Thermally driven unipolar and bipolar spin diode based on double quantum dots

Abstract

Using the master equation approach, we theoretically propose a unipolar spin diode consisting of two serially coupled quantum dots connected to two normal metal electrodes, in which the two electrodes have different temperatures, and the two dots have different Zeeman splittings. The current through this system can be from zero to nearly 100% spin-polarized by tuning the difference of the electrode temperatures or the gate voltages applied to the quantum dots. This particular transport property is attributed to the interplay of the strong intradot Coulomb interactions, the asymmetrical energy level distributions in the two dots induced by the different Zeeman splittings and different Fermi distributions in the two electrodes caused by different temperatures. Also, a bipolar spin diode can be designed using the two unipolar spin diodes. These configurations may provide the essential elements for the design of logic circuits and even magnetic heads.