Kondo-resonance, Coulomb blockade, and Andreev transport through a quantum dot

TL;DR

This paper investigates how strong Coulomb interactions influence resonant tunneling and Andreev transport in a quantum dot connected to normal and superconducting leads, revealing novel effects like Kondo-Andreev resonance and conductance suppression.

Contribution

It introduces an exact Green's function relation to analyze the interplay of Kondo effect, Coulomb blockade, and Andreev reflection in quantum dot transport.

Findings

Kondo-Andreev resonance enhances conductance at zero temperature.

Coulomb blockade suppresses Andreev reflection more than in normal leads.

Conductance varies significantly between Kondo and empty site regimes.

Abstract

We study resonant tunneling through an interacting quantum dot coupled to normal metallic and superconducting leads. We show that large Coulomb interaction gives rise to novel effects in Andreev transport. Adopting an exact relation for the Green's function, we find that at zero temperature, the linear response conductance is enhanced due to Kondo-Andreev resonance in the Kondo limit, while it is suppressed in the empty site limit. In the Coulomb blockaded region, on the other hand, the conductance is reduced more than the corresponding conductance with normal leads because large charging energy suppresses Andreev reflection.