Screening, Coulomb pseudopotential, and superconductivity in alkali-doped Fullerenes

Abstract

We study the static screening in a Hubbard-like model using quantum Monte Carlo. 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 $μ^\ast$ is not very much reduced by retardation effects. Therefore efficient screening is important in reducing $μ^{\ast}$ 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.

4 pages RevTeX with 2 eps figures, additional material available at http://www.mpi-stuttgart.mpg.de/docs/ANDERSEN/fullerene/