Andreev reflection through a ferromagnet-quantum dot-superconductor system with intradot Coulomb correlations

Spin-dependent tunneling through a quantum dot coupled to one ferromagnetic and one superconducting electrodes is studied in the Andreev reflection (AR) regime. Electrical conductance is calculated within the nonequilibrium Green function technique. Effects due to a competition between the Coulomb correlations on the dot and intradot spin-flip processes are considered in the linear transport regime and for different coupling strengths between the dot and the external electrodes. It is shown that when a coherent spin rotation is present on the dot, Coulomb interactions may lead to a significant enhancement of the AR tunneling current and even to the perfect AR transmission. Origin of occurrence of a variety of the multipeak structure of the linear conductance is also discussed.