Surface-mediated effect on electron spin dynamics probed by optical-pump-probe scanning tunneling microscopy

In current material science and technologies, surface effects on the carrier and spin dynamics in functional materials and devices are of great importance. In this paper, we present the surface-sensitive probing of electron spin dynamics, achieved by the optical-pump-probe scanning tunneling microscopy (OPP-STM). Time-resolved spin lifetime information on a manganese (Mn)-deposited GaAs (110) surface was successfully obtained for the first time. With increasing Mn density via in situ evaporation, a nonlinear change in the spin lifetime in the picosecond range was clearly observed, while directly confirming the Mn density by STM. By comparison with results obtained by the conventional OPP method, we have also demonstrated that the observed nonlinear spin lifetime behevior was surface-mediated, which can be characterized using only the surface-sensitive OPP-STM technique.