Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interacting Dirac Fermions on a Topological Insulator in a Magnetic
  Field   We have studied the fractional quantum Hall states on the surface of a
topological insulator thin film in an external magnetic field, where the Dirac
fermion nature of the charge carriers have been experimentally established only
recently. Our studies indicate that the fractional quantum Hall states should
indeed be observable in the surface Landau levels of a topological insulator.
The strength of the effect will however be different, compared to that in
graphene, due to the finite thickness of the topological insulator film and due
to the admixture of Landau levels of the two surfaces of the film. At a small
film thickness, that mixture results in a strongly non-monotonic dependence of
the excitation gap on the film thickness. At a large enough thickness of the
film, the excitation gap in the lowest two Landau levels are comparable in
strength.

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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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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: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: eess