Superconductivity in the Alkali-Doped Fullerides: Competition of Phonon-Mediated Attractions with Coulomb Repulsions in Polaron Pairing

The mechanism of superconductivity in the alkali-metal-doped fullerides is investigated theoretically based on the Hubbard–Holstein model. Salient observed features such as the anomalous? C isotope effect on the critical temerature Tc for 50% molecular substitution, the rapid decrease of Tc with the deviation of electron number from half-filling and the difference in the relation of Tc with the lattice constant a0 between fcc and sc structures are explained from a unified viewpoint of polaron pairings originating from the competition between phonon-mediated attractions and Coulomb repulsions.

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