Metabolometer Based on Toroidal Response

Abstract

Toroidal metamaterials stand out by extremely high-Q resonances. Their radiation losses are suppressed, and fields in the metamolecules are extremely high and sensitive to the additional losses. In this work, we introduce a novel concept of metabolometer. It is based on the combination of a microwave high-Q factor toroidal metamaterial as readout device with embedded micro-pad superconductor as an absorber of terahertz (THz) radiation. We establish that a pad with 20 kΩ/sq sheet resistance reduces metamaterial Q-factor and changes the stop-band level by as much as –50 dB at 1.5 GHz. Importantly, this sensitivity to the additional losses requires no galvanic connection to the absorber. This allows one to detect THz heating of superconducting pad via the change in metamaterial transmission spectrum. We consider the absorber as a superconducting hafnium film because of its nonlinear response at 1.5 GHz below $${{T}_{c}} = 400$$ mK. Respectively, we estimate the losses in hafnium over temperature at the metamaterial resonant frequency using Mattis–Bardeen theory. This approach can significantly improve the future design of the terahertz/millimeter-wave detectors.