量子点和一维量子线相耦合系统在Kondo区物理性质的研究

发布时间：2018-06-15 08:44

本文选题：量子点 + 非平衡格林函数　；参考：《北京工业大学》2015年硕士论文

【摘要】：由于设计和制作纳米尺寸的电子器件的需要,低维纳米体系的量子输运性质的研究成为了当前凝聚态物理领域的一个热点。对低维纳米体系的电子输运的研究有助于我们对电子强关联性质有更深的理解。本论文采用非平衡格林函数方法、运动方程方法和玻色化技术研究了低维纳米体系的电子输运现象,其目的在于揭示对低维纳米体系的新物理效应和物理机制,以及解释相关的物理实验现象,并为设计和实现具有优良性能的纳米电子器件提供理论依据和物理模型。本论文共分五章。第一章和第二章分别介绍了相关理论研究背景和理论技术方法。其余三章介绍了本论文的研究工作。首先,本论文我们提出了对量子点和Luttinger液体耦合的系统在近藤区的量子输运性质进行了详细的理论研究。数值模拟结果显示在近藤区微分电导G(V,T)Vbμ显示出随偏压的幂率变化关系,以及零偏压电导随温度变化的幂率变化关系,G(0,T)Tbμ,指数是b=2/g-2,这里g与Luttinger液体中电子相互作用参数有关,这些幂律变化关系与实验结果非常相吻。我们发现了线性电导随温度变化的峰值maxG(T)在不同温度区域的不同特点:(1)对于非常低的温度T,1maxG Tb-μ;(2)对于相对低的温度T,maxG Tbμ;(3)对于高温TG,/2 1maxG(T)Tb-μ;这些不同的温度区域电导峰值随温度不同变化幂律关系与不同的输运机制有关,给出了从低温到高温的完整温度去的变化特性及规律。与此同时,这个幂律变化关系也解释了2003年-2005年理论上和实验上所给出的不同幂指数问题。其次,本论文研究了量子线内电子相互作用和量子点上的库伦相互作用共同对量子点与量子线相耦合体系在近藤区的量子噪声的影响。本论文首先运用非平衡格林函数、运动方程以及玻色化技术推导出了此纳米体系的噪声公式,并根据此公式进行了数值模拟,数值结果显示对于弱量子线内相互作用,噪声随偏压变化曲线中,在近藤温度Tk附近的噪声峰高随量子线内相互作用减弱而降低,而峰的位置几乎保持不变,显示出单沟道近藤效应。这有助于通过散粒噪声测定可靠地估计近藤温度。但是随着量子线内相互作用的增强,噪声峰最后消失,表明了单购近藤效益消失,并从单沟道近藤效益向到双沟道近藤效应转变。数据拟合显示量子噪声随偏压呈现幂律变化关系。我们也计算了Fano因子:散粒噪声S与电流I的比值,F=S/2e I。数值结果显示随量子线内相互作用增强Fano因子增大。这个结果揭示了可以通过调制材料参数来控制Fano因子大小。最后,在这一部分我们研究了量子线内电子相互作用和量子点与量子线间的库伦相互作用共同对量子点和Luttinger液体导线相耦合在近藤区非平衡输运性质的影响。首先,应用正则变换技术,消去了量子点与量子线间的库伦相互作用,并把这个它转移到隧穿哈密顿中,同时,重整化了量子点与量子点上的库伦相互作用;也重整化了量子线内的电子相互作用。数值拟合结果显示量子相变的出现。当重整化相互作用参数Y≈1时,出现近藤效应;当Y1时,隧穿效应增强,单沟道相出现。卫星dips变为峰。当Y1时,近藤峰高度降低,并转化为近藤dip,出现了双沟道近藤效应。单沟道与双沟道。对效应在Y≈1发生相变。Y1和Y1,分别对应量子点和Luttinger液体导线之间的隧穿效应分别抑制和增强,它们反映了两种不同类型的激子辅助隧穿效应。这些物理现象为将来的实验中研究双沟道近藤物理及相变提供了理论方法和依据。
[Abstract]:Due to the need for the design and fabrication of nanoscale electronic devices, the study of the quantum transport properties of the low dimensional nanoscale has become a hot spot in the field of condensed matter physics. The study of the electron transport of the low dimensional nanoscale system will help us to have a deeper understanding of the strong correlation properties of the electrons. This paper uses the nonequilibrium Green function. Methods, motion equations and boson techniques are used to study the electron transport of low dimensional nanoscale systems. The purpose is to reveal new physical and physical mechanisms for low dimensional nanoscale systems, and to explain the related physical experimental phenomena, and to provide theoretical and physical models for the design and implementation of nanoscale devices with excellent properties. This thesis is divided into five chapters. The first and second chapters introduce the relevant theoretical research background and theoretical and technical methods respectively. The other three chapters introduce the research work of this thesis. First, we present a detailed theoretical study of quantum transport properties of quantum dots and Luttinger liquid coupled systems in the rattan area. The results of the value simulation show that the relationship between the power rate variation with the bias voltage and the power rate variation of the zero bias electrical conductivity with the temperature change, G (0, T) Tb mu, the exponent is b=2/g-2, and the G and Luttinger liquids are related to the electron interaction parameters, and the relationship between the power law and the experimental results is very close to the experimental results. The different characteristics of the peak maxG (T) of the linear conductivity with the temperature change were found in different temperature regions: (1) for very low temperature T, 1maxG Tb- mu; (2) for relatively low temperature T, maxG Tb mu; (3) for high temperature TG, /2 1maxG (T). At the same time, this power law relationship also explains the different power exponents given in theory and experiment in -2005 in 2003. Secondly, this paper studies the interaction of the electron in quantum lines and the interaction of the Kulun interaction on the quantum dots. The influence of quantum dots and quantum wire coupled system on the quantum noise in the rattan area. This paper first derives the noise formula of the nanoscale system by using the nonequilibrium Green function, motion equation and boson technique, and the numerical simulation is carried out according to the formula. The numerical results show the interaction within the weak quantum line, and the noise is biased with the bias. In the variation curve, the height of the noise peak near the rattan temperature Tk decreases with the interaction of the quantum wire, and the position of the peak is almost invariable, showing the effect of the rattan effect in the single channel. This helps to reliably estimate the temperature of the rattan through the determination of the particle noise. But with the enhancement of the quantum wire interaction, the noise peak is finally disappearing. It is clear that the benefit of the single purchase of the near rattan vanishes, and changes from the benefit of the single trench to the rattan. The data fitting shows the relationship between the quantum noise and the bias voltage. We also calculated the ratio of Fano factor: the ratio of the particle noise S to the current I, and the F=S/2e I. numerical results show that the enhancement of the Fano factor increases with the interaction of the quantum wire. The results reveal that the size of the Fano factor can be controlled by the modulation of the material parameters. Finally, in this part, we have studied the effect of the interaction of the quantum wires and the interaction of quantum dots and the quantum wires between the quantum dots and the quantum wires on the nonequilibrium transport properties of the quantum dots and the Luttinger liquid wire in the rattan region. First, the application of the Fano is positive. The transformation technique eliminated the interaction between the quantum dots and the quantum lines of Kulun and transferred it to the tunneling Hamilton, and reformed the interaction between the quantum dots and the Kulun on the quantum dots, and reformed the electron interaction within the quantum wire. When the parameter Y is 1, there is a near rattan effect. When Y1, the tunneling effect is enhanced and the single channel phase appears. The satellite dips becomes the peak. When Y1, the height of the near rattan peak is reduced and converted to rattan dip. The effect of the double channel and the double channel appears in the double channel. The effect of the phase transition.Y1 and Y1 of the effect is between the quantum dots and the Luttinger liquid wires respectively in Y. The tunneling effect is suppressed and enhanced respectively. They reflect two different types of exciton assisted tunneling effect. These physical phenomena provide a theoretical method and basis for the study of the physics and phase transition of the double channel in the future.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O471.1

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