Superconducting metamaterials

Evanescent wave amplification has been predicted under the ideal condition that the index of refraction, n=−1+i0 precisely, but is difficult to observe in practice because current metamaterials suffer from high losses. We present experimental results on a metamaterial that employs superconducting Nb metals and low-loss dielectric materials. Results include transmission data on a wire, split-ring resonator, and a combination medium at temperatures between 4.2 and 297K. Evidence of negative effective permittivity, permeability, and a negative effective index passband are seen in the superconducting state between 50MHz and 18GHz. We find a dielectric loss of εeff,2=2.6×10−3 in a superconducting wire array at 10.75GHz.