Reversibility of superconducting nb weak links driven by the proximity effect in a quantum interference device

Area of Science:

• Condensed Matter Physics
• Superconductivity
• Quantum Devices

Background:

• Superconducting constrictions exhibit thermal hysteresis, affecting their transport characteristics.
• Understanding thermal regimes is crucial for controlling junction behavior.

Purpose of the Study:

• To demonstrate the role of the proximity effect in thermal hysteresis.
• To analyze thermal instabilities in superconducting constrictions.

Main Methods:

• Analysis of transport characteristics in micron-size superconducting quantum interference devices (SQUIDs).
• Controlled geometry experiments to observe successive thermal instabilities.

Main Results:

• A complete picture of different thermal regimes determining junction hysteresis was obtained.
• Below the critical temperature, critical current behavior shifts from weak-link to proximity-effect-driven.
• Proximity effect results in a small, robust critical current amplitude, preventing hysteresis.

Conclusions:

• The proximity effect plays a key role in the thermal hysteresis of superconducting constrictions.
• The observed nonhysteretic behavior is attributed to the proximity effect's influence on critical current robustness.