Spin-dependent Andreev reflection tunneling through a quantum dot with intradot spin-flip scattering

We study Andreev reflection tunneling through a ferromagnet\char21{}quantum dot\char21{}superconductor system. The intradot spin-flip interaction is considered. By using the nonequilibrium Green function method, an expression for the linear Andreev reflection conductance is derived at zero temperature. It is found that competition between the intradot spin-flip scattering and the tunneling coupling to the leads dominates the resonant behaviors of the Andreev reflection conductance versus the gate voltage. A weak spin-flip scattering leads to a single-peak resonance. However, with the spin-flip scattering strength increasing, the Andreev reflection conductance will develop into a double-peak resonance indicating a novel structure in the conductance tunneling spectrum. Besides, the influences of the spin-dependent tunneling couplings, the Fermi velocity matching condition, and the spin polarization of the ferromagnet on the conductance are examined in detail.