Nanoscale Surface Dynamics of Bi2Te3(111): Observation of a Prominent Surface Acoustic Wave and the Role of van der Waals Interactions

Anton Tamtögl, Davide Campi, Martin Bremholm, Ellen M. J. Hedegaard, Bo Brummerstedt Iversen, Marco Bianchi, Philip Hofmann, Nicola Marzari, Giorgio Benedek, John Ellis, William Allison

Research output: Contribution to journalArticle

Abstract

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 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
Pages (from-to)14627-14636
JournalNanoscale
Volume10
Early online date16 Jul 2018
DOIs
Publication statusPublished - 16 Jul 2018

Keywords

  • Topological insulator
  • surface phonons
  • density functional theory
  • Atom scattering
  • Surface analysis

Fields of Expertise

  • Advanced Materials Science

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