Reversibility of Superconducting Nb Weak Links Driven by the Proximity Effect in a Quantum Interference Device

TL;DR

This paper investigates how the proximity effect influences the thermal hysteresis in superconducting Nb weak links within quantum interference devices, revealing conditions for reversible behavior driven by thermal regimes.

Contribution

It provides a detailed analysis of thermal instabilities and identifies how proximity effect transitions the junctions from hysteretic to non-hysteretic states in superconducting quantum interference devices.

Findings

Proximity effect reduces thermal hysteresis in Nb weak links.

Thermal regimes determine hysteretic or non-hysteretic behavior.

Critical current behavior shifts from classical weak-link to proximity-driven regime.

Abstract

We demonstrate the role of proximity effect in the thermal hysteresis of superconducting constrictions. From the analysis of successive thermal instabilities in the transport characteristics of micron-size superconducting quantum interference devices with a well-controlled geometry, we obtain a complete picture of the different thermal regimes. These determine whether the junctions are hysteretic or not. Below the superconductor critical temperature, the critical current switches from a classical weak-link behavior to one driven by the proximity effect. The associated small amplitude of the critical current makes it robust with respect to the heat generation by phase-slips, leading to a non-hysteretic behavior.