9 pages, 6 figures; To appear in PRB. Revised version: includes derivation of exact sum rules, analytical approximation for the spin noise, and additional details of the NRG calculation
Magnetic and charge noise have common microscopic origin in solid state devices, as described by a universal electron trap model. In spite of this common origin, magnetic (spin) and charge noise spectral densities display remarkably different behaviours when many-particle correlations are taken into account, leading to the emergence of the Kondo effect. Our numerical renormalization group results indicate that while spin noise is a universal function of the Kondo temperature, charge noise remains well described by single-particle theory even when the trap is deep in the Kondo regime. This difference survives even in the presence of disorder, showing that noise can be more manageable in devices that are sensitive to magnetic (rather than charge) fluctuations and that the signature of the Kondo effect can be observed in spin noise spectroscopy experiments.
Fano-Kondo resonance versus Kondo plateau in an Aharonov-Bohm ring with an embedded quantum dot
我们从理论上研究了通过Aharonov-Bohm环与嵌入的量子点（QD），所谓的QD干涉仪，解决两个有争议的问题，库仑峰的形状和测量的传输相移通过QD。我们推广了一个已有的模型[B. R. Bulka和P. Stefanski，Phys. Rev. Lett. 86，5128（2001）; W. Hofstetter，J. Konig，and H. Schoeller，同上，87，156803（2001）]考虑两个外部导联L和R中的多个传导通道。我们引入一个参数p_α（|p_α| \le 1）通过导联α（=L，R）表征环的两个臂之间的连接，其是耦合到两个臂的传导模式之间的重叠积分。首先，我们研究了在没有电子-电子相互作用U的情况下，电导峰的形状作为量子点中能级的函数。我们证明了一个不对称的Fano共振，|p_{L,R}| = 1的情况下，导线中的单传导通道和几乎对称的Breit-Wigner共振，|p_{L,R}|在多个通道的情况下< 0.5。其次，在U存在的情况下，Bethe近似精确解考虑了近藤效应。我们精确地评估了温度T=0时的电导，并显示出从不对称的Fano-Kondo共振到Kondo平台的交叉，并改变p_{L,R}。我们的模型也适用于量子点干涉仪的多终端几何。本文讨论了用双缝实验测量三端结构量子点的透射相移。“我们推导出相移的测量值和本征值之间关系的解析表达式。
Entropic signatures of the single-impurity Kondo state
Stewart Blusson Quantum Matter Institute, University of British Columbia（不列颠哥伦比亚大学斯图尔特·布拉斯森量子物质研究所）；Department of Physics and Astronomy, University of British Columbia（不列颠哥伦比亚大学物理与天文学系）；Department of Physics and Astronomy, Purdue University（普渡大学物理与天文学系）；Microsoft Quantum（微软量子）
