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Electron-Phonon Coupling and Surface Debye Temperature of Bi$_2$Te$_3$(111) from Helium Atom Scattering

Research paper by Anton Tamtögl, Patrick Kraus, Nadav Avidor, Martin Bremholm, Ellen M. J. Hedegaard, Bo B. Iversen, Marco Bianchi, Philip Hofmann, John Ellis, William Allison, Giorgio Benedek, Wolfgang E. Ernst

Indexed on: 24 Apr '17Published on: 24 Apr '17Published in: arXiv - Physics - Materials Science



Abstract

We have studied the topological insulator Bi$_2$Te$_3$(111) by means of helium atom scattering. The average electron-phonon coupling $\lambda$ of Bi$_2$Te$_3$(111) is determined by adapting a recently developed quantum-theoretical derivation of the helium scattering probabilities to the case of degenerate semiconductors. Based on the Debye-Waller attenuation of the elastic diffraction peaks of Bi$_2$Te$_3$(111), measured at surface temperatures between $110~\mbox{K}$ and $355~\mbox{K}$, we find $\lambda$ to be in the range of $0.04-0.11$. This method allows to extract a correctly averaged $\lambda$ and to address the discrepancy between previous studies. The relatively modest value of $\lambda$ is not surprising even though some individual phonons may provide a larger electron-phonon interaction. Furthermore, the surface Debye temperature of Bi$_2$Te$_3$(111) is determined as ${\rm \Theta}_D = (81\pm6)~\mbox{K}$. The electronic surface corrugation was analysed based on close-coupling calculations. By using a corrugated Morse potential a peak-to-peak corrugation of 9% of the lattice constant is obtained.