High efficiency superconducting diode effect in a gate-tunable double-loop SQUID

TL;DR

This paper demonstrates a highly efficient superconducting diode effect in a double-loop SQUID with gate-tunable Josephson junctions, achieving over 50% diode efficiency through independent control of current-phase relationships.

Contribution

It introduces a double-loop SQUID with gate-tunable junctions enabling independent control of harmonic content and amplitude of CPRs, significantly enhancing diode efficiency.

Findings

Diode efficiency exceeding 50% achieved.

Flux oscillations match a simple SQUID model.

Independent control of harmonic content demonstrated.

Abstract

In superconducting quantum interference devices (SQUIDs), the superconducting diode effect may be generated by interference of multiple harmonic components in the current-phase relationships (CPRs) of different branches forming SQUID loops. Through the inclusion of two gate-tunable Josephson junctions in series in each interference branch of a double-loop SQUID, we demonstrate independent control over both the harmonic content and the amplitude of three interfering CPRs, facilitating significant improvement in the maximum diode efficiency. Through optimized gate-controlled tuning of individual Josephson energies, diode efficiency exceeding 50% is demonstrated. Flux-dependent oscillations show quantitative agreement with a simple model of SQUID operation.