Andreev reflection and the Kondo effect in side-coupled double quantum dots

Abstract

We study the transport due to the Andreev reflection through side-coupled double quantum dots, using the numerical renormalization group (NRG). We find that superconducting interference via the side dot is suppressed as increasing the Coulomb interaction, and the conductance in the Kondo regime is enhanced. This behavior stands in stark contrast to the normal conductance, in which a wide valley is seen in the Kondo regime. It is further elucidated that two separate Fano structures appear in the gate-voltage dependence of the Andreev transport, where a single plateau appears in the normal transport.