Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropic ultrafast optical response of terahertz pumped graphene   We have measured the ultrafast anisotropic optical response of highly doped
graphene to an intense single cycle terahertz pulse. The time profile of the
terahertz-induced anisotropy signal at 800 nm has minima and maxima repeating
those of the pump terahertz electric field modulus. It grows with increasing
carrier density and demonstrates a specific nonlinear dependence on the
electric field strength. To describe the signal, we have developed a
theoretical model that is based on the energy and momentum balance equations
and takes into account optical phonons of graphene and substrate. According to
the theory, the anisotropic response is caused by the displacement of the
electronic momentum distribution from zero momentum induced by the pump
electric field in combination with polarization dependence of the matrix
elements of interband optical transitions.

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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org