A proposal of a spin cell using light on magnetic tunneling junctions

We propose and theoretically investigate a spin cell using light as the power source. Such a device can be realized when a quantum dot is connected to two ferromagnetic electrodes. In the case of identical electrodes, a pure spin current (PSC) can be generated when the light is shone on the quantum dot. Moreover, the PSC can be tuned continuously from zero to the maximum when the magnetic moment orientations of the two electrodes are changed from parallel to anti-parallel. The output spin bias is linear with the light power in the low power region, while it approaches the theoretical limit when the power is extremely high because of the electrodes' renormalization by the spin transfer torque. This effect implies that light energy can be transferred to electron spin directly, which may be applicable in future opto-spintronics.