Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Surface State Spectroscopy I
O 8.9: Talk
Monday, March 7, 2016, 12:45–13:00, H4
Evidence for an extremely low-lying electron-hole excitation mode in the Sb(111)-phonon dispersion measured by HAS — •Patrick Kraus1, Florian Apolloner1, Christian Gösweiner1, Giorgio Benedek2,3, and Wolfgang E. Ernst1 — 1Institute of Experimental Physics, Graz Univerity of Technology, Graz, Austria — 2Donostia International Physics Center (DIPC), San Sebastian/Donostia, Spain — 3Dipartimiento di Scienza dei Materiali, Universita di Milano-Bicocca, Milano, Italy
The semimetal antimony (Sb) is an attractive candidate for studying the properties of topological surfaces. Quite recently the surface phonon dispersion curve of Sb(111) as well as the influences of electron-phonon interactions were calculated using DFPT. However, there has been a shortage of experimental data for comparison and verification of the models used. Hence, measurements on antimony are long overdue. As a surface sensitive technique, Helium Atom Scattering (HAS) allows investigating elastic as well as inelastic phenomena associated with structure and dynamics of the electronic corrugation slightly above the Sb(111) surface. Besides confirming the expected surface phonon dispersion curves, recent inelastic HAS measurements on Sb(111) revealed multiple unexpected branches. One of them, lying completely below the Rayleigh curve of the phonon dispersion with a maximum energy at the K-point below 3*meV, can not be assigned to any known feature up to now. The electronic peculiarities in the case of Sb(111) can lead to the formation of defined electon-hole excitation branches which may be detected via iHAS measurements.