Title: Coherent Oscillations of Driven rf SQUID Metamaterials,
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.