Spin-polarized transport through a quantum dot: Anderson model with on-site Coulomb repulsion

We report on a theoretical analysis of transport characteristics of a spin-valve system formed by a quantum dot connecting to two ferromagnetic electrodes whose magnetic moments are oriented at an angle theta with respect to each other. We pay special attention to the effects of a finite on-site Coulomb repulsion U. Using the Keldysh nonequilibrium Green's functions we derived a formula for the current in general terms of bias, temperature, and the parameters theta,U. We have studied the local density of states and nonlinear conductance of this device in the Kondo regime at different polarization angle theta. Our results suggest that the Kondo peaks in the local density of states and in the conductance can be modulated by theta.