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首页> 外文期刊>Physical review >Quantum coherent transport through a quadruple quantum-dot structure with one continuous channel and two concrete channels
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Quantum coherent transport through a quadruple quantum-dot structure with one continuous channel and two concrete channels

机译：通过具有一个连续通道和两个混凝土通道的四重量子点结构进行量子相干传输

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We investigate the coherent transport through a mesoscopic ring composed of four circularly coupled quantum dots (QDs) by means of nonequilibrium Green's functions. Two QDs of the mesoscopic ring with infinite intradot Coulomb interaction serve as two Kondo impurities, which are coupled together by three channels: the direct interdot coupling channel and the other two QD channels. This quadruple QD (QQD) system, including two subrings, is versatile and intriguing due to its advantages in simultaneous studying of the Kondo, Fano, and Aharonov-Bohm effects. We analytically and numerically studied the quantum transport properties of the symmetrical and asymmetrical QQD in both the absence and presence of a magnetic field. First we focus on the linear transport properties without the magnetic field. In the symmetrical QQD, the linear conductance shows a simple pattern with a single peak or double peak when the interdot coupling between two Kondo impurities is weak. However, by increasing this interdot coupling, the conductance evolves into a pattern characteristic of one deep trough. Sharply different from the symmetrical QQD, the conductance in an asymmetrical QQD shows a double peak or triple peak pattern in the case of the weak coupling between two Kondo impurities, and it shows a double trough pattern for the strong coupling. Moreover, we consider the influences on the transport induced by the magnetic field. It is demonstrated that the conductance shows complex oscillations associated with the Kondo, Fano, and Aharonov-Bohm effects, clearly depicting the competitions among them. The oscillation period as a function of magnetic flux is determined by the magnetic-flux ratio threaded into two subrings. The phase rigidity is clearly observed when one intermediate QD energy level passes through the lead Fermi level. Lastly we extend our results into the system with many QD channels used to connect the two Kondo impurities, which gives a complete picture about the transport properties in such a kind of double impurity QD devices.
机译：我们通过非平衡格林函数研究了由四个圆形耦合量子点（QD）组成的介观环的相干传输。具有无限点内库仑相互作用的介观环的两个QD用作两种近藤杂质，它们通过三个通道耦合在一起：直接点间耦合通道和其他两个QD通道。这种四重QD（QQD）系统，包括两个子环，由于在同时研究Kondo，Fano和Aharonov-Bohm效应方面具有优势，因此用途广泛且令人着迷。我们通过分析和数值研究在不存在和存在磁场的情况下对称和不对称QQD的量子传输性质。首先，我们关注没有磁场的线性传输特性。在对称QQD中，当两个近藤杂质之间的点间耦合较弱时，线性电导显示一个具有单峰或双峰的简单模式。但是，通过增加这种点间耦合，电导演变为一个深槽的图案特征。与对称QQD明显不同的是，在两种近藤杂质之间的弱耦合情况下，非对称QQD的电导显示出双峰或三峰模式，而对于强耦合显示出双谷模式。此外，我们考虑了磁场对运输的影响。结果表明，电导显示出与近藤，法诺和阿哈罗诺夫-鲍姆效应相关的复杂振荡，清楚地描述了它们之间的竞争。振荡周期是磁通量的函数，由旋入两个子环的磁通比确定。当一个中间QD能级通过费米能级时，可以清楚地观察到相刚度。最后，我们将结果扩展到具有许多用于连接两种近藤杂质的QD通道的系统，从而全面了解了这种双杂质QD器件的传输特性。

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