Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fractional Quantum Hall Effect at $\nu=1/2$ in Hole Systems Confined to
  GaAs Quantum Wells   We observe fractional quantum Hall effect (FQHE) at the even-denominator
Landau level filling factor $\nu=1/2$ in two-dimensional hole systems confined
to GaAs quantum wells of width 30 to 50 nm and having bilayer-like charge
distributions. The $\nu=1/2$ FQHE is stable when the charge distribution is
symmetric and only in a range of intermediate densities, qualitatively similar
to what is seen in two-dimensional electron systems confined to approximately
twice wider GaAs quantum wells. Despite the complexity of the hole Landau level
structure, originating from the coexistence and mixing of the heavy- and
light-hole states, we find the hole $\nu=1/2$ FQHE to be consistent with a
two-component, Halperin-Laughlin ($\Psi_{331}$) state.

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The categories of this paper are: stat
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The categories of this paper are: quant-ph
3
The categories of this paper are: physics
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin