Superconducting RF Metamaterials Made with Magnetically Active Planar Spirals
Superconducting metamaterials combine the advantages of low-loss, large inductance (with the addition of kinetic inductance), and extreme tunability compared to their normal metal counterparts. Therefore, they allow realization of compact designs operating at lowfrequencies.We have recently developed radio frequency (RF) metamaterials with a high loaded quality factor and an electrical size as small as ~ λ/658 (λ is the free space wavelength) by using Nb thin films. The RF metamaterial is composed of truly planar spirals patterned with lithographic techniques. Linear transmission characteristics of these metamaterials show robust Lorentzian resonant peaks in the sub-100 MHz frequency range below the Tc of Nb. Though Nb is a non-magnetic material, the circulating currents in the spirals generated by RF signals produce a strong magnetic response, which can be tuned sensitively either by temperature or magnetic field thanks to the superconducting nature of the design. We have also observed strong nonlinearity and meta-stable jumps in the transmission data with increasing RF input power until the Nb is driven into the normal state. We discuss the factors modifying the induced magnetic response from single and 1-D arrays of spirals in the light of numerical simulations.
C. Kurter et al., "Superconducting RF Metamaterials Made with Magnetically Active Planar Spirals," IEEE Transactions on Applied Superconductivity, vol. 21, no. 3 PART 1, pp. 709-712, Institute of Electrical and Electronics Engineers (IEEE), Jun 2011.
The definitive version is available at https://doi.org/10.1109/TASC.2010.2088093
Keywords and Phrases
Circulating current; Compact designs; Free-space wavelengths; Frequency ranges; Input power; Kinetic inductances; Linear transmission; Loaded quality factor; Low loss; Magnetic response; Meta-stable; Non-magnetic materials; Normal metals; Normal state; Numerical simulation; Planar spirals; Radio frequencies; Resonant peaks; RF metamaterials; RF signal; Strong nonlinearity; Transmission data; Tunabilities; Electronic equipment; Inductance; Lithography; Magnetic fields; Magnetic materials; Niobium; Superconductivity; Metamaterials
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