On-chip magnetic cooling of a nanoelectronic device

TL;DR

This paper demonstrates on-chip magnetic cooling of electrons in a nanostructure, achieving temperatures below 5 mK for over 1000 seconds by coupling electrons directly to refrigerated nuclei, surpassing traditional cooling methods.

Contribution

It introduces a novel on-chip magnetic cooling technique that overcomes electron-phonon coupling limitations, enabling ultra-low electron temperatures in nanostructures.

Findings

Electrons cooled from 9 mK to below 5 mK

Cooling duration exceeds 1000 seconds

Method applicable to various nanostructures

Abstract

We demonstrate significant cooling of electrons in a nanostructure below 10 mK by demagnetisation of thin-film copper on a silicon chip. Our approach overcomes the typical bottleneck of weak electron-phonon scattering by coupling the electrons directly to a bath of refrigerated nuclei, rather than cooling via phonons in the host lattice. Consequently, weak electron-phonon scattering becomes an advantage. It allows the electrons to be cooled for an experimentally useful period of time to temperatures colder than the dilution refrigerator platform, the incoming electrical connections, and the host lattice. There are efforts worldwide to reach sub-millikelvin electron temperatures in nanostructures to study coherent electronic phenomena and improve the operation of nanoelectronic devices. On-chip magnetic cooling is a promising approach to meet this challenge. The method can be used to reach low, local electron temperatures in other nanostructures, obviating the need to adapt traditional, large demagnetisation stages. We demonstrate the technique by applying it to a nanoelectronic primary thermometer that measures its internal electron temperature. Using an optimised demagnetisation process, we demonstrate cooling of the on-chip electrons from 9 mK to below 5 mK for over 1000 seconds.