Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 21: Superconductivity: Poster Session

TT 21.24: Poster

Montag, 16. März 2015, 15:00–18:00, Poster B

Superconductivity from Magnetic Fluctuations in FeTe_1−xSe_x-Feedback of Double Stripe Magnetism on Itinerant Spin Excitations — •Masoud Mardani¹, Johannes knolle², Ilya Eremin³, and Roderich Moessner¹ — ¹Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany — ²TCM Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom — ³Institute for Theoretical Physics III, Ruhr-Universität Bochum, D-44801 Bochum, Germany

Iron-chalcogenide superconductors exhibit an unusual double stripe antiferromagnetic parent phase with ordering vector Q_AF = (π/2,π/2) (in the one iron unit cell). In addition, magnetic excitations in optimally doped systems are peaked at momenta Q_SF = (π,0)/(0,π), which is in contrast to most other families of iron-based superconductors. There, both the magnetic order of the parent compounds and the magnetic fluctuations in the superconducting state have the same momentum Q_SF, which is taken as a strong argument in favor of spin-fluctuation induced superconductivity. Here, we model iron-chalcogenides as a system of itinerant electrons coupled to localized electrons responsible for the double stripe magnetism. We study the feedback of this unusual magnetic order on the itinerant spin excitations at Q_SF and show that they increase with decreasing magnetism. We make connection to recent INS experiments and reproduce qualitatively the behavior of magnetic excitations in FeTe_1−xSe_x from x=0 towards x=0.4.