Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Superconductivity: Fe-based Superconductors - 122

TT 13.4: Talk

Monday, March 20, 2017, 15:45–16:00, HSZ 103

Effects of enhanced electron correlations on upper critical field properties in AFe₂As₂ (A = K, Rb, and Cs) superconductors — •Seunghyun Khim^1,2, Dmitry Efremov¹, Anja U. B. Wolter¹, Sabine Wurmehl¹, and Bernd Büchner^1,3 — ¹Leibniz Institute for Solid State and Materials Research, Helmholtzstraße 20, 01069 Dresden, Germany — ²Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187, Dresden — ³Institute for Solid State Physics, TU Dresden, 01069 Dresden, Germany

Unusually large Sommerfeld coefficients (γ₀) in the stoichiometric AFe₂As₂ (A = K, Rb, and Cs) superconductors imply enhanced electron correlations which might be related to its unconventional pairing origin of superconductivity. Including experimental data from our CsFe₂As₂ single crystals, we summarize magnetic susceptibility and specific heat properties of the AFe₂As₂ series to clarify the impact of electron correlations on normal and superconducting states. Toward CsFe₂As₂, γ₀ increases to ∼ 160 mJ/mol K² and the broad local maximum in the magnetic susceptibility systematically shifts to lower temperatures. The slope of upper critical fields near T_c is also enhanced as predicted in accordance with the growing γ₀. Taking into account these observations, the effect of the enhanced correlations on superconductivity will be discussed together with the multiband nature, orbital-selective Mottness, and suggested quantum criticality.