the frequency of the normal mod es of a dimer model is obtained and it is shown that frequency shifts of th e Raman active modes are directly related to this coupling. The results are used to obtain the values of the U-vib coupling constants of intramolecula r modes of a representative molecule of charge-transfer conductors, like te tramethyl-tetratiafulvalene. Consequences of this coupling on the electron pairing are also suggested. [S0163-1829(99)01444-7].