COULOMB PSEUDOPOTENTIAL, SCREENING AND SUPERCONDUCTIVITY IN C-60

We estimate the Coulomb pseudopotential mu* for a model of undoped C60, renormalizing away all subbands but the t1u conduction band by summing ladder diagrams in the screened interaction. The renormalization of mu* is small. For doped C60 the screened U is calculated. A very efficient metallic screening is found for the intraband U, but not for the interband U, suggesting a large renormalization of mu* within a ladder diagram approach. Exact results for a two-band model suggest, however, that the ladder diagrams strongly overestimate the renormalization.