ISOTOPIC DISORDER IN SUPERCONDUCTING FULLERENES

The superconducting transition temperature of doped fullerenes appears to be unusually sensitive to partial substitution of C-13 for the nat urally abundant isotope C-12. We show that the electron-phonon couplin g constant lambda is generically independent of isotopic disorder. By studying the effects of isotopic substitution on phonon-mediated super conductivity in C60 within the Migdal-Eliashberg theory we conclude th at the theoretical superconducting transition temperature T(c) does no t show any anomalous dependence on isotopic substitution in weak or st rong coupling. We comment on the possible causes of the experimentally observed effect.