High-resolution thermal expansion of superconducting fullerides A3C60(A=K,Rb)

Abstract

The thermal expansion of air-sensitive A3C60 compounds (A=K,Rb) was investigated using a high-resolution capacitance dilatometer operating in an inert atmosphere. The discontinuity in the linear thermal expansivity at the superconducting transition, Δα, of each compound is presented, from which we determine the corresponding discontinuity in the specific heat ΔcpTc, via the Ehrenfest relation (75±14 mJ/mol K2 for Rb3C60 and 64±14 mJ/mol K2 for K3C60). On the basis of the calculated ΔcpTc values, the density of states N(EF) and the electron-phonon coupling constant λ are derived using the McMillan strong-coupling formalism and recent theoretical results. We find N(EF)=6.6±1.1 states/eV spin C60 and 7.4±1.0 states/eV spin C60 for K3C60 and Rb3C60, respectively. The associated λ is estimated to be ∼0.5 for both K3C60 and Rb3C60. The ratio N(EF)Rb3C60N(EF)K3C60 is consistent with a superconducting mechanism involving high-frequency intramolecular phonons.

Source-reported materials — not catalogue approval

Similar papers