Spin transport through a double quantum-dot system with tunable magnetic field

The spin transport in a double quantum-dot system with tunable magnetic field was investigated by non-equilibrium Green function method. For two unidentified quantum dots (QDs), it is found that in comparison with the situation without magnetic field on the QDs, the average spin occupations separate with the increase in the magnetic field, which resemble the behaviors as observed in a single-dot system, however, the magnetic field applied on them is only the tenth of that on single dot system. On the other hand, for two identified QDs, the magnetic field has profound effect on the current for different spins in the QDs. Especially for different magnetic fields, the threshold voltage for up spin shifts higher as the difference increasing, while it for down spin is lower. In addition, the spin polarization of current presents correspondingly novel performances, such as, an unexpected dip. It is suggested that the system is a favorable candidate for spintronic devices or external field detectors.