Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 59: Superconductivity: Fe-based Superconductors - FeSe and others
TT 59.1: Vortrag
Donnerstag, 23. März 2017, 09:30–09:45, HSZ 103
Phonon spectrum of single-crystalline FeSe — •Tobias Engelhardt1, Khalil Zakeri Lori1, Thomas Wolf2, and Matthieu Le Tacon2 — 1Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, D-76131 Karlsruhe, Germany — 2Institut für Festkörperphysik, Karlsruhe Institute of Technology, Hermann-v.-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
Iron selenide is structurally the simplest iron-based superconductor and has been investigated extensively during the past years. Several experimental tools have been used to investigate the collective excitations, e.g. phonons, in this material. However, due to the lack of large single crystals, most of those experiments are performed on polycrystalline or powder samples. We report on the first phonon spectrum probed on the FeSe(001) surface by means of high-resolution electron energy-loss spectroscopy. Single crystals of FeSe are cleaved under ultra-high vacuum conditions and are subsequently measured above and below the nematic transition temperature. We observe five phonon modes and a phonon cutoff energy of about 42 meV at the center of Brillouin zone. These phonon modes disperse rather weakly while changing the momentum from zero up to the zone boundary, indicating that they are mainly of optical nature. We identify the origin of each phonon mode by comparing the experimental results to the ones of ab initio density functional calculations. Finally we comment on the role of temperature on the phonon spectrum.