Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Complex conductivity of $\rm Y_{1-x}Pr_xBa_2Cu_3O_7$ thin films measured
  by coherent terahertz spectroscopy   The complex transmission of Y_{1-x}Pr_xBa_2Cu_3O_7 single crystal thin films
has been measured in the range 0.2-1.0 THz using time domain spectroscopy. The
complex conductivity is calculated without using a Kramers-Kronig analysis. All
of the superconducting samples show a peak in $\sigma_1(T)$ below $T_c$. The
underdoped samples show a deviation from $1/(\alpha+\beta T)$ behavior above
$T_c$ that may be linked with the onset of a spin gap.

1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess