Kondo physics in double quantum dot based Cooper pair splitters

TL;DR

This paper investigates how superconducting pairing affects Kondo phenomena in double quantum dot Cooper pair splitters, revealing suppression and crossover behaviors in different Kondo regimes through advanced numerical methods.

Contribution

It provides a detailed theoretical analysis of the interplay between superconductivity and Kondo effects in double quantum dot systems, highlighting regime crossovers and suppression mechanisms.

Findings

Superconducting pairing suppresses the SU(2) Kondo effect.

A crossover from SU(4) to SU(2) Kondo state occurs with increased coupling.

The study uses density-matrix numerical renormalization group method.

Abstract

The Andreev transport properties of double quantum dot based Cooper pair splitters with one superconducting and two normal leads are studied theoretically in the Kondo regime. The influence of the superconducting pairing correlations on the local density of states, Andreev transmission coefficient and Cooper pair splitting efficiency is thoroughly analyzed. It is shown that finite superconducting pairing potential quickly suppresses the SU(2) Kondo effect, which can however reemerge for relatively large values of coupling to superconductor. In the SU(4) Kondo regime, a crossover from the SU(4) to the SU(2) Kondo state is found as the coupling to superconductor is enhanced. The analysis is performed by means of the density-matrix numerical renormalization group method.