Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph