Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magneto-Optical Measurements of the Negatively Charged 2$s$ Exciton in
  WSe$_2$   Monolayer transition metal dichalcogenides host a variety of optically
excited quasiparticles species that stem from two-dimensional confinement
combined with relatively large carrier effective masses and reduced dielectric
screening. The magnetic response of these quasiparticles gives information on
their spin and valley configurations, nuanced carrier interactions, and insight
into the underlying band structure. Recently, there have been several reports
of 2$s$/3$s$ charged excitons in TMDs, but very little is still known about
their response to external magnetic fields. Using photoluminescence excitation
spectroscopy, we observe the presence of the 2$s$ charged exciton and report
for the first time its response to an applied magnetic field. We benchmark this
response against the neutral exciton and find that both the 2$s$ neutral and
charged excitons exhibit similar behavior with $g$-factors of
g$_{\rm{X_0^{2s}}}$=-5.20$\pm$0.11$\mu_{\rm{B}}$ and
g$_{\rm{X_-^{2s}}}$=-4.98$\pm$0.11$\mu_{\rm{B}}$, respectively.

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The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
2
The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg