Spin angular momentum transfer and plasmogalvanic phenomena

We show that spin angular momentum (SAM) of light is transferred to matter together with momentum and energy, and obtain the expression for the corresponding torque. This can lead to appearance of spin forces, which correspond to the discrepancy between the Lorentz and Einstein-Laub forces. In plasmonic metals these spin forces result in a plasmogalvanic phenomenon, which is pinning of the plasmon-induced electromotive force to an atomically thin layer at the metal interface.