2004/06/30 by Akira Oguri, Yoshihide Tanaka, A. C. Hewson · 1 citation
Physics and Astronomy · #Anderson impurity model #Asymmetry #Condensed matter physics #Coupling (piping) #Ground state #Impurity #Inverse #Josephson effect #Kondo effect #Magnetic moment #Phase transition #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum mechanics #Quantum phase transition #Superconductivity #Topological Materials and Phenomena #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1143/jpsj.73.2494
published as J. Phys. Soc. Jpn. 73, 2494 (2004) · 23 pages, 13 figures, typos are corrected
openalex publication_date 2004/09/15 · arxiv created 2004/12/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We propose a minimal model for the Josephson current through a quantum dot in a Kondo regime. We start with the model that consists of an Anderson impurity connected to two superconducting (SC) leads with the gaps Δα=|Δα| e^i θα, where α = L, R for the lead at left and right. We show that, when one of the SC gaps is much larger than the others |ΔL| ≫ |ΔR|, the starting model can be mapped exactly onto the single-channel model, which consists of the right lead of ΔR and the Anderson impurity with an extra onsite SC gap of Δd ≡ ΓL ei θL. Here θL and ΓL are defined with respect to the starting model, and ΓL is the level width due to the coupling with the left lead. Based on this simplified model, we study the ground-state properties for the asymmetric gap, |ΔL| ≫ |ΔR|, using the numerical renormalization group (NRG) method. The results show that the phase difference of the SC gaps φ ≡ θR -θL, which induces the Josephson current, disturbs the screening of the local moment to destabilize the singlet ground state typical of the Kondo system. It can also drive the quantum phase transition to a magnetic doublet ground state, and at the critical point the Josephson current shows a discontinuous change. The asymmetry of the two SC gaps causes a re-entrant magnetic phase, in which the in-gap bound state lies close to the Fermi level.