Temperature gradient controlled spin current rectification in a semiconductor quantum dot

Abstract

In this work, we theoretically propose a thermally controlled spintronic device comprising a semiconductor quantum dot weakly coupled to a pair of nonmagnetic electrodes. Inspired by a graphene quantum wire in Sierra et al. [Nat. Nanotech. 13, 107], a slight asymmetry exists between the two spin channels in one of the nonmagnetic electrodes. Our calculations demonstrate that the thermal spin current exhibits a pronounced asymmetric distribution as the temperature gradient varies, and this asymmetry can be precisely modulated by the quantum dot’s energy level via gate voltage. Notably, in specific gate voltage regimes, even a small temperature gradient can completely suppress the spin current to zero, while the charge current’s symmetry remains unaffected. We further investigate the rectification effect of the temperature gradient on the spin current under various parameters, elucidating the underlying physical principles and operational mechanisms. Additionally, under specific conditions, the system can generate a pure spin current (with a net charge current of zero), which can still be effectively regulated by the temperature gradient to achieve unidirectional flow. These findings provide a novel strategy for the generation and manipulation of spin currents in spintronics applications, and we believe these results can be experimentally verified.