Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 15: Superconductivity: Fe-based Superconductors - Other Materials and Theory

TT 15.5: Vortrag

Montag, 1. April 2019, 16:00–16:15, H23

Strain-derivative of thermoelectric coefficients: a sensitive probe for nematic fluctuations — •Federico Caglieris1, Christoph Wuttke1, Xiaochen Hong1, Steffen Sykora1, Rhea Kappenberger1, Saicharan Aswartham1, Sabine Wurmehl1, Bernd Büchner1,2,3, and Christian Hess1,21Leibniz Institute for Solid State and Materials Research, 01069 Dresden, Germany — 2Institut für Festkörperphysik, TU Dresden, 01069 Dresden — 3Center for Transport and Devices, TU Dresden, 01069 Dresden, Germany

The role of nematic fluctuations in iron-based superconductors is still a strongly debated topic with many open questions concerning their origin and their relationship with the emerging superconductivity. In this work we tackle this issue with a new experimental technique, which combines the high sensitivity of the thermoelectric transport properties with the gentle strain offered by a piezoelectric device. The idea is to use the strain derivative of the Seebeck and the Nernst coefficients as a new tool to investigate the nematicity in the 1111 family of iron based superconductors, so far almost unexplored due to the lack of sizable single crystals. The main outcomes of our study are: i) nematic fluctuations are peaked at the structural transition temperature TS and not at the magnetic one; ii) not all the bands contribute to the measured anisotropy; iii) the Curie-Weiss scaling, previously found for the resistivity anisotropy for T>TS, also exists in the Seebeck and Nernst anisotropy, suggesting the existence of a common mechanism. Our results point towards an orbital origin of nematicity.

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