Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Flat band in topological matter: possible route to room-temperature
  superconductivity   Topological media are systems whose properties are protected by topology and
thus are robust to deformations of the system. In topological insulators and
superconductors the bulk-surface and bulk-vortex correspondence gives rise to
the gapless Weyl, Dirac or Majorana fermions on the surface of the system and
inside vortex cores. In gapless topological media, the bulk-surface and
bulk-vortex correspondence produce topologically protected gapless fermions
without dispersion - the flat band. Fermion zero modes forming the flat band
are localized on the surface of topological media with protected nodal lines
and in the vortex core in systems with topologically protected Fermi points
(Weyl points). Flat band has an extremely singular density of states, and this
property may give rise in particular to surface superconductivity which in
principle could exist even at room temperature.

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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph