ADIABATIC AND NONADIABATIC ELECTRON INTRAMOLECULAR-VIBRATION COUPLINGS AND SUPERCONDUCTIVITY IN FULLERENES

We have studied adiabatic and nonadiabatic electron-intramolecular-vibration (e-MV) couplings in doped C60. We have shown that nonadiabatic e-MV couplings in the multiband system bring about an interband pair transfer interaction to give T(c) enhancement. We have estimated the adiabatic and the nonadiabatic e-MV coupling constants of the doped C60. The dimensionless adiabatic e-MV coupling constants with the lowest three h(g) modes are large (0.2-0.4) and they dominate the e-MV couplings in doped C60. The dimensionless nonadiabatic e-MV coupling constants of h(g) modes are estimated to be 0.02-0.12. They cannot be neglected in quantitative arguments. The nonadiabatic e-MV coupling may be important even in qualitative arguments of the mechanism of superconductivity if (i) the interband interaction is enhanced by many-body effects and/or if (ii) the nonadiabatic e-MV coupling of A3C60 is larger by a factor of 2 or 3 than that of the dilute limit which we have estimated.