Area theorem for surface plasmons interacting with resonant atoms

We show how the area theorem is applicable to the analytical description of the nonlinear interaction of surface plasmon modes with resonant two-level atoms. A closed analytical solution is obtained and analyzed for a dielectric-negative index metamaterial interface, which shows that surface plasmons can form long-propagating $2\ensuremath{\pi}$ pulses when interacting with an optically dense two-level atomic ensemble. The possible applications of the surface pulse area theorem and the conditions for the detection of $2\ensuremath{\pi}$ surface plasmon pulses are discussed.