Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The effects of Coulomb interactions on the superconducting gaps in
  iron-based superconductors   Recent angle-resolved photoemission spectroscopy measurements of Co-doped
LiFeAs report a large and robust superconducting gap on the $\Gamma$-centered
hole band that lies 8 meV below the Fermi level. We show that, unlike a
conventional superconductor described by BCS theory, a multiband system with
strong interband Coulomb interactions can explain these observations. We model
LiFeAs with a five-band model in which the shallow hole band is coupled with
the other bands by only Coulomb interactions. Using Eliashberg theory, we find
reasonable interaction parameters that reproduce the $T_c$ and all five gaps of
LiFeAs. The energy independence of the Coulomb interactions then ensures the
robustness of the gap induced on the shallow band. Furthermore, due to the
repulsive nature of the Coulomb interactions, the gap changes sign between the
shallow band and the other hole pockets, corresponding to an unconventional
$s_{\pm}$ gap symmetry. Unlike other families of iron-based superconductors,
the gap symmetry of LiFeAs has not been ascertained experimentally. The
experimental implications of this sign-changing state are discussed.

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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
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The categories of this paper are: stat
2
The categories of this paper are: math
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph