On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK

TL;DR

This paper demonstrates a method to cool nanoelectronic devices to 2.8 mK using adiabatic demagnetization of both leads and metallic islands in a Coulomb blockade thermometer, addressing heat leaks and vibrations.

Contribution

It introduces a novel on-chip cooling technique combining demagnetization of leads and islands to achieve ultra-low temperatures in nanoelectronics.

Findings

Achieved thermometer cooling down to 2.8 mK.

Identified pulse tube vibrations as main heating source.

Thermal model supports experimental results.

Abstract

Cooling nanoelectronic devices below 10 mK is a great challenge since thermal conductivities become very small, thus creating a pronounced sensitivity to heat leaks. Here, we overcome these difficulties by using adiabatic demagnetization of \emph{both} the electronic leads \emph{and} the large metallic islands of a Coulomb blockade thermometer. This reduces the external heat leak through the leads and also provides on-chip refrigeration, together cooling the thermometer down to 2.8$\pm$0.1 mK. We present a thermal model which gives a good qualitative account and suggests that the main limitation is heating due to pulse tube vibrations. With better decoupling, temperatures below 1 mK should be within reach, thus opening the door for microkelvin nanoelectronics.