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Temperature-dependent electron and phonon dynamics in the ternary topological insulator (Bi1−xSbx)2Te3 at terahertz frequencies

Alexander Stroh1, Hassan A. Hafez1,*, Pascal Strathkötter1, Andrew D. Burnett3, John Kendrick3, Alessandra Di Gaspare4, Maik Gärner1, Judith Bünte1, Chiara Seidel1 et al.

Ahmet Yagmur4, Craig S. Knox2,4, Matthew Vaughan2, Nathan Fox2, Satoshi Sasaki4, Andreas Hütten1, Edmund Linfield2, Miriam S. Vitiello5, Joshua Freeman2, and Dmitry Turchinovich1,†

  • *Contact author: hafez@physik.uni-bielefeld.de
  • †Contact author: dmtu@physik.uni-bielefeld.de
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Phys. Rev. B 112, 214303 – Published 1 December, 2025

DOI: https://doi.org/10.1103/y1qg-vjnz

Abstract

We investigate the temperature-dependent free electron conduction, terahertz phonon modes, and electron-phonon interactions, in the ternary topological insulator (Bi1−xSbx)2Te3. Terahertz time-domain spectroscopy and Raman spectroscopy on three n-type (Bi1−xSbx)2Te3 samples of various thicknesses were performed. Strong phonon activity and electron–phonon coupling were experimentally revealed and found to be sensitive to temperature changes and subtle structural variations between the samples. The experimental results, well described by Drude-Lorentz-Fano model, were compared to density functional theory calculations, yielding the phonon mode assignment. Further, an additional broadened background absorption was observed and attributed to the morphology of the conductive top surface of the samples.

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Phys. Rev. B 112, 214303– Published 1 December, 2025
  • Received 20 May 2025
  • Revised 24 September 2025
  • Accepted 20 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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