Chaos and Chimera in Hysteretic RF SQUID Metamaterials*

RF SQUIDs have been established as viable building blocks for microwave frequency metamaterials [1,2]. The RF SQUID resonance is tunable under applied DC flux, with upper-frequency range scaling as √(1+β_rf). Our previous design restricted the parameter β_rf below unity to avoid hysteresis, thus limited the resonance range. We have built new arrays of RF SQUID meta-atoms in the hysteretic regime to explore their interesting properties with the ultimate goal of extending the resonance frequency tunability. In particular, a strong and positive out-of-plane coupling among the SQUIDs is achieved through an alternating-overlapping-loop geometry, potentially mitigating the hysteresis from high-β_rf SQUID meta-atoms. Much theoretical work has predicted chaotic dynamics and chimera states in such systems. Observations of the above nonlinear phenomena in microwave transmission measurements and laser scanning microscopy [3] will be reported.

[1] Phys. Rev. X, 3, 041029 (2013) https://doi.org/10.1103/PhysRevX.3.041029
[2] Phys. Rev. X, 5, 041045 (2015) https://doi.org/10.1103/PhysRevX.5.041045
[3] Appl. Phys. Lett. 114, 082601 (2019) https://doi.org/10.1063/1.5064658