Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Signature of multigap nodeless superconductivity in fluorine-doped
  NdFeAsO   We investigate the temperature dependence of the lower critical field
$H_{c1}(T)$, the field at which vortices penetrate into the sample, of a
high-quality fluorine-doped NdFeAsO single crystal under static magnetic fields
$H$ parallel to the $c$-axis. The temperature dependence of the first vortex
penetration field has been experimentally obtained and pronounced changes of
the $H_{c1}$(T) curvature are observed, which is attributed to the multiband
superconductivity. Using a two-band model with $s$-wave-like gaps, the
temperature-dependence of the lower critical field $H_{c1}(T)$ can be well
described. These observations clearly show that the superconducting energy gap
in fluorine-doped NdFeAsO is nodeless. The values of the penetration depth at
$T$ = 0\,K have been determined and confirm that the pnictide superconductors
obey an Uemura-style relationship between $T_{c}$ and $\lambda_{ab}(0)^{-2}$

3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int