Measuring Valley Polarization in Two-Dimensional Materials with Second-Harmonic Spectroscopy

  title={Measuring Valley Polarization in Two-Dimensional Materials with Second-Harmonic Spectroscopy},
  author={Yi Wei Ho and Henrique G. Rosa and Ivan A. Verzhbitskiy and Manuel J. L. F. Rodrigues and Takashi Taniguchi and Kenji Watanabe and Goki Eda and Vitor M. Pereira and Jos{\'e} Viana‐Gomes},
  journal={ACS Photonics},
Inducing a population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such valley imbalance (a valley polarization) that directly exploits this symmetry reduction as well as the unique fingerprints it has in the polarization-dependent second-harmonic generation. We describe the principle and detection scheme in the context of hexagonal two-dimensional crystals, which include graphene-based systems and the… 
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