Competition between electronic cooling and Andreev dissipation in a superconducting micro-cooler

TL;DR

This paper investigates the competition between electronic cooling and Andreev dissipation in superconducting micro-coolers, analyzing how phase coherence and junction transparency affect electron temperature at very low temperatures.

Contribution

It provides a detailed thermal model that incorporates Andreev current effects, highlighting the crossover between quasi-particle and phase-coherent currents in micro-coolers.

Findings

Identification of the crossover between single quasi-particle and Andreev currents.

Quantitative analysis of how phase-coherence length influences electron cooling.

Demonstration of the impact of junction transparency on thermal behavior.

Abstract

We discuss very low temperature experiments on superconducting micro-coolers made of a double Normal metal - Insulator - Superconductor junction. We investigate with a high resolution the differential conductance of the micro-cooler as well as of additional probe junctions. There is an explicit crossover between the single quasi-particle current and the phase-coherent Andreev current. We establish a thermal model by considering the thermal contribution due to the Andreev current. The related increase of the electron temperature is discussed, including the influence of several parameters like the phase-coherence length or the tunnel junction transparency.