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Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 49: Poster Session: Superconductivity

TT 49.15: Poster

Wednesday, April 3, 2019, 15:00–18:30, Poster D

Elastotransport and Nernst effect in 122- and 1111-Fe-based superconductors: Evidence for superconductivity driven by nematic fluctuations — •Christoph Wuttke1, Federico Caglieris1, Xiaochen Hong1, Steffen Sykora1, Frank Steckel1, Seunghyun Kim1, Rhea Kappenberger1, Saicharan Aswartham1, Sabine Wurmehl1, Sheng Ran2, Paul C. Canfield2, Bernd Büchner1,3, and Christian Hess11Leibniz-Institute for Solid State and Materials Research, IFW-Dresden, 01069 Dresden, Germany — 2Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA — 3Institut für Festkörperphysik, TU Dresden, 01069 Dresden, Germany

The role of nematic fluctuations in the appearance of high temperature superconductivity is still controversial. In this work we investigate the phase diagrams of BaFe2As2 and LaFeAsO as a function of electron-doping through elastotransport and Nernst effect measurements. We obtain an anomalously large Nernst coefficient in the tetragonal phase, upon doping its magnitude strikingly mimicking the superconducting dome. Similar but slightly different non-monotonic behavior is found for the elastoresistivity. Using a minimal orbital model for iron-based superconductors we show that the Nernst coefficient couples directly to the nematic fluctuations. We explain the difference between elastoresistivity and Nernst effect by incorporating the coupling to a soft phonon mode in our theory. Thus, our experimental results provide supportive evidence that nematic fluctuations are crucial for the formation of the superconducting state in iron-based superconductors.

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