Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical two-photon nonlinear waves in two-dimensional materials   A theory of an optical two-photon breather in a graphene monolayer (or
graphene-like two-dimensional material) is constructed. The system of the
material equations for two-photon transitions and the wave equation for
transverse magnetic polarized modes of the surface plasmon polaritons are shown
to reduce to the nonlinear Schr\"odinger equation with damping. Explicit
analytical expressions for a surface small intensity two-photon breather
(0$\pi$ pulse) of self-induced transparency are obtained. It is shown that the
optical conductivity of graphene reduces the amplitude of the surface
two-photon nonlinear wave during the propagation. The one-photon and two-photon
breathers in graphene are compared and have obtained that the differences
between their parameters are significant.

2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys