Terahertz Faraday and Kerr rotation spectroscopy of Bi1xSbx films in high magnetic fields up to 30 tesla

Xinwei Li, Katsumasa Yoshioka, Ming Xie, G. Timothy Noe, II, Woojoo Lee, Nicolas Marquez Peraca, Weilu Gao, Toshio Hagiwara, Ørjan S. Handegård, Li-Wei Nien, Tadaaki Nagao, Masahiro Kitajima, Hiroyuki Nojiri, Chih-Kang Shih, Allan H. MacDonald, Ikufumi Katayama, Jun Takeda, Gregory A. Fiete, and Junichiro Kono
Phys. Rev. B 100, 115145 – Published 19 September 2019

Abstract

We report results of terahertz Faraday and Kerr rotation spectroscopy measurements on thin films of Bi1xSbx, an alloy system that exhibits a semimetal-to-topological-insulator transition as the Sb composition x increases. By using a single-shot time-domain terahertz spectroscopy setup combined with a table-top pulsed minicoil magnet, we conducted measurements in magnetic fields up to 30 T, observing distinctly different behaviors between semimetallic (x<0.07) and topological insulator (x>0.07) samples. Faraday and Kerr rotation spectra for the semimetallic films showed a pronounced dip that blueshifted with the magnetic field, whereas spectra for the topological insulator films were positive and featureless, increasing in amplitude with increasing magnetic field and eventually saturating at high fields (>20 T). Ellipticity spectra for the semimetallic films showed resonances, whereas the topological insulator films showed no detectable ellipticity. To explain these observations, we developed a theoretical model based on realistic band parameters and the Kubo formula for calculating the optical conductivity of Landau-quantized charge carriers. Our calculations quantitatively reproduced all experimental features, establishing that the Faraday and Kerr signals in the semimetallic films predominantly arise from bulk hole cyclotron resonances while the signals in the topological insulator films represent combined effects of surface carriers originating from multiple electron and hole pockets. These results demonstrate that the use of high magnetic fields in terahertz magnetopolarimetry, combined with detailed electronic structure and conductivity calculations, allows us to unambiguously identify and quantitatively determine unique contributions from different species of carriers of topological and nontopological nature in Bi1xSbx.

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  • Received 2 July 2019

DOI:https://doi.org/10.1103/PhysRevB.100.115145

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Xinwei Li1,*, Katsumasa Yoshioka2,*, Ming Xie3,*, G. Timothy Noe, II1, Woojoo Lee3, Nicolas Marquez Peraca4, Weilu Gao1, Toshio Hagiwara2, Ørjan S. Handegård5, Li-Wei Nien5, Tadaaki Nagao5, Masahiro Kitajima2,5, Hiroyuki Nojiri6, Chih-Kang Shih3, Allan H. MacDonald3, Ikufumi Katayama2, Jun Takeda2, Gregory A. Fiete3,7,8, and Junichiro Kono1,4,9

  • 1Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA
  • 2Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan
  • 3Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
  • 4Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
  • 5National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
  • 6Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
  • 7Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
  • 8Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 9Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, USA

  • *These authors contributed equally.

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Issue

Vol. 100, Iss. 11 — 15 September 2019

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