  We study the superconducting phase transition, both in a graphene bilayer and
in graphite. For that purpose we derive the mean-field effective potential for
a stack of graphene layers presenting hopping between adjacent sheets. For
describing superconductivity, we assume there is an on-site attractive
interaction between electrons and determine the superconducting critical
temperature as a function of the chemical potential. This displays a
dome-shaped curve, in agreement with previous results for two-dimensional Dirac
fermions. We show that the hopping between adjacent layers increases the
critical temperature for small values of the chemical potential. Finally, we
consider a minimal model for graphite and show that the transition temperature
is higher than that for the graphene bilayer for small values of chemical
potential. This might explain why intrinsic superconductivity is observed in
graphite.
