  We review the recent progress in the density functional theory for
superconductors (SCDFT). Motivated by the long-studied plasmon mechanism of
superconductivity, we have constructed an exchange-correlation kernel entering
the SCDFT gap equation which includes the plasmon effect. For the case of
lithium under high pressures, we show that the plasmon effect substantially
enhances the transition temperature (Tc) by cooperating with the conventional
phonon mechanism and results in a better agreement between the theoretical and
experimentally observed Tc. Our present formalism will be a first step to
density functional theory for unconventional superconductors.
