Noncollinear magnetoconductance of a quantum dot

We study theoretically the linear conductance of a quantum dot connected to ferromagnetic leads. The dot level is split due to a noncollinear magnetic field or intrinsic magnetization. The system is studied in the noninteracting approximation, where an exact solution is given, and, furthermore, with Coulomb correlations in the weak tunneling limit. For the noninteracting case, we find an antiresonance for a particular direction of the applied field, noncollinear to the parallel magnetization directions of the leads. The antiresonance is destroyed by the correlations, giving rise to an interaction induced enhancement of the conductance. The angular dependence of the conductance is thus distinctly different for the interacting and noninteracting cases when the magnetizations of the leads are parallel. However, for antiparallel lead magnetizations, the interactions do not alter the angle dependence significantly.