We study the static screening in a Hubbard-like model using quantum Monte Carlo methods. We find that the random phase approximation is surprisingly accurate almost up to the Mott transition. We argue that in alkali-doped fullerenes the Coulomb pseudopotential mu * is not very much reduced by retardation effects. Therefore efficient screening is important in reducing mu * sufficiently to allow for an electron-phonon driven superconductivity. In this way the fullerides differ from the conventional picture, where retardation effects play a major role in reducing the electron-electron repulsion.
A reprint of this paper can be obtained here.
Physical Review Letters, 83 620-3, 1999.
Max-Planck Institut für Festkörperforschung;
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