Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lattice vibrations of alpha'-NaV_2O_5 in the low-temperature phase.
  Magnetic bound states?   We report high resolution polarized infrared studies of the quarter-filled
spin ladder compound alpha'-NaV_2O_5 as a function of temperature (5K <= T <=
300K). Numerous new modes were detected below the temperature T_c=34K of the
phase transition into a charge ordered nonmagnetic state accompanied by a
lattice dimerization. We analyse the Brillouin zone (BZ) folding due to lattice
dimerization at T_c and show that some peculiarities of the low-temperature
vibrational spectrum come from quadruplets folded from the BZ point (1/2, 1/2,
1/4). We discuss an earlier interpretation of the 70, 107, and 133cm-1 modes as
magnetic bound states and propose the alternative interpretation as folded
phonon modes strongly interacting with charge and spin excitations.

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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph