Miniaturized Superconducting Metamaterials for Radio Frequencies

We have developed a low-loss, ultra-small radio frequency $(RF)$ metamaterial operating at $\sim$76 MHz. This miniaturized medium is made up of planar spiral elements with diameter as small as $\sim$$\lambda$/658 ($\lambda$ is the free space wavelength), fashioned from Nb thin films on quartz substrates. The transmission data are examined below and above the superconducting transition temperature of Nb for both a single spiral and a one dimensional array. The validity of the design is tested through numerical simulations and good agreement is found. We discuss how superconductors enable such a compact design in the $RF$ with high loaded-quality factor (in excess of 5000), which is in fact difficult to realize with ordinary metals.