Berlin 2018 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 52: Superconductivity: Fe-based Superconductors - FeSe and LiFeAs
TT 52.9: Talk
Wednesday, March 14, 2018, 11:45–12:00, HFT-FT 101
Unconventional pairing versus phonon mediated superconductivity in single FeSe layers — •Jasmin Jandke1, Fang Yang1, Patrik Hlobil2, Tobias Engelhardt1, Chunlei Gao3, Jörg Schmalian2,4, and Wulf Wulfhekel1 — 1Physikalisches Institut, KIT, 76131 Karlsruhe, Germany — 2Institut für Theorie der Kondensierten Materie, KIT, 76131 Karlsruhe, Germany — 3State Key Laboratory of Surface Physics and Department of Physics, Fudan University Shanghai 200433, China — 4Institut für Festörperphysik, KIT, 76344 Karlsruhe, Germany
Both conventional [1] and unconventional [2] mechanisms
have been discussed for a single layer FeSe films on SrTiO3 showing a Tc of 60-100 K [3,4], i.e. an order of magnitude larger than in bulk FeSe.
Here we report a direct measurement of the electron-boson coupling in FeSe on SrTiO3
using inelastic tunneling spectroscopy. We exclude strong electron-phonon coupling except for
places near structural domain boundaries in the FeSe layer. Instead, the bosonic excitation spectrum is shown to be
fully gapped below Tc in agreement with an electronic pairing mechanism. By deconvolution of the experimental data, we were able to reconstruct the electron-boson coupling function, which shows beside a gap a characteristic peak at the expected resonance mode energy of paramagnons.
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