Mechanisms of superconductivity phase transition in molecular solids: the case of doped fullerenes

The surprising discovery of superconductivity at high temperature in doped fullerenes (C60: icosahedral hollow cluster balls of 60 carbon atoms) has posed another challenge regarding the possible mechanisms of superconducting phase transitions in such molecular systems. In the present communication, the molecular, crystal and electronic structure of the fullerenes have been discussed and the mechanism of superconductivity in alkali doped fullerides MxC60(M=K, Rb, Cs, Tc etc) is developed. The mechanism comprises a combination of phonon and high energy electronic boson exchange as in the case of cuprates. The electronic boson process involves bond polarization in interaction with conduction electrons. The theory accounts for the high transition temperature (Tc) observed in these systems. Further, predictions based on this mechanism are consistent with the observed isotope effect and the superconducting energy gap in M3C60 fullerides. (author). 15 refs