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arXiv 0907.3169cond-mat.mes-hallcond-mat.str-el
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通过侧耦合到量子点的量子线的通用零偏压电导

Universal zero-bias conductance through a quantum wire side-coupled to a quantum dot

A. C. Seridonio, M. Yoshida, L. N. Oliveira

摘要:

用数值重整化群方法研究了量子线与量子点的耦合电导。研究了嵌入量子点的对称Anderson量子线模型的电导随温度和量子点能量的变化关系,得到了近藤区电导随温度变化的线性映射和描述电导的普适函数.确定了两条导电路径,一条穿过导线,另一条通过量子点的旁路。示出了施加到量子线的栅极电势以控制通过旁路的流量。当电位有利于通过导线传输时,近藤区的电导从低温时的近零上升到高温时的近弹道。当它倾向于点时,模式相反:电导从接近弹道衰减到接近零。当通过这两个路径的通量是可比的,电导是近藤制度几乎与温度无关,和Fano反共振的固定温度图的电导作为点能量信号干扰的函数。在整个近藤制度,在低温下,即使在混合价制度,数值数据是在很好的协议与普遍的映射。

英文摘要:

A numerical renormalization-group study of the conductance through a quantum wire side-coupled to a quantum dot is reported. The temperature and the dot-energy dependence of the conductance are examined in the light of a recently derived linear mapping between the Kondo-regime temperature-dependent conductance and the universal function describing the conductance for the symmetric Anderson model of a quantum wire with an embedded quantum dot. Two conduction paths, one traversing the wire, the other a bypass through the quantum dot, are identified. A gate potential applied to the quantum wire is shown to control the flow through the bypass. When the potential favors transport through the wire, the conductance in the Kondo regime rises from nearly zero at low temperatures to nearly ballistic at high temperatures. When it favors the dot, the pattern is reversed: the conductance decays from nearly ballistic to nearly zero. When the fluxes through the two paths are comparable, the conductance is nearly temperature-independent in the Kondo regime, and a Fano antiresonance in the fixed-temperature plot of the conductance as a function of the dot energy signals interference. Throughout the Kondo regime and, at low temperatures, even in the mixed-valence regime, the numerical data are in excellent agreement with the universal mapping.

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