Resonant Response of High-Temperature Superconducting Split-Ring Resonators

A study of the resonant response of high-temperature superconducting YBCO split-ring resonators (SRRs) deposited on a single crystal MgO substrate is presented. Measurement of an array of seven SRRs inside a WR-90 waveguide at temperatures below the transition temperature of YBCO (T_c ≈ 90 K) shows a stop band centered at around 8 GHz with a 1.6-GHz bandwidth, which is also seen in the full wave simulation. An individual SRR element is measured to investigate the temperature dependence of the resonance frequency and quality factor. The single SRR measurements show a small gradual shift in the transmission resonance frequency as the temperature is lowered from 90.5 to 40 K, which can be attributed to the presence of kinetic inductance. The behavior of the measured resonance frequency versus temperature is fitted to a model to study the kinetic inductance and penetration depth. The quality factor is then calculated from the measurements in the same temperature range. Finally, the permittivity and permeability are extracted from the measured scattering parameters.