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Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: Superconductivity: Fe-based Superconductors - 122

TT 27.8: Talk

Tuesday, March 12, 2013, 11:45–12:00, H18

Pressure dependencies and first-order transition in KFe2As2 — •Philipp Burger1,2, Anna Böhmer1,2, Frédéric Hardy1, Thomas Wolf1, Peter Schweiss1, Rainer Fromknecht1, and Christoph Meingast11Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany — 2Fakultät für Physik, Karlsruher Institut für Technologie, 76128 Karlsruhe, Germany

Here we present a thermodynamic study on KFe2As2 single crystals (Tc=3.4 K) using high-resolution thermal-expansion, specific heat, magnetostriction and magnetization measurements. From these measurements we extract the uniaxial pressure dependencies of the Sommerfeld coefficient γ, the critical temperature Tc, the upper critical field Hc2, the magnetic susceptibility χ and the thermodynamical critical field Hc. Interestingly, the normalized pressure derivatives of Tc and Hc are about a factor of 10 larger than the pressure dependence of gamma, clearly showing that Tc is not closely correlated with γ. In particular the pressure dependencies of Tc show a very anisotropic behavior for the two different directions. Similar anisotropic behavior is also observed for Hc2 and Hc indicating that they are strongly coupled to each other.

In addition, magnetostriction and magnetization data for H parallel a-axis show that the superconducting transition is changing from second-order to first-order around 2 K. These results support that the upper critical field Hc2 is strongly suppressed via Pauli paramagnetism.

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