  We study the propagation of surface plasmon polaritons (SPPs) on a metal
surface which hosts a thin film of a liquid dielectric. The ohmic losses, that
are inherently present due to the coupling of SPPs to conductors' electron
plasma, induce temperature gradients and fluid deformation driven by the
thermocapillary effect, which lead to a nonlinear and nonlocal change of the
effective dielectric constant. The latter extends beyond the regions of highest
optical intensity, and constitutes a novel thermally self-induced mechanism
that affects the propagation of the SPPs. We derive the nonlinear and nonlocal
Schrodinger equation (NNLSE) that describes propagation of low intensity SPP
beams, and show analytically and numerically that it supports a novel optical
spatial soliton excitation.
