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Josephson Current in Strongly Correlated Double Quantum Dots

Zitko,Rok; Lee, Minchul; López, Rosa; Aguado, Ramón;Choi,Mahn-Soo;
Physical Review Letters 105, 116803 (2010)

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/TK 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∼TK), there appears an island of π′ phase at large values of the superconducting phase difference.