Switching performance of optically generated spin current at the graphene edge

We investigate the response of the optically generated spin current as a function of time at the graphene edge for a possible application of optospintronic devices. The spin current is generated by optically excited edge plasmon in which the induced electric field is rotating on the graphene plane. According to the inverse Faraday effect, the in-plane rotation of electric field generates magnetization in the direction perpendicular to the graphene plane. The diffusive spin current flows by decaying distribution of the magnetization from the edge. By solving the time-dependent, diffusion equation in the presence/absence of the spin-source term, we evaluate the on/off response of spin current. The switching speed becomes fast when the spin-diffusion length is sufficiently large compared with the decaying length of the magnetization.