Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 31: Superconductivity: Fe-based Superconductors – 122 and 111
TT 31.7: Vortrag
Dienstag, 17. März 2015, 11:30–11:45, H 2053
A calorimetric investigation of RbFe2As2 single crystals — •Seunghyun Khim1, Saicharan Aswartham1, Vadim Grinenko1, Christian C. F. Blum1, Frank Steckel1, Daniel Gruner1, Anja U. B. Wolter1, Christian Hess1, Stefan-Ludwig Drechsler1, Bernd Büchner1,2, and Sabine Wurmehl1,2 — 1Leibniz Institute for Solid State and Materials Research, Helmholtzstrasse 20, 01069 Dresden, Germany — 2Institute for Solid State Physics, TU Dresden, 01069 Dresden, Germany
We present physical properties of single crystals of the iron pnictide superconductor RbFe2As2 grown by a self-flux method. A bulk superconducting transition at Tc ∼ 2.7 K was consistently observed in resistivity, magnetic susceptibility and specific heat measurements. While the normal state resistivity following a T2 dependence at low T is that of a conventional metal, the magnetic susceptibility shows a deviation from a conventional Curie-Weiss behavior and an unusual broad local maximum around 80 K. Similar humps have been observed for KFe2As2 and SrCo2As2. A large Sommerfeld coefficient, γ0 = 127 mJ/mol K2, was observed seemingly a common feature of heavily hole-doped 122 pnictides. We analyze the superconducting transition seen in our specific heat data by using the s-wave BCS two-gap model. The presence of a small gap is discussed as possible explanation to account for the large specific heat contribution far below Tc. The large Hc2 anisotropy ratio, Γ = Hc2ab/Hc2c ∼ 7 near Tc is also discussed within this multiband nature of the Fermi surface.