Nonadiabatic channels in the superconducting pairing of fullerides
We show the intrinsic inconsistency of the conventional phonon mediated theory of superconductivity in relation to the observed properties of Rb3C60. The recent, highly accurate measurement of the carbon isotope coefficient alpha(C) = 0.21, together with the high value of T(c) (30 K) and the very small Fermi energy E(F) (0.25 eV), unavoidably implies the opening of nonadiabatic channels in the superconducting pairing. We estimate these effects and show that they are actually the key elements for the high value of T(c) in these materials compared to the very low values of graphite intercalation compounds.
Cappelluti
E
Dipartimento di Fisica, Universita di Roma "La Sapienza," Piazzale A. Moro, 2, 00185 Roma, Italy and Istituto Nazionale Fisica della Materia, Unita di Roma 1, Italy.
Grimaldi
C
Pietronero
L
Strassler
S