Nanoscale surface dynamics of Bi2Te3(111): observation of a prominent surface acoustic wave and the role of van der Waals interactions

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  • Anton Tamtoegl, Graz Univ Technol, Graz University of Technology, Inst Expt Phys
  • ,
  • Davide Campi, Ecole Polytech Fed Lausanne, Ecole Polytechnique Federale de Lausanne, Natl Ctr Computat Design & Discovery Novel Mat MA
  • ,
  • Martin Bremholm
  • Ellen M. J. Hedegaard
  • ,
  • Bo B. Iversen
  • Marco Bianchi
  • Philip Hofmann
  • Nicola Marzari, Ecole Polytech Fed Lausanne, Ecole Polytechnique Federale de Lausanne, Natl Ctr Computat Design & Discovery Novel Mat MA
  • ,
  • Giorgio Benedek, Univ Basque Country, University of Basque Country, DIPC, EHU UPV
  • ,
  • John Ellis, Cavendish Lab, University of Cambridge
  • ,
  • William Allison, Cavendish Lab, University of Cambridge

We present a combined experimental and theoretical study of the surface vibrational modes of the topological insulator Bi2Te3. Using high-resolution helium-3 spin-echo spectroscopy we are able to resolve the acoustic phonon modes of Bi2Te3(111). The low energy region of the lattice vibrations is mainly dominated by the Rayleigh mode which has been claimed to be absent in previous experimental studies. The appearance of the Rayleigh mode is consistent with previous bulk lattice dynamics studies as well as theoretical predictions of the surface phonon modes. Density functional perturbation theory calculations including van der Waals corrections are in excellent agreement with the experimental data. Comparison of the experimental results with theoretically obtained values for films with a thickness of several layers further demonstrate, that for an accurate theoretical description of three-dimensional topological insulators with their layered structure the inclusion of van der Waals corrections is essential. The presence of a prominent surface acoustic wave and the contribution of van der Waals bonding to the lattice dynamics may hold important implications for the thermoelectric properties of thin-film and nanoscale devices.

Original languageEnglish
JournalNanoscale
Volume10
Issue30
Pages (from-to)14627-14636
Number of pages10
ISSN2040-3364
DOIs
Publication statusPublished - 14 Aug 2018

    Research areas

  • HELIUM ATOM SCATTERING, TOPOLOGICAL INSULATOR, LATTICE-VIBRATIONS, RAMAN, PHONONS, DENSITY, FILMS

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