Thermoelectric transport through a quantum dot coupled to a normal metal and BCS superconductor

TL;DR

This paper explores how a quantum dot connected to a normal metal and a superconductor exhibits altered thermoelectric properties due to superconductivity, Kondo effect, and Andreev scattering, revealing non-Fermi liquid behavior.

Contribution

It provides new insights into the impact of superconductivity and Coulomb interactions on thermoelectric transport in quantum dots, highlighting deviations from Fermi liquid theory.

Findings

Thermopower is significantly enhanced near the superconducting transition.

Andreev reflections are suppressed by strong Coulomb repulsion.

The system violates Wiedemann-Franz law indicating non-Fermi liquid ground state.

Abstract

I discuss thermoelectric properties of a quantum dot coupled to one normal and one superconducting lead in the presence of Kondo effect and Andreev scattering. I will focus on conductance, thermal conductance, thermopower and related quantities like thermoelectric figure of merit which is a direct measure of the usefulness of the system for applications and Wiedemann-Franz ratio which indicates if the system is in the Fermi liquid state. I will show that the superconductivity strongly modifies the thermal properties of the system. In particular, the thermopower is strongly enhanced near the superconducting transition temperature. Moreover, the Andreev reflections are suppressed due to strong on-dot Coulomb repulsion. The suppression of the Andreev reflections leads to a violation of the Wiedemann-Franz law and to a non-Fermi liquid ground state.