Hybrid quantum dot–superconducting systems: Josephson current and Kondo effect in the narrow-band limit

The case of a quantum dot connected to two superconducting leads is studied by using the narrow-band limit to describe the superconducting degrees of freedom. The model provides a simple theoretical framework, almost analytical, to analyze the interplay between the Kondo effect, superconductivity, a...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2015-01, Vol.91 (4), Article 045442
Main Authors: Allub, R., Proetto, C. R.
Format: Article
Language:English
Subjects:
Condensed matter
Degrees of freedom
Hybrid systems
Kondo effect
Mathematical analysis
Mathematical models
Qunatum dots
Superconductivity
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Summary:The case of a quantum dot connected to two superconducting leads is studied by using the narrow-band limit to describe the superconducting degrees of freedom. The model provides a simple theoretical framework, almost analytical, to analyze the interplay between the Kondo effect, superconductivity, and finite temperature. The model allows us to calculate, at any temperature T, the equilibrium Josephson current through the dot in a very straightforward way as a function of Delta /J. The behavior of the current allows us to distinguish the four types of hybrid junctions: 0, 0', [pi], and [pi]. The presence of the 0- and 0'-junction configurations are intrinsically linked to the Kondo effect in the quantum dot, while the [pi]- and [pi]' junction configurations are driven by the superconductivity in the leads. The results, obtained with a minimum of numerical effort, are in a good qualitative agreement with more demanding calculational approaches aimed to solve the full model.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.91.045442