三端自旋交换耦合双量子点体系的热流特性

Heat Current in Three-terminal Double Quantum Dot System with Spin-exchange Coupling

运用量子主方程方法,研究了三端自旋交换耦合双量子点体系的热流和电流随偏压的变化行为.在电子交换作用为铁磁情况下,偏压较低时两电极量子点的电流和热流出现阻塞现象,这是由于电极的电子费米能低于跃迁量子点多体态之间的能量差.高偏压时,所有输运通道完全打开,电流到达一个平台,但是热流随偏压增加呈线性增长行为.与此不同的是,反铁磁情况下没有出现阻塞现象,因为此时主导输运的跃迁通道能级差较小,更容易产生电流并且到达平台所需的偏压较低.这些结果可以为设计基于量子点的热流器件提供理论依据.

By using the quantum master equation method,the variation of heat and electron current with electric bias is studied in a three-terminal spin-exchange coupled double quantum dot sys-tem.In the ferromagnetic case of electron exchange coupling,the currents through the quantum dot with two electrodes are blocked when the bias voltage is low,because the electron Fermi energy of electrodes is lower than the energy difference between the transition many-body states of quantum dots.At high bias voltage,all transport channels are completely open,and the electronic current reaches a platform,but the heat flow increases linearly with the increase of bias voltage.In contrast,there is no blocking phenomenon in the antiferromagnetic case,because the energy level difference of transition channel that dominates the transport is smaller,it is easier to generate current and the bias required to reach the platform is lower.These results can provide theoretical basis for designing heat current de-vices based on quantum dots.