Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiband Electronic Raman Scattering in Bilayer Superconductors   A theory of electronic Raman scattering in the presence of several energy
bands crossing the Fermi surface is developed. The contributions to the light
scattering cross section are calculated for each band and it is shown that the
cross section can be written in terms of the sum of the single band
contributions and a mixing term which only contributes to the fully symmetric
channels $(A_{1g})$. Particular emphasis is placed on screening in bilayer
superconductors. Since any charge fluctuation with long range character in real
space is screened by the Coulomb interaction, the relevant fluctuations in a
single layer case are induced between different parts of the Fermi surface. In
a single band $d$-wave superconductor the scattering at energy transfer twice
the maximum gap $\Delta_{max}$ is dominated by those parts of the Fermi surface
where $\Delta^2({\bf k})$ is largest. As a consequence, the fully symmetric
($A_{1g}$) scattering is screened. In the case of a bilayer superconductor
however, the charge transfer is possible between layers inside the unit cell.
Therefore a formalism is considered which is valid for general band structure,
superconducting energy gaps, and inter-layer hopping matrix elements. The
spectra is calculated for La 2:1:4 and Y 1:2:3 as representative single and
bilayer superconductors. The mixing term is found to be negligible and thus the
response is well approximated by the sum of the contributions from the
individual bands. The theory imposes strong constraints on both the magnitude
and symmetry of the energy gap for the bilayer cuprates, and indicates that a
nearly identical energy gap of $d_{x^{2}-y^{2}}$ symmetry provides a best fit
to the data. However, the $A_{1g}$ part of the spectrum depends sensitively on
many parameters.

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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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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: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph