Gunnarsson O., Koch E., Martin R. M.
It is discussed why K3C60 and Rb3C60 fullerenes are metals and not Mott-Hubbard insulators, in spite of the strong Coulomb repulsion. The orbital degeneracy N of the t1u-band increases the crit. value of Coulomb repulsion for the Mott-Hubbard transition by about a factor of .sqroot.N. Theor. and exptl. ests. of the electron-phonon coupling are discussed. In particular, photoemission for free C60- mols. can be used to est. the coupling. The Coulomb pseudopotential describing the effects of the Coulomb repulsion is discussed. In particular the retardation effects are considered. The pseudopotential is relatively large, but the results are still consistent with the electron-phonon interaction driving the supercond.
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