Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state

Ken N. Okada, Youtarou Takahashi, Masataka Mogi, Ryutaro Yoshimi, Atsushi Tsukazaki, Kei S. Takahashi, Naoki Ogawa, Masashi Kawasaki, Yoshinori Tokura

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57 Citations (Scopus)

Abstract

Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit.

Original languageEnglish
Article number12245
JournalNature communications
Volume7
DOIs
Publication statusPublished - 2016 Jul 20

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)

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    Okada, K. N., Takahashi, Y., Mogi, M., Yoshimi, R., Tsukazaki, A., Takahashi, K. S., Ogawa, N., Kawasaki, M., & Tokura, Y. (2016). Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state. Nature communications, 7, [12245]. https://doi.org/10.1038/ncomms12245