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.
@article{arxiv.2201.02671,
title = {Tuning of Strong Nonlinearity in rf SQUID Meta-Atoms},
author = {Ethan Zack and Daimeng Zhang and Melissa Trepanier and Jingnan Cai and Tamin Tai and Nikos Lazarides and Johanne Hizanidis and Steven M. Anlage},
journal= {arXiv preprint arXiv:2201.02671},
year = {2022}
}