Electron transport through strongly interacting quantum dot coupled to normal metal and superconductor

TL;DR

This paper investigates electron transport in a quantum dot system coupled to a normal metal and superconductor, focusing on the interplay of Kondo effect and Andreev scattering, revealing suppression of Andreev conductance and absence of zero-bias anomaly.

Contribution

It introduces a combined theoretical approach using equation of motion and slave boson methods to analyze transport in strongly interacting quantum dots with superconductor coupling.

Findings

Andreev conductance is strongly suppressed

No zero-bias Kondo anomaly observed

Particle-hole and coupling asymmetries significantly affect transport

Abstract

We study the electron transport through the quantum dot coupled to the normal metal and BCS-like superconductor (N - QD - S) in the presence of the Kondo effect and Andreev scattering. The system is described by the single impurity Anderson model in the limit of strong on-dot interaction. We use recently proposed equation of motion technique for Keldysh nonequilibrium Green's function together with the modified slave boson approach to study the electron transport. We derive formula for the current which contains various tunneling processes and apply it to study the transport through the system. We find that the Andreev conductance is strongly suppressed and there is no zero-bias (Kondo) anomaly in the differential conductance. We discuss effects of the particle-hole asymmetry in the electrodes as well as the asymmetry in the couplings.