Temperature-manipulated spin transport through a quantum dot transistor

We study the spin-polarized transport through a semiconductor quantum dot connected to a normal metal lead and a ferromagnetic lead, applied with different temperatures. Using the master equation approach, it is found that in such a system the spin polarization of thermal current has a rectification effect; that is, in the positive temperature bias range, the current polarization has a nonzero plateau, while in the negative temperature bias range, the current polarization vanishes. In addition, the current polarization exhibits a spin-valve effect, which corresponds to the existence of a finite zero region controlled by the gate voltage, and the size of the zero region is determined by Coulomb interaction and temperature bias.