Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Uniaxial Strain in Graphene by Raman Spectroscopy: G peak splitting,
  Gruneisen Parameters and Sample Orientation   Graphene is the two-dimensional building block for carbon allotropes of every
other dimensionality. Since its experimental discovery, graphene continues to
attract enormous interest, in particular as a new kind of matter, in which
electron transport is governed by a Dirac-like wave equation, and as a model
system for studying electronic and phonon properties of other, more complex,
graphitic materials[1-4]. Here, we uncover the constitutive relation of
graphene and probe new physics of its optical phonons, by studying its Raman
spectrum as a function of uniaxial strain. We find that the doubly degenerate
E2g optical mode splits in two components, one polarized along the strain and
the other perpendicular to it. This leads to the splitting of the G peak into
two bands, which we call G+ and G-, by analogy with the effect of curvature on
the nanotube G peak[5-7]. Both peaks red shift with increasing strain, and
their splitting increases, in excellent agreement with first-principles
calculations. Their relative intensities are found to depend on light
polarization, which provides a useful tool to probe the graphene
crystallographic orientation with respect to the strain. The singly degenerate
2D and 2D' bands also red shift, but do not split for small strains. We study
the Gruneisen parameters for the phonons responsible for the G, D and D' peaks.
These can be used to measure the amount of uniaxial or biaxial strain,
providing a fundamental tool for nanoelectronics, where strain monitoring is of
paramount importance[8, 9]

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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: math
30
The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th