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TT: Fachverband Tiefe Temperaturen
TT 52: Superconductivity: Fe-based Superconductors - FeSe and LiFeAs
TT 52.7: Talk
Wednesday, March 14, 2018, 11:00–11:15, HFT-FT 101
evidence of orbital selective cooper pairing within surface unit cell of FeSe — •Fang Yang1, Jasmin Jandke1, Peter Adelmann2, Markus Klug3, Thomas Wolf2, Jörg Schmalian3, and Wulf Wulfhekel1 — 1Physikalisches institut, KIT, Karlsruhe, Germany — 2Institut für Festkörperphysik, KIT, Karlsruhe, Germany — 3Institut für Theorie der Kondensierten Materie, KIT, Karlsruhe, Germany
Numerous attempts have been made to demonstrate the multi-band nature of superconductivity in bulk FeSe in the nematic phase. To investigate this multi-band character, we determined the electronic density of states at the surface of FeSe with high energy and spatial resolution using a 40 mK dilution STM. A high spatial resolution was achieved using an STM tip with electronic p-states, which not only gives a higher lateral resolution compared to an s-state tip but also is sensitive to the surface symmetry. With this, we were able to resolve the superconducting gap of all five bands cutting the Fermi energy and, in combination with the high lateral resolution, the spatial distribution of the intensity of the quasiparticle peaks within the unit cell. By comparison with the expected d-orbital wave functions, we propose that different gaps are of particular orbital nature.