Hamiltonian approach to the charge transfer statistics of Kondo quantum dots contacted by a normal metal and a superconductor

TL;DR

This paper develops a Hamiltonian-based method to analyze the full counting statistics of charge transfer in Kondo quantum dots connected to normal and superconducting leads, predicting noise and cross-correlation behaviors.

Contribution

It introduces a novel Hamiltonian approach to calculate FCS in Kondo quantum dots with superconducting contacts, validated against experimental data.

Findings

Positive cross-correlation can occur with a superconductor and two normal leads.

The method effectively handles weak coupling to superconductors with large gaps.

Predictions include noise characteristics and cross-correlation in Kondo regimes.

Abstract

We analyze the full counting statistics (FCS) of quantum dots in the Kondo regime contacted by normal and superconducting leads or an STM tip. To describe the Kondo resonance we use an effective model for the quantum dot in the Kondo regime in combination with the FCS for tunneling contacts calculated using the Hamiltonian approach. We show that the situation of weak coupling to the superconducting electrode in the case of superconductor gap being larger than the Kondo resonance width can be easily handled and verify the method by comparing our theoretical predictions to experimental data. This allows us to make predictions for the noise and cross-correlation in setups involving a superconductor. We find that a positive cross-correlation is possible in the case of a superconductor and two normal leads contacted via two quantum dots in the Kondo regime.