  We study the interband self-induced transmission of surface plasmon
polaritons in a gold film surrounded by an external Kerr medium. We model the
optical propagation by using a version of the generalized nonlinear Schrodinger
equation for the field envelope coupled to Bloch equations for valence
electrons of gold, predicting self-induced transparency of ultrashort plasmon
solitons with a pulse duration below 10 fs. We demonstrate that the Kerr
nonlinearity from the surrounding dielectric can be used to compensate for the
group velocity dispersion, and that the impact of dephasing and decay processes
can be effectively reduced by the self-induced transmission mechanism.
