串接耦合量子點在線性與非線性響應的傳輸及熱電行為之探討

The study of charge transport and thermoelectrical properties of serially coupled quantum dots in the linear and nonlinear responses

李汶洛(Wen-luo Li)

指導教授 ： 郭明庭

國立中央大學/資訊電機學院/電機工程學系/碩士(2015年)

摘要

本論文探討串接耦合量子點連接金屬電極在線性與非線性響應區域間的傳輸及熱電特性。我們使用延展的哈伯模型和安德森模型來描述串接耦合量子點接面系統之電子總能，並藉由凱帝旭格林函數的技術得到流經串接耦合量子點接面的穿隧電流和熱流。在包利自旋阻斷條件下，我們研究串接耦合量子點的電流整流和負微分電導之行為。除此之外，在線性響應區，我們亦分析電導和席貝克係數。我們觀察到電導的非熱增寬現象和透過席貝克係數的變化可分辨量子點內電子自旋組態，驗證了串接耦合量子點系統可同時作為一個自旋過濾器和低溫電流過濾器。最後，我們討論了以兩端金屬電極溫差來驅動串接耦合量子點接面穿隧電流的機制，並且發現到與量子點能階高低相依的熱電流之非線性傳輸行為。

關鍵字

量子點 ； 熱電 ； 自旋阻斷 ； 席貝克係數

並列摘要

We theoretically study the charge transport and thermoelectric properties of a serially coupled quantum dots (SCQDs) connected to the metallic electrodes in the linear and nonlinear response regimes by the extended Hubbard model and Anderson model. The charge and heat currents of SCQDs are calculated by the Keldysh-Green function technique. We investigate the current rectification and negative differential conductance of SCQDs under the Pauli spin blockade (PSB) condition in the nonlinear response regime. The nonthermal broadening effect of tunneling current in the PSB process is observed. This demonstrates that SCQDs can act as spin filters and low-temperature current filters simultaneously. In the linear response regime, the electrical conductance and Seebeck coefficient (S) are also analyzed. The temperature-dependent S can reveal the spin configuration by examining the sign change of S. Finally, we have investigated the tunneling current of SCQDs driven by a temperature bias and observed the nonlinear thermal currents which depend on the QD energy levels .

並列關鍵字

quantum dot ； thermoelectric ； spin blockade ； Seebeck coefficient

參考文獻

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