Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 110: Superconductivity: Fe-based Superconductors - 1111 and Others
TT 110.4: Vortrag
Freitag, 16. März 2018, 10:15–10:30, H 3010
The nematic phase in LaFe1−xCoxAsO probed by thermal expansion — •Francesco Scaravaggi1,2, Sven Sauerland3, Rhea Kappenberger1,2, Liran Wang1,3, Saicharan Aswartham1, Sabine Wurmehl1,2, Rüdiger Klingeler3, Anja U. B. Wolter1, and Bernd Büchner1,2 — 1Leibniz-Institute for Solid State and Materials Research, IFW Dresden, Dresden, Germany — 2Institute for Solid State Physics, TU Dresden, Dresden, Germany — 3Kirchhoff Institute for Physics, Heidelberg University, Heidelberg, Germany
Nematicity in electron doped 1111 systems LaFe1−xCoxAsO (x > 0) has been studied on polycrystalline samples, revealing a rich phase diagram. Measurements suggest an abrupt suppression of the AFM/orthorhombic phase with doping upon approaching the superconducting dome, but signatures of the nematic phase could still be detected in the underdoped region. In order to better understand the unique La-1111 phase diagram among the Fe-based superconductors, we report a systematic investigation of the evolution of the nematic state of Co-doped LaFeAsO single crystals. The availability of macroscopic phase pure single crystals for different doping compositions allows us to directly probe structural changes via high resolution dilatometry. Detwinning of the crystals, achieved by the application of a small uniaxial force in the dilatometer, permits us to probe thermal expansion in different crystallographic directions (a,b,c). From this we can obtain information about the structural order parameter (δ) as a function of temperature and doping, thus allowing us to study the nematic phase at different regions in the phase diagram.