Low Temperature Characteristics of the Metal-Superconductor NIS Tunneling Thermometer

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

Automated summary

In this technical note, the temperature dependence and saturation phenomenon of tunnel junctions between a superconductor and a normal metal (NIS junction) are reanalyzed, and it is shown that the quantitatively low temperature behavior can be explained by the temperature independent subgap current of the junction alone in some cases.