We report a study of spin-dependent transport in a system composed of a quantum dot coupled to a normal metal lead and a ferromagnetic lead NM-QD-FM. We use the master equation approach to calculate the spin-resolved currents in the presence of an external bias and an intradot Coulomb interaction. We find that for a range of positive external biases current flow from the normal metal to the ferromagnet the current polarization =I↑−I↓ / I↑+I↓ is suppressed to zero, while for the corresponding negative biases current flow from the ferromagnet to the normal metal attains a relative maximum value. The system thus operates as a rectifier for spin-current polarization. This effect follows from an interplay between Coulomb interaction and nonequilibrium spin accumulation in the dot. In the parameter range considered, we also show that the above results can be obtained via nonequilibrium Green functions within a Hartree-Fock type approximation.
Bibliographical noteCopyright 2007 American Physical Society
- FERROMAGNETIC TUNNEL-JUNCTIONS
- DEPENDENT TRANSPORT
- DOUBLE-BARRIER JUNCTIONS