Spin-momentum locking in optical rectification

Spin-momentum locking is intriguing and observable optically in the surface-plasmon polariton (SPP) waves. Here, we report on its direct electrical detection. In a periodically patterned metallic surface, a circularly polarized light incident in the Y direction generates a unidirectional SPP by spin-momentum locking in the X direction and was detected via optical rectification at the sample edge in the form of a DC voltage or current.