Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Intrinsic left-handed electromagnetic properties in anisotropic
  superconductors   Left-handed materials usually are realized in artificial subwavelength
structures. Here we show that some anisotropic superconductors, such as
$\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}}$, $\mathrm{YBa_2Cu_xO_y}$ and
$\mathrm{La_{2-x}Sr_xCuO_4}$, are intrinsic left-handed materials. The
condition is that the plasma frequency in the $c$ axis, $\omega_c$, and in the
$ab$ plane, $\omega_{ab}$, and the operating frequency, $\omega$, satisfy
$\omega_c<\omega<\omega_{ab}$. In addition $\omega$ should be smaller than the
superconducting energy gap to sustain superconductivity. We study the
reflection and transmission of electromagnetic waves, and reveal negative
refraction and backward wave with phase velocity opposite to the direction of
energy flux propagation. We also discuss possible approaches of improvement,
making these properties feasible for experimental validation. Being intrinsic
left-hand materials, the anisotropic superconductors are promising for
applications in novel electromagnetic devices in the terahertz frequency band.

12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs