Metallic Screening and Correlation Effects in Superconducting Fullerenes

We consider the frequency-dependent Coulomb interaction between electrons in a molecular metal in the limit in which the conduction bandwidth is much less than the plasma frequency, which in turn is much less than intramolecular excitation energies. In particular, we compute the effective interactions at the Fermi energy in alkali-doped ${\mathrm{C}}_{60}$ to second order in the screened interactions. The frequency dependence of screening substantially reduces the effects of the long-range part of the Coulomb interaction, leading to the possibility of effective attraction between electrons.