MicroSQUIDs based on V/Cu/V Josephson nanojunctions

TL;DR

This paper presents the development and characterization of microSQUID devices using nanoscale V/Cu/V Josephson junctions, demonstrating promising magnetic flux resolution and potential for further noise performance improvements.

Contribution

It introduces a novel fabrication of microSQUIDs with V/Cu/V Josephson junctions and provides detailed characterization of their quantum interference and flux sensitivity.

Findings

Achieved flux-to-voltage transfer functions up to 450 microV/Phi_0

Demonstrated flux resolution below 3 microPhi_0/Hz^{1/2}

Performance comparable to state-of-the-art commercial SQUIDs

Abstract

We report on the fabrication and characterization of microSQUID devices based on nanoscale vanadium/copper/vanadium Josephson weak links. Magnetically driven quantum interference patterns have been measured for temperatures in the 0.24 - 2 K range. As magnetometers, these devices obtain flux-to-voltage transfer function values as high as 450 microV/Phi_0 leading to promising magnetic flux resolution Phi_N < 3 microPhi_0 / Hz^(1/2), being here limited by the room temperature preamplification stage. Significant improvements in the flux noise performance figures, which are already competitive with existing state-of-the-art commercial SQUIDs systems, are expected either with cryogenic preamplification or with the adoption of optimized electronic readout stages based on active feedback schemes.