Isotope Effect in Superconducting Fullerenes

Abstract

The effect of isotopic substitution on the superconducting transition temperature, T_c, in alkali-doped C₆₀ has been examined. Paradoxically, it is found that a substantial decrease in T_c with the increasing isotopic mass is possible even when the attractive interaction is not mediated by phonons but is instead of purely electronic origin. In particular, it is shown that the experimentally measured isotopic shifts are consistent with a recently proposed electronic mechanism. Further predictions are presented that can be tested by experiment.