Superconducting Metamaterials
  Evanescent wave amplification has been predicted under the ideal condition n = -1 + i 0 precisely, in the absence of retardation effects, but is difficult to observe in practice because current metamaterial designs suffer from high losses. We present results on a new metamaterial design that employs superconducting Niobium metals and low-loss dielectric materials to reduce the losses. We present transmission data on a wire medium, a split-ring resonator medium, and a combination of the two at temperatures between 4.2 K and room temperature. Evidence of negative effective permittivity, permeability, and a negative effective index passband are seen in the superconducting state between 50 MHz and 18 GHz. We find a dielectric loss of \epsilon_{eff,2} = 3 x 10^{-3} in a superconducting wire array at 10.75 GHz. 
Michael Ricci, Nathan Orloff and Steven M. Anlage