Spin to Charge Interconversion Phenomena in the Interface and Surface States

In 1985, Johnson and Silsbee realized the creation of a spin current in nonmagnetic metals, which inspired a vast number of studies related to the spin current until now. Creation of the spin current has been realized in metals, semiconductors, and insulators to date and has provided a fruitful research field. Spin-dependent conductance and spin torque paved a new way for spintronic application, and highly efficient interconversion between spin information and an industrially used one, such as charge current, light, magnetic moment and heat current, became a central topic. In the early stage, the main field of such interconversion was bulk materials; the focus then gradually shifted to surface and interface states. The properties of surface and interface states became pronounced in nanoscale spintronics devices, and a variety of functions have been realized at the interface between two materials, enabling limitless possibilities for spin functions. This review provides an overview of the recent progress of the spin-charge interconversion in the surface and interface states. We also introduce several spurious effects that should be paid careful attention for quantitative investigations.