Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fe-based superconductors: seven years later   Iron-based superconductors were discovered seven years ago, in 2008. This
short review summarizes what we learned about these materials over the last
seven years, what are open questions, and what new physics we expect to extract
from studies of this new class of high-temperature superconductors.

7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg