Temperature-biased double-loop Josephson flux transducer

TL;DR

This paper presents a theoretical analysis of a thermally-biased Josephson junction device with two superconducting loops, demonstrating a magnetically controllable step-like critical current response suitable for sensitive flux transduction.

Contribution

It introduces a novel design of a double-loop Josephson flux transducer with independent flux control, showing high sensitivity and controllability of the critical current response.

Findings

Demonstrates a magnetically controllable step-like critical current response.

Shows high transfer function sensitivity to magnetic flux changes.

Validates the device's potential as a sensitive flux transducer.

Abstract

We theoretically study the behavior of the critical current of a thermally-biased tunnel Josephson junction with a particular design, in which the electrodes of the junction are enclosed in two different superconducting loops pierced by independent magnetic fluxes. In this setup, the superconducting gaps can be modified independently through the magnetic fluxes threading the loops. We investigate the response of the device as a function of the magnetic fluxes, by changing the asymmetry parameter, i.e., the ratio between the zero-temperature superconducting gaps $\delta=\Delta_{10}/\Delta_{20}$, and the temperatures of the two rings. We demonstrate a magnetically controllable step-like response of the critical current, which emerges even in a symmetric junction, $\delta=1$. Finally, we discuss the optimal working conditions and the high response of the critical current to small changes in the magnetic flux, reporting good performances of the transducer, with a high transfer function that depends on the operating point and the quality of the junction.