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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity: Fe-based Superconductors - 122 Part 1

TT 8.6: Vortrag

Montag, 26. März 2012, 16:15–16:30, H 2053

Multigap superconductivity in (Ba,K)Fe₂As₂ probed by thermal expansion — •Anna Böhmer^1,2, Philipp Burger^1,2, Frédéric Hardy¹, Thomas Wolf¹, Peter Schweiss¹, Rainer Fromknecht¹, and Christoph Meingast¹ — ¹Institut für Festkörperphysik, Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe — ²Fakultät für Physik, Karlsruher Institut für Technologie, Postfach 6980, 76049 Karlsruhe

Hole doped (Ba,K)Fe₂As₂ is one of the most widely studied iron-based superconductors. Here, we report on an investigation of its thermal expansion using capacitive dilatometry. Overdoped samples, which do not undergo the magneto-structural transition, exhibit clear signatures of two-gap superconductivity in the thermal expansion coefficients. The data are analyzed with an extension of the two-gap alpha model, which is widely used to describe the specific heat of multi-band superconductors. By combining specific-heat and thermal-expansion data we are able to extract the uniaxial pressure dependence of T_c, of the gap magnitudes and of the electronic density of states. The influence of uniaxial pressure on the phase diagram is discussed.