Spin-dependent transport through a serial double-quantum-dot with Rashba spin-orbit interaction

We study the spin-dependent electron transport through a serial double-quantum-dot (DQD) by using Green's function equation of motion technique. Special attention is paid to the functions of the Rashba spin-orbit (RSO) effect in one of the DQD and the inter-dot tunneling coupling tc. When the electrons transport from the left or the right lead into the middle lead, a quasi-two channel is established due to the existence of tc. Then, the RSO interaction will induce into the tunnel matrix element a spin-dependent extra phase factor σϕR as the electrons flowing through different conduction channels, and thus making the current in the middle lead to be spin-polarized. Moreover, by properly adjusting the value of tc, the dot-lead coupling strength, dots' levels and the external bias voltages, a net spin current without the accompanying of charge current can be generated. The structure proposed here is simple and can be realized in the present experiments.