Nanoscale Surface Dynamics of Bi${}_2$Te${}_3$(111): Observation of a Prominent Surface Acoustic Wave and the Role of van der Waals Interactions

Abstract

We present a combined experimental and theoretical study of the surface vibrational modes of the topological insulator Bi${}_2$Te${}_3$. Using high-resolution helium-3 spin-echo spectroscopy we are able to resolve the acoustic phonon modes of Bi${}_2$Te${}_3$(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.

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• The electron-phonon coupling strength at metal surfaces directly determined from the Helium atom scattering Debye-Waller factor
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Cited by in corpus (7)

• Phononic Helical Nodal Lines with $\mathcal{P}\mathcal{T}$ Protection in MoB${}_2$
• Origin of the Electron-Phonon Interaction of Topological Semimetal Surfaces Measured with Helium Atom Scattering
• Vibrational Spectra of Pb2Bi2Te3, PbBi2Te4 and PbBi4Te7 Topological Insulators: Temperature Dependent Raman and Theoretical Insight from DFT Simulations
• THz Surface Modes and Electron-Phonon Coupling in Bi${}_2$Se${}_3$(111)
• Transfer matrix theory of surface spin echo experiments with molecules
• Inter-adsorbate forces and coherent scattering in helium spin-echo experiments
• Observation of Dirac Charge Density Waves in Bi${}_2$Te${}_2$Se