Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Activation of new Raman modes by inversion symmetry breaking in type II
  Weyl semimetal candidate T'-MoTe2   We synthesized distorted octahedral(T') molybdenum ditelluride (MoTe2) and
investigated its vibrational properties with Raman spectroscopy, density
functional theory and symmetry analysis. Compared to the results from high
temperature centrosymmetric monoclinic (T'mo) phase, four new Raman bands
emerge in the low temperature orthorhombic (T'or) phase, which was recently
predicted to be a type II Weyl semimetal. Crystal-angle-dependent,
light-polarization-resolved measurements indicate that all the observed Raman
peaks belong to two categories: those vibrating along the zigzag Mo atomic
chain (z-mode) and those vibrating in the mirror plane (m-mode) perpendicular
to the zigzag chain. Interestingly the low energy shear z-mode and shear
m-mode, absent from the T'mo spectra, become activated when sample cooling
induces a phase transition to the T'or crystal structure. We interpret this
observation as a consequence of inversion-symmetry breaking, which is crucial
for the existence of Weyl fermions in the layered crystal. Our temperature
dependent Raman measurements further show that both the high energy m-mode at
130 cm-1 and the low energy shear m-mode at 12 cm-1 provide useful gauges for
monitoring the broken inversion symmetry in the crystal.

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The categories of this paper are: cs
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: econ
37
The categories of this paper are: supr-con