Electron refrigeration in hybrid structures with spin-split superconductors

TL;DR

This paper explores electron cooling in hybrid structures with spin-split superconductors, demonstrating improved efficiency and lower voltage operation through spin-filtering barriers and tunnel coupling.

Contribution

It introduces a novel approach to electron refrigeration using spin-split superconductors with spin-filtering barriers, enabling linear voltage dependence and enhanced cooling performance.

Findings

Cooling power exhibits a linear voltage term.

Optimal cooling occurs at lower voltages.

Efficient refrigeration achieved via tunnel coupling with regular superconductors.

Abstract

Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a non-linear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel coupling spin-split superconductors with regular ones allows for a highly efficient refrigeration of the latter.