Tunnel-Junction Thermometry Down to Millikelvin Temperatures

TL;DR

This paper introduces a simple on-chip tunnel-junction thermometer capable of measuring temperatures down to 1 millikelvin, demonstrating operation at 7 mK with a systematic thermal analysis.

Contribution

The work presents a novel, easy-to-implement thermometer based on a normal-metal–superconductor tunnel junction effective at millikelvin temperatures.

Findings

Operates reliably down to 7 mK

Thermometer's current is sensitive to the normal electrode temperature

Device design ensures thermalization to the phonon bath

Abstract

We present a simple on-chip electronic thermometer with the potential to operate down to 1 mK. It is based on transport through a single normal-metal - superconductor tunnel junction with rapidly widening leads. The current through the junction is determined by the temperature of the normal electrode that is efficiently thermalized to the phonon bath, and it is virtually insensitive to the temperature of the superconductor, even when the latter is relatively far from equilibrium. We demonstrate here the operation of the device down to 7 mK and present a systematic thermal analysis.