Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical and Hidden Transport Properties of
  BaFe$_{1.91}$Ni$_{0.09}$As$_{2}$ Film   Optical spectroscopy was used to study the electrodynamics and hidden
transport properties of a BaFe$_{1.91}$Ni$_{0.09}$As$_{2}$ thin superconducting
film. We analyzed the normal state data using a Drude-Lorentz model with two
Drude components: one narrow ($D_1$) and another broad one ($D_2$). In the
superconducting state, two gaps with $2\Delta _{0}^{(2)}/k_BT_c=1.9$--2.0 and
$2\Delta _{0}^{(1)}/k_BT_c=4.0$--4.3 are formed from the narrow component $D_1$
while the broad component $D_2$ remains ungapped. The calculated total DC
resistivity of the film and the low-temperature scattering rate for the narrow
Drude component show a hidden Fermi-liquid behavior. The change of total
electron-boson coupling ($\lambda_{tot}$) and representative energy
($\Omega_{0}$) in the normal state with respect to the superconducting state is
typical of other iron-based materials as well as high-temperature
superconducting (HTSC) cuprates.

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The categories of this paper are: hep-ph
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ