Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Valley separation in graphene by polarized light   We show that the optical excitation of graphene with polarized light leads to
the pure valley current where carriers in the valleys counterflow. The current
in each valley originates from asymmetry of optical transitions and electron
scattering by impurities owing to the warping of electron energy spectrum. The
valley current has strong polarization dependence, its direction is opposite
for normally incident beams of orthogonal linear polarizations. In undoped
graphene on a substrate with high susceptibility, electron-electron scattering
leads to an additional contribution to the valley current that can dominate.

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The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin