Tuning of Strong Nonlinearity in rf SQUID Meta-Atoms

TL;DR

This paper investigates the nonlinear behavior of rf-SQUID meta-atoms through intermodulation measurements, revealing flux-tunable gaps and chaos, with implications for microwave amplification and tunable filters.

Contribution

It introduces a comprehensive analysis combining experimental measurements and theoretical modeling to understand nonlinear dynamics and chaos in rf-SQUID meta-atoms.

Findings

Flux-tunable IM response gaps

Enhanced IM near geometric resonance

Prediction of chaos in narrow regimes

Abstract

Strong nonlinearity of a self-resonant radio frequency superconducting quantum interference device (rf-SQUID) meta-atom is explored via intermodulation (IM) measurements. Previous work in zero dc magnetic flux showed a sharp onset of IM response as the frequency sweeps through the resonance. A second onset at higher frequency was also observed, creating a prominent gap in the IM response. By extending those measurements to nonzero dc flux, new dynamics are revealed, including: dc flux tunabililty of the aforementioned gaps, and enhanced IM response near geometric resonance of the rf-SQUID. These features observed experimentally are understood and analyzed theoretically through a combination of a steady state analytical modeling, and a full numerical treatment of the rf SQUID dynamics. The latter, in addition, predicts the presence of chaos in narrow parameter regimes. The understanding of intermodulation in rf-SQUID metamaterials is important for producing low-noise amplification of microwave signals and tunable filters.