Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perturbation Theory of High-Tc Superconductivity in Iron Pnictides   The high-transition-temperature (high-Tc) superconductivity discovered
recently in iron pnictides is analyzed within a perturbation theory.
Specifically, the probable pairing symmetry, the doping dependence of the
transition temperature and the pairing mechanism are studied by solving the
Eliashberg equation for multi-band (2- and 5-band) Hubbard models with
realistic electronic structures. The effective pairing interaction is expanded
perturbatively in the on-site Coulomb integrals up to third order. Our
perturbative weak-coupling approach shows that sufficiently large eigenvalues
of the Eliashberg equation are obtained to explain the actual high transition
temperatures by taking realistic on-site Coulomb integrals in the 5-band model.
Thus, unconventional (non-phonon-mediated) superconductivity is highly likely
to be realized. The superconducting order parameter does not change its sign on
the Fermi surfaces, but it does change between the electron and hole Fermi
surfaces. Consequently, the probable pairing symmetry is always "a nodeless
extended s-wave symmetry (more specifically, an s_{+-}-wave symmetry)" over the
whole parameter region that we investigated. It is suggested that the 2-band
model is insufficient to explain the high values of Tc.

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The categories of this paper are: funct-an
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: mtrl-th