Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 79: Superconductivity: Fe-based Superconductors - 122

TT 79.3: Vortrag

Donnerstag, 10. März 2016, 16:00–16:15, H21

Electronic correlations in the hole-doped superconductor RbFe₂As₂ probed via ⁷⁵As NMR — •S. Molatta^1,2,3, Z. Zhang¹, D. Dmytriieva¹, S. Khim⁴, S. Wurmehl^2,3,4, H.-J. Grafe⁴, B. Büchner^2,3,4, H. Kühne¹, and J. Wosnitza^1,2,3 — ¹Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Germany — ²TU Dresden, Germany — ³DFG GRK-1621 — ⁴IFW Dresden, Germany

We will present latest ⁷⁵As NMR data in the normal state of the stoichiometric superconductor RbFe₂As₂. This will be put into context to known results for the heavily hole-doped compound KFe₂As₂. The static and dynamic magnetic correlations were probed via measurements of the Knight shift and nuclear spin-lattice relaxation rate in a wide temperature range from 0.3 to 300 K. Although neither a magnetic nor a structural transition were observed down to lowest temperatures, the very close proximity of the ground state to a magnetic instability is indicated by a pronounced Curie-Weiss-like behavior of spin fluctuations. At around 100 K, we find a maximum of the Knight shift and a changing exponent of the temperature-dependent relaxation rate. This is phenomenologically similar to the case of KFe₂As₂ and was proposed to stem from a incoherence-coherence crossover mechanism of electronic correlations.