电子-声子相互作用对平行双量子点体系热电效应的影响

量子点体系是一种典型的低维体系, 该体系的独特物理特性有利于提高热电转换效率. 本文采用非平衡态格林函数方法, 选择平行双量子点结构, 详细讨论了电子-声子相互作用对该体系的电导、热电功率、热电优值以及热导等热电效应相关参数的影响, 全面描述了电子-声子相互作用对该结构中热电效应的影响. 理论计算结果表明, 在低温情况下, 该体系中的法诺干涉能够有效增强热电效应, 而电子-声子相互作用通过破坏法诺干涉而在一定程度上抑制电导以及热导过程. 然而, 电子-声子相互作用不会显著地影响热电功率的幅值, 并且热电优值的极值几乎不会改变, 因此在低温条件下电子-声子相互作用并不是破坏量子点体系热电效应的必要条件. 本文的结果将有利于澄清电子-声子相互作用对量子点体系热电效应的影响.

Influences of electron-phonon interaction on the thermoelectric effect in a parallel double quantum dot system

A quantum-dot system is a typical low-dimensional system, and previous researches showed that its thermoelectric conversion efficiency can be markedy improved due to its unique physical properties. In this poper, we choose the parallel double-quantum-dot structure and discuss the influence of the electron-phonon interaction on the thermoelectric-related parameters, i.e., the electric conductance, thermopower, the figure of merit, and thermal conductance, by using the nonequilibrium Green's function method. Our theoretical calculation results show that under the condition of low temperature, the occurrence of the Fano interference can assist to enhance the thermoelectric effect. When the electron-phonon interaction is taken into account, it can suppress the electric and thermal conductances to a certain extent because of its negative effect on the Fano interterence. However, we readily find that apparently the strengthening of the electron-phonon interaction cannot suppress the maximum of the thermopower. Instead, in some regions, the thermopower has an opportunity to enhance due to the appearance of a new channel caused by the electron-phonon interaction. Meanwhile, the figure of merit is found to cause similar effects to the thermopower. Therefore, in the case of low temperature, the electron-phonon interaction contributes little to the destruction of the thermoelectric effect, namely, it is not the necessary condition for the suppression of the thermoelectric effect. With the increase of temperature, the negative effect of the electron-phonon interaction on the Fano interference becomes relatively distinct, which inevitably weakens the thermoelectric effect. Results of this paper will help to clarify the influence of electron-phonon interaction on the thermoelectric effect.