Andreev reflection current through a molecule quantum dot in the presence of the electron-phonon interaction and the spin-flip scattering

With the aid of the nonequilibrium Green's function and the Lang-Firsov canonical transformation, we investigate the joint effects of a phononic environment and the spin-flip scattering on the Andreev reflection (AR) in a ferromagnet/single-molecular quantum dot/superconductor (FM/MQD/SC) system. In the presence of the strong electron-phonon interaction (EPI), it is found that the EPI strongly suppresses the AR current (called the Franck-Condon blockade). When the coherent spin-flip (similar to a transverse magnetic field) is taken into account within the MQD, the AR current is significantly enhanced, furthermore, the spin-polarized AR current or even the pure spin-polarized AR current can be generated. By tuning the system parameters, the amplitude and direction of the AR current can be changed, this provides an efficient mechanism for controlling the AR process. (C) 2010 Elsevier B.V. All rights reserved.