# Coherent Oscillations of Driven rf SQUID Metamaterials

## TL;DR

This paper investigates the nonlinear and tunable electromagnetic behavior of rf SQUID metamaterials, emphasizing the importance of coherence among SQUIDs and methods to restore it under disorder.

## Contribution

It provides experimental and numerical insights into coherence loss mechanisms and demonstrates techniques to recover coherence in rf SQUID metamaterials.

## Key findings

- Coherence is mainly disrupted by a dc flux gradient.
- Increasing temperature or rf flux amplitude can restore coherence.
- Methods to enhance coherence improve metamaterial performance.

## Abstract

Through experiments and numerical simulations we explore the behavior of rf SQUID (radio frequency superconducting quantum interference device) metamaterials, which show extreme tunability and nonlinearity. The emergent electromagnetic properties of this metamaterial are sensitive to the degree of coherent response of the driven interacting SQUIDs. Coherence suffers in the presence of disorder, which is experimentally found to be mainly due to a dc flux gradient. We demonstrate methods to recover the coherence, specifically by varying the coupling between the SQUID meta-atoms and increasing the temperature or the amplitude of the applied rf flux.