Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photoluminescence investigations of 2D hole Landau levels in p-type
  single Al_{x}Ga_{1-x}As/GaAs heterostructures   We study the energy structure of two-dimensional holes in p-type single
Al_{1-x}Ga_{x}As/GaAs heterojunctions under a perpendicular magnetic field.
Photoluminescence measurments with low densities of excitation power reveal
rich spectra containing both free and bound-carrier transitions. The
experimental results are compared with energies of valence-subband Landau
levels calculated using a new numerical procedure and a good agreement is
achieved. Additional lines observed in the energy range of free-carrier
recombinations are attributed to excitonic transitions. We also consider the
role of many-body effects in photoluminescence spectra.

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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
5
The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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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: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th