Flux-tunable barrier in proximity Josephson junctions

TL;DR

This paper demonstrates how a micron-scale normal metal loop with superconducting contacts can have its thermal activation barrier fully modulated by magnetic flux, advancing control in quantum interference devices.

Contribution

It extends the Ambegaokar-Halperin model to proximity junctions with flux-tunable coupling energy, providing new insights into thermal fluctuations in such systems.

Findings

Barrier modulation fits the extended Ambegaokar-Halperin model with a constant factor

Thermal activation barrier can be fully controlled by magnetic flux

Potential for enhanced control in quantum interference devices

Abstract

We report experiments on micron-scale normal metal loop connected by superconducting wires, where the sample geometry enables full modulation of the thermal activation barrier with applied magnetic flux, resembling a symmetric quantum interference device. We find that except a constant factor of five, the modulation of the barrier can be well fitted by the Ambegaokar-Halperin model for a resistively shunted junction, extended here to a proximity junction with flux-tunable coupling energy estimated using quasiclassical theory. This observation sheds light on the understanding of effect of thermal fluctuation in proximity junctions, while may also lead to an unprecedented level of control in quantum interference devices.