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 Büchner^1,3, and Christian Hess¹ — ¹Leibniz-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.