Josephson junction based thermometer and its application in bolometry

TL;DR

This paper introduces a novel Josephson junction-based thermometer utilizing an SIS'IS structure, demonstrating high temperature sensitivity and potential advantages over traditional transition edge sensors for bolometry applications.

Contribution

The paper presents a new SIS'IS-based transition edge sensor with enhanced tunability and sensitivity, overcoming size limitations of conventional sensors.

Findings

Temperature sensitivity of 2 μK/√Hz demonstrated.

Estimated NEP of 4×10⁻¹⁷ W/√Hz at 313 mK.

Device allows wide-range input resistance tuning.

Abstract

We propose a new type of a transition edge sensor based on an Al/AlOx/Ti/AlOx/Al superconductor - insulator - superconductor - insulator - superconductor (SIS'IS) structure. It exhibits sharp dependence of zero bias resistance on temperature of the titanium absorber in the vicinity of its superconducting critical temperature. We demonstrate temperature sensitivity of the device to be $2\ \mu \text{K}/\sqrt{\text{Hz}}$. Noise Equivalent Power (NEP) of the device, limited by the amplifier noise, is estimated to be $4\times 10^{-17}\ {\rm W}/ \sqrt{\rm Hz}$ at 313 mK. The tunnel junctions between superconducting leads should help to overcome the size limitation imposed by proximity effect in conventional transition edge sensors, without sacrificing the sensitivity. Besides that, the input resistance of the device can be tuned in a wide range.