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 $297\mathrm{K}$ . Evidence of negative effective permittivity, permeability, and a negative effective index passband are seen in the superconducting state between $50\mathrm{MHz}$ and $18\mathrm{GHz}$ . We find a dielectric loss of ${\epsilon }_{\mathrm{eff},2}=2.6\times {10}^{-3}$ in a superconducting wire array at $10.75\mathrm{GHz}$ .