Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Raman scattering from Higgs mode oscillations in the two-dimensional
  antiferromagnet Ca$_2$RuO$_4$   We present and analyze Raman spectra of the Mott insulator Ca$_2$RuO$_4$,
whose quasi-two-dimensional antiferromagnetic order has been described as a
condensate of low-lying spin-orbit excitons with angular momentum $J_{eff}=1$.
In the $A_g$ polarization geometry, the amplitude (Higgs) mode of the
spin-orbit condensate is directly probed in the scalar channel, thus avoiding
infrared-singular magnon contributions. In the $B_{1g}$ geometry, we observe a
single-magnon peak as well as two-magnon and two-Higgs excitations. Model
calculations using exact diagonalization quantitatively agree with the
observations. Together with recent neutron scattering data, our study provides
strong evidence for excitonic magnetism in Ca$_2$RuO$_4$ and points out new
perspectives for research on the Higgs mode in two dimensions.

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The categories of this paper are: supr-con
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph