Joule heating effects in high transparency Josephson junctions

TL;DR

This paper investigates how Joule heating affects highly transparent Josephson junctions, combining theory and experiments to analyze the transition features in current-voltage characteristics and their relation to heat flow and cooling power.

Contribution

It introduces a method to determine heat flow dependence on temperature in Josephson junctions by analyzing transition voltages and excess current suppression, validated with graphene-based devices.

Findings

Cooling power scales as T_bath^3.1 near critical temperature.

Transition voltage dependence reveals heat flow characteristics.

Experimental verification with graphene junctions confirms theoretical predictions.

Abstract

We study, both theoretically and experimentally, the features on the current-voltage characteristic of a highly transparent Josephson junction caused by transition of the superconducting leads to the normal state. These features appear due to the suppression of the Andreev excess current. We show that by tracing the dependence of the voltage, at which the transition occurs, on the bath temperature and by analyzing the suppression of the excess current by the bias voltage one can recover the temperature dependence of the heat flow out of the junction. We verify theory predictions by fabricating two highly transparent superconductor-graphene-superconductor (SGS) Josephson junctions with suspended and non-suspended graphene as a non-superconducting section between Al leads. Applying the above mentioned technique we show that the cooling power of the suspended junction depends on the bath temperature as $\propto T_{\rm bath}^{3.1}$ close to the superconducting critical temperature.