We propose a mechanism of angular momentum conversion from optical transverse spin in surface plasmon polaritons (SPPs) to conduction electron spin. Free electrons in the metal follow the transversally spinning electric field of the SPP, and the resulting orbital motions create inhomogeneous static magnetization in the metal. By solving the spin diffusion equation in the SPP, we find that the magnetization field generates an electron spin current. We show that there exists a resonant condition where the spin current is resonantly enhanced, and the polarization of the spin current is flipped. Our theory reveals an alternative functionality of SPPs as a spin current source.

• Received 5 July 2019
• Revised 27 March 2020
• Accepted 1 April 2020

DOI:https://doi.org/10.1103/PhysRevB.101.161404