Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconductivity in layered iron Selenide induced by cobalt- and
  sodium-doping   Superconductivity with zero resistance transition temperature (Tc) up to 8.4
K and 8.3 K can be obtained by doping cobalt and sodium in alfa-FeSe with the
nominal composition of Fe0.92Co0.08Se and Na0.1FeSe, respectively. The
electrical resistivity and AC magnetic susceptibility of the prepared samples,
measured with physical property measurement system (PPMS), unambiguously
consistent with each other to indicate that the samples are superconductive.
The respective doping mechanisms for cobalt and sodium into the parent
alfa-FeSe are the Fe-site substitution and the interlayer insertion. It is the
first time that alfa-FeSe can be induced to be a superconductor with Na+
intercalated into the interlayers.

5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th