J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
Phys Rev Lett. 2010 Sep 10;105(11):116803. doi: 10.1103/PhysRevLett.105.116803. Epub 2010 Sep 8.
We study the Josephson current through a serial double quantum dot and the associated 0-π transitions which result from the subtle interplay between the superconductivity, the Kondo physics, and the interdot superexchange interaction. The competition between them is examined by tuning the relative strength Δ/T(K) of the superconducting gap and the Kondo temperature, for different strengths of the superexchange coupling determined by the interdot tunneling t relative to the level broadening Γ. We find strong renormalization of t, a significant role of the superexchange coupling J, and a rich phase diagram of the 0 and π-junction regimes. In particular, when both the superconductivity and the exchange interaction compete with the Kondo physics (Δ∼J∼T(K)), there appears an island of π' phase at large values of the superconducting phase difference.
我们研究了通过串联双量子点的约瑟夫森电流以及由于超导性、Kondo 物理和双点间超交换相互作用之间的微妙相互作用而产生的相关 0-π 跃迁。通过调节超导能隙和 Kondo 温度的相对强度Δ/T(K)，以及由双点间隧道 t 相对于能级展宽Γ确定的超交换耦合的不同强度，研究了它们之间的竞争。我们发现 t 的强烈重整化、超交换耦合 J 的重要作用以及 0 和π 结区的丰富相图。特别是，当超导性和交换相互作用都与 Kondo 物理（Δ∼J∼T(K)）竞争时，在超导相位差较大的值处出现π'相的岛屿。
