Josephson current through a Kondo molecule

TL;DR

This paper studies how the Josephson current flows through a double quantum dot in the Kondo regime with superconducting leads, revealing how different configurations and coupling ratios control supercurrent behavior.

Contribution

It provides a non-perturbative analysis of the Josephson current in DQDs in the Kondo regime, highlighting configuration-dependent differences in supercurrent modulation.

Findings

Critical current decreases with t/Γ in parallel configuration.

Critical current peaks at t/Γ=1 in series configuration.

Supercurrent flow can be controlled by tuning t/Γ ratio.

Abstract

We investigate transport of Cooper pairs through a double quantum dot (DQD) in the Kondo regime and coupled to superconducting leads. Within the non-perturbative slave boson mean-field theory we evaluate the Josephson current for two different configurations, the DQD coupled in parallel and in series to the leads. We find striking differences between these configurations in the supercurrent as a function of the ratio t/\Gamma, where t is the interdot coupling and \Gamma is the coupling to the leads: the critical current I_c decreases monotonously with t/\Gamma for the parallel configuration whereas I_c exhibits a maximum at t/\Gamma=1 in the serial case. These results demonstrate that a variation of the ratio t/\Gamma enables to control the flow of supercurrent through the Kondo resonance of the DQD.