Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
Phys Rev Lett. 2012 Jun 1;108(22):227001. doi: 10.1103/PhysRevLett.108.227001. Epub 2012 May 30.
We study the Josephson current 0-π transition of a quantum dot tuned to the Kondo regime. The physics can be quantitatively captured by the numerically exact continuous time quantum Monte Carlo method applied to the single-impurity Anderson model with Bardeen-Cooper-Schrieffer superconducting leads. For a comparison to an experiment, the tunnel couplings are determined by fitting the normal-state linear conductance. Excellent agreement for the dependence of the critical Josephson current on the level energy is achieved. For increased tunnel couplings the Kondo scale becomes comparable to the superconducting gap, and the regime of the strongest competition between superconductivity and Kondo correlations is reached; we predict the gate voltage dependence of the critical current in this regime.
我们研究了调谐到近藤 regime 的量子点的约瑟夫森电流 0-π 转变。通过应用于带有 Bardeen-Cooper-Schrieffer 超导引线的单杂质 Anderson 模型的数值精确连续时间量子 Monte Carlo 方法，可以定量地捕获物理现象。为了与实验进行比较，通过拟合正常状态线性电导来确定隧道耦合。对于临界约瑟夫森电流对能级能量的依赖性，实现了极好的一致性。随着隧道耦合的增加，近藤标度变得与超导能隙相当，达到了超导性和近藤相关性之间最强竞争的 regime；我们预测了这个 regime 中临界电流的栅极电压依赖性。
