Spin-bias-controlled current rectification and negative magnetoresistance in a quantum dot spin transistor

We propose a spin-bias-controlled quantum-dot spin-valve device and systematically investigate its charge and spin transport properties. Numerical results reveal that the parallel magnetic configuration enables gate-tunable rectification of both charge and spin currents, whereas no rectification occurs in the antiparallel configuration. Remarkably, in specific gate voltage regimes, the device achieves perfect charge rectification — characterized by complete suppression of reverse-bias charge currents — while sustaining finite spin currents. Furthermore, a negative magnetoresistance emerges in this system, electrically tunable to its theoretical minimum of −1, accompanied by an antiparallel to parallel current on/off ratio exceeding 10⁶. This behavior implies that within tailored gate voltage regimes, only the antiparallel configuration permits charge conduction, with electron current entirely blocked in the parallel configuration. These results establish spin-bias-driven quantum dot systems as multifunctional platforms for tunable rectification and magnetoresistance control, highlighting their potential for advancing spintronic technologies.