  We investigate the possibility of inducing superconductivity in a graphite
layer by electronic correlation effects. We use a phenomenological microscopic
Hamiltonian which includes nearest neighbor hopping and an interaction term
which explicitly favors nearest neighbor spin-singlets through the well-known
resonance valence bond (RVB) character of planar organic molecules. Treating
this Hamiltonian in mean-field theory, allowing for bond-dependent variation of
the RVB order parameter, we show that both s- and d-wave superconducting states
are possible. The d-wave solution belongs to a two-dimensional representation
and breaks time reversal symmetry. At zero doping there exists a quantum
critical point at the dimensionless coupling J/t = 1.91 and the s- and d-wave
solutions are degenerate for low temperatures. At finite doping the d-wave
solution has a significantly higher Tc than the s-wave solution. By using
density functional theory we show that the doping induced from sulfur
absorption on a graphite layer is enough to cause an electronically driven
d-wave superconductivity at graphite-sulfur interfaces. We also discuss
applying our results to the case of the intercalated graphites as well as the
validity of a mean-field approach.
