Photo-spin-voltaic effect

The photo-voltaic effect typically occurs in semiconductors and involves photon-driven excitation of electrons from a valence band to a conduction band. In a region such as a p-n junction that has a built-in electric field, the excited electrons and holes diffuse in opposite directions, resulting in an electric voltage. This letter reports that a spin voltage can be created by photons in a non-magnetic metal that is in close proximity to a magnetic insulator: a photo-spin-voltaic effect. The experiments use platinum/magnetic insulator bilayer structures. On exposure to light, there occurs photon-driven, spin-dependent excitation of electrons in several platinum atomic layers near the platinum/magnetic insulator interface. The excited electrons and holes diffuse in different manners, and this gives rise to an effective spin voltage at the interface and a corresponding pure spin current that flows across the platinum.