Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for nodeless superconducting gap in NaFe$_{1-x}$Co$_x$As from
  low-temperature thermal conductivity measurements   The thermal conductivity of optimally doped NaFe$_{0.972}$Co$_{0.028}$As
($T_c \sim$ 20 K) and overdoped NaFe$_{0.925}$Co$_{0.075}$As ($T_c \sim$ 11 K)
single crystals were measured down to 50 mK. No residual linear term
$\kappa_0/T$ is found in zero magnetic field for both compounds, which is an
evidence for nodeless superconducting gap. Applying field up to $H$ = 9 T
($\approx H_{c2}/4$) does not noticeably increase $\kappa_0/T$ in
NaFe$_{1.972}$Co$_{0.028}$As, which is consistent with multiple isotropic gaps
with similar magnitudes. The $\kappa_0/T$ of overdoped
NaFe$_{1.925}$Co$_{0.075}$As shows a relatively faster field dependence,
indicating the increase of the ratio between the magnitudes of different gaps,
or the enhancement of gap anisotropy upon increasing doping.

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The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
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The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph