Specific-heat jump at Tc and normal-state magnetic susceptibility of A3C60.

Abstract

We have measured the normal-state susceptibility \ensuremath{\chi} for both ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$ and ${\mathrm{Rb}}_{3}$${\mathrm{Cu}}_{60}$ and the specific heat jump \ensuremath{\Delta}C at the superconducting ${\mathit{T}}_{\mathit{c}}$ for ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$. Within a phonon-mediated pairing model, the combined effects of \ensuremath{\chi} and \ensuremath{\Delta}C are shown to give strong support to pairing via high-energy modes (g1000 K) associated with intramolecular vibrations. In addition, the small \ensuremath{\Delta}C along with the known upper critical field slope provide evidence for an extreme dirty-limit superconductor, with mean free path l\ensuremath{\approxeq}10 \AA{}.