Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resonant Inelastic X-ray Scattering Study of Electron-Exciton Coupling
  in High-Tc Cuprates   Explaining the mechanism of superconductivity in the high-$T_c$ cuprates
requires an understanding of what causes electrons to form Cooper pairs.
Pairing can be mediated by phonons, the screened Coulomb force, spin or charge
fluctuations, excitons, or by a combination of these. An excitonic pairing
mechanism has been postulated, but experimental evidence for coupling between
conduction electrons and excitons in the cuprates is sporadic. Here we use
resonant inelastic x-ray scattering (RIXS) to monitor the temperature
dependence of the $\underline{d}d$ exciton spectrum of
Bi$_2$Sr$_2$CaCu$_2$O$_{8-x}$ (Bi-2212) crystals with different charge carrier
concentrations. We observe a significant change of the $\underline{d}d$ exciton
spectra when the materials pass from the normal state into the superconductor
state. Our observations show that the $\underline{d}d$ excitons are strongly
coupled to the Cooper pairs. This coupling may therefore play an important role
in stabilizing the superconducting state.

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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph