Superconductivity in Ca-intercalated bilayer graphene

Abstract

Recent observation of proximity effect \cite{Morpurgo:2007} has ignited interest in superconductivity in graphene and its derivatives. We consider Ca-intercalated graphene bilayer and argue that it is a superconductor, and likely with a sizeable $T_{c}$. We find substantial and suggestive similarities between Ca-intercalated bilayer (C$_{6}$CaC$_{6}$), and CaC$_{6} $, an established superconductor with $T_{c}$ = 11.5 K. In particular, the nearly free electron band, proven to be instrumental for superconductivity in intercalated graphites, does cross the chemical potential in (C$_{6}$CaC$% _{6}$), despite the twice smaller doping level, satisfying the so-called \textquotedblleft Cambridge criterion\textquotedblright . Calculated properties of zone-center phonons are very similar to those of CaC$%_{6}.$ This suggests that the critical temperature would probably be on the same scale as in CaC$_{6}$.