Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rotons in Optical Excitation Spectra of Monolayer Semiconductors   Optically generated excitons dictate the absorption and emission spectrum of
doped semiconductor transition metal dichalcogenide monolayers. We show that
upon increasing the electron density, the elementary optical excitations
develop a roton-like dispersion, evidenced by a shift of the lowest energy
state to a finite momentum on the order of the Fermi momentum. This effect
emerges due to Pauli exclusion between excitons and the electron Fermi sea, but
the robustness of the roton minimum in these systems is a direct consequence of
the long-range nature of the Coulomb interaction and the nonlocal dielectric
screening characteristic of monolayers. Finally, we show that the emergence of
rotons could be related to hitherto unexplained aspects of photoluminescence
spectra in doped transition metal dichalcogenide monolayers.

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The categories of this paper are: patt-sol
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph