Theory of Superconductivity in Graphite Intercalation Compounds

On the basis of the model that was successfully applied to KC8, RbC8, and CsC8 in 1982, we have calculated the superconducting transition temperature Tc for CaC6 and YbC6 to find that the same model reproduces the observed Tc in those compounds as well, indicating that it is a standard model for superconductivity in the graphite intercalation compounds with Tc ranging over three orders of magnitude. Further enhancement of Tc well beyond 10 K is also predicted. The present method for calculating Tc from first principles is compared with that in the density functional theory for superconductors, with paying attention to the feature of determining Tc without resort to the concept of the Coulomb pseudopotential.