Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

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

TT 15.3: Vortrag

Montag, 1. April 2019, 15:30–15:45, H23

Disentangling magnetism and superconductivity in LaOFeAs: A NQR study — •Piotr Lepucki1, Igor Morozov1,2, Ilya Silkin2, Rhea Kappenberger1, Sabine Wurmehl1, Saicharan Aswartham1, Markus Witschel1, Bernd Büchner1, and Hans-Joachim Grafe11IFW Dresden, Helmholtzstraße 20, 01069 Dresden — 2Moscow State University, Moscow, Russia

The nature of the coexistence of magnetism and superconductivity in iron-based superconductors is still not well understood. The main discussion is whether there is a microscopic phase coexistence or phase separation (e.g. [1, 2]). We performed 75As nuclear quadrupole resonance (NQR) measurements on P- and Co-doped LaOFeAs powders in search of different behavior in magnetic and superconducting samples, and compare our results to F doped samples [3]. Our measurements show that independent of the dopant (isovalent P doping, in plane Co doping, or out of plane F doping), the electronic structure is changed only locally, leading to regions with different charge environments of the As, and therefore well separated NQR peaks. The relative weight of these regions is equal to the relative spectral weight of the corresponding NQR peaks and is a measure of the doping level [3]. Below the magnetic or superconducting transitions, these NQR peaks change differently, indicating that those regions which are largely unaffected by the doping are driving the magnetism, whereas the doped regions harbor superconductivity. These results suggest a microscopic phase separation in LaOFeAs irrespective of the dopant type.
PRB 97, 224508
PRB 80, 024508
PRB 94, 014514

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