Superconductivity in doped C₆₀: Importance of interband pair delocalization

Abstract

An important factor determining the magnitude of the superconducting transition temperature T _c, of the doped fullerenes is the extent to which the Cooper pair is delocalized over the different bands that cross the Fermi energy E _F,. This point is exemplified by using a simplified Bardeen-Cooper-Schrieffer (BCS) model Hamiltonian to calculate T _c, in terms of the intraband pairing compling constant λ and interband pair-hopping coupling constants λ. ‘If z bands cross E _F the effective weak-coupling BCS coupling constant is λ _BCS = λ + (z – 1) λ’.