Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strong and Anisotropic Third Harmonic Generation in Monolayer and
  Multilayer ReS$_2$   We report observation of strong and anisotropic third harmonic generation
(THG) in monolayer and multilayer ReS$_2$. The third-order nonlinear optical
susceptibility of monolayer ReS$_2$, $\left| \chi^{(3)} \right|$ is on the
order of $10^{-18} $ m$^2$/V$^2$, which is about one order of magnitude higher
than reported results for hexagonal-lattice transition metal dichalcogenides
such as MoS$_2$. A similar magnitude for the third-order nonlinear optical
susceptibility was also obtained for a multilayer sample. The intensity of the
THG field was found to be dependent on the direction of the incident light
polarization for both monolayer and multilayer samples. A point group symmetry
analysis shows that such anisotropy is not expected from a perfect $1T$
lattice, and must arise from the distortions in the ReS$_2$ lattice. Our
results show that THG measurements can be used to characterize lattice
distortions of two-dimensional materials, and that lattice distortions are
important for the nonlinear optical properties of such materials.

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The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci