Protecting SQUID metamaterials against stray magnetic field

TL;DR

This paper investigates the vulnerability of SQUID metamaterials to stray magnetic fields and proposes shielding and design improvements to preserve their resonant properties.

Contribution

It demonstrates the detrimental effects of stray magnetic fields on SQUID metamaterials and suggests practical methods to mitigate these effects.

Findings

Small magnetic fields disrupt collective resonance

Magnetic shielding reduces initial stray fields

Design improvements prevent vortex trapping

Abstract

Using superconducting quantum interference devices (SQUIDs) as basic, low-loss elements of thin-film metamaterials has one main advantage: Their resonance frequency is easily tunable by applying a weak magnetic field. The downside, however, is a strong sensitivity to stray and inhomogeneous magnetic fields. In this work, we demonstrate that even small magnetic fields from electronic components destroy the collective, resonant behaviour of the SQUID metamaterial. We also show how the effect of these fields can be minimized. As a first step, magnetic shielding decreases any initially present fields including the earth's magnetic field. However, further measures like improvements in the sample geometry have to be taken to avoid the trapping of Abrikosov vortices.