Spin-polarization and Coulomb interaction dependent thermal rectification in a quantum dot system

Yufeng Su, Fenghua Qi, Guojun Jin
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Abstract

Based on the master equation approach, we investigate the thermal transport through a diode composed of a quantum dot under Coulomb interaction and tunnel-coupled to two ferromagnetic leads with antiparallel spin polarizations. We analyze the effects of spin polarizations, Coulomb interaction, mean temperature and Zeeman splitting on the thermal rectification. Firstly, we find that the thermal rectification effect is enhanced with the increase of spin polarization, because the mirror-symmetry of the system is broken by the anti-parallel spin polarization. Especially, when both leads are fully spin polarized, the asymmetry of the heat transferred by Coulomb interaction under the opposite temperature bias leads to the appearance of perfect thermal rectification and negative differential thermal conductance. Secondly, we find whether the system is in a Coulomb blockade state greatly affects the thermal rectification coefficient. As the average temperature increases or the intradot Coulomb interaction decreases, the system gradually escapes from the Coulomb blockade state, resulting in a reversal of the thermal rectification direction and ultimately leading to an increase in the rectification coefficient. Thirdly, we also find that the Zeeman splitting can be utilized to modulate the behavior of thermal rectification. Thermal rectification occurs only when Zeeman splitting and spin polarization coexist, and under different spin polarizations, the rectification coefficient exhibits different trends with the change of Zeeman splitting. These observations indicate that this structure holds potential application at a thermal rectifier as well as a thermal detector of magnetic fields.
量子点系统中取决于自旋极化和库仑相互作用的热整流
基于主方程方法,我们研究了在库仑相互作用下,由量子点组成的二极管与两个自旋极化反平行的铁磁引线的隧道耦合热传输。我们分析了自旋极化、库仑相互作用、平均温度和泽曼分裂对热整流的影响。首先,我们发现热整流效应随着自旋极化的增加而增强,因为反平行自旋极化打破了系统的镜像对称性。特别是当两条导线都完全自旋极化时,在相反的温度偏置下库仑相互作用传热的不对称性导致了完美热整流和负差分热导的出现。其次,我们发现系统是否处于库仑封锁状态对热整流系数有很大影响。随着平均温度的升高或点内库仑相互作用的减弱,系统会逐渐摆脱库仑封锁状态,导致热整流方向逆转,最终导致整流系数增大。第三,我们还发现可以利用泽曼分裂来调节热整流的行为。只有当泽曼分裂和自旋极化同时存在时,热整流才会发生,而且在不同的自旋极化条件下,整流系数会随着泽曼分裂的变化而呈现不同的趋势。这些观察结果表明,这种结构具有热整流和磁场热探测器的应用潜力。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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