Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconducting properties of Fe-based layered superconductor
  LaO$_{0.9}$F$_{0.1-\delta}$FeAs   We have employed a new route to synthesize single phase F-doped LaOFeAs
compound and confirmed the superconductivity above 20 K in this Fe-based
system. We show that the new superconductor has a rather high upper critical
field of about 54 T. A clear signature of superconducting gap opening below
T$_c$ was observed in the far-infrared reflectance spectra, with
2$\Delta/\textit{k}T_c\approx$3.5-4.2. Furthermore, we show that the new
superconductor has electron-type conducting carrier with a rather low carrier
density.

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The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess