Joule heating effects in high-transparency Josephson junctions

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 nonsuspended graphene as a nonsuperconducting 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 ∝T 3.1 bath close to the superconducting critical temperature.

Thermal self-oscillations in monolayer graphene coupled to a superconducting microwave cavity

“…The parameters Σ and γ in Eq. (A2) are expected to be close to those in our recent paper [40]. There we have found ΣA ≈ 5 nW/T γ C and γ = 3.1.…”

Thermal self-oscillations in monolayer graphene coupled to a superconducting microwave cavity

“…Equation (A.3) has been verified in the experiment [50]. The parameters Σ and γ in equation (A.2) are expected to be close to those in our recent paper [51]. There we have found ΣA ≈ 5 nW/T γ C and γ = 3.1.…”

Anomalous temperature dependence of multiple Andreev reflections in a topological insulator Josephson junction

“…Here, additional features are visible outside of the induced superconducting gap whose position might be interpreted as gap features of Nb (∆ ≈ 1.3 meV). The features, however, scale in temperature qualitatively like the (smaller) induced superconducting gap and vanish at T = 1.2 K. This speaks against their assignment to a superconducting gap higher than the observed induced gap and it is more likely that they are related to heating effects in the electrodes or the lateral coplanar JJ geometry itself as suggested for similar observations in previous work on SNS JJs [6,15,37,38]. Below a temperature of T = 0.8 K, we observe additionally a small change in the differential conductance at high biases (visible in figure S2(b) by a smaller offset between 0.8 K and 0.7 K curve) corresponding to a change in differential resistance of a few Ohm.…”