Optically controlled spin-dependent Andreev reflection and spin accumulation in a quantum dot

We theoretically investigate the Andreev reflection and the spin accumulation in a quantum dot subjected to a continuous circularly polarized optical irradiation. Due to the optical pumping effects, electrons having a certain spin experience the Rabi oscillation and their energy levels are shifted by the Rabi frequency. Correspondingly, only electrons with certain spin can contribute to the current by adjusting the dot level and the bias voltage. The Andreev reflection current thus becomes spin dependent and exhibits a tunable spin polarization. Furthermore, the electron occupation number in the quantum dot also becomes spin dependent and exhibits a strong spin accumulation. The magnitude and direction of the spin accumulation in the quantum dot can be easily controlled by tuning the dot level and the bias voltage. This provides an efficient mechanism to control the Andreev reflection and spin accumulation in the quantum dot.