Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Control of Exciton Valley Coherence in Transition Metal Dichalcogenide
  Monolayers   The direct gap interband transitions in transition metal dichalcogenides
monolayers are governed by chiral optical selection rules. Determined by laser
helicity, optical transitions in either the $K^+$ or $K^-$ valley in momentum
space are induced. Linearly polarized laser excitation prepares a coherent
superposition of valley states. Here we demonstrate the control of the exciton
valley coherence in monolayer WSe2 by tuning the applied magnetic field
perpendicular to the monolayer plane. We show rotation of this coherent
superposition of valley states by angles as large as 30 degrees in applied
fields up to 9 T. This exciton valley coherence control on ps time scale could
be an important step towards complete control of qubits based on the valley
degree of freedom.

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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
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The categories of this paper are: econ
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex