Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 36: SC: Fe-based Superconductors - 122 - Properties, Electronic Structure, Mechanisms

TT 36.2: Talk

Wednesday, March 16, 2011, 14:15–14:30, HSZ 304

Thermodynamic investigations of the doping and pressure dependences of the electronic density of states and the superconducting gaps in the electron-doped iron pnictide Ba(Fe_1−xCo_x)₂As₂ — •Frédéric Hardy¹, Philipp Burger¹, Thomas Wolf¹, Peter Schweiss¹, Peter Adelmann¹, Doris Ernst¹, Robert A. Fisher², Robert Eder¹, Rolf Heid¹, Hilbert v. Löhneysen¹, and Christoph Meingast¹ — ¹Karlsruher Institut für Technologie, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — ²Lawrence Berkeley National Laboratory, Berkeley CA 94720. USA

Using specific-heat and high-resolution thermal-expansion measurements, we present an extensive study of the normal- and superconducting state properties of high-quality single crystals of the electron-doped iron pnictide Ba(Fe_1−xCo_x)₂As₂. We determine the evolution of the electronic density of states and superconducting gaps with Co-doping and pressure. Our measurements illustrate the competition between magnetism and superconductivity to monopolize the Fermi surface and also reveal the existence of large gapless contributions in strongly under- and over-doped conditions. These observations are discussed in terms of pair-breaking and changes of the electronic band structure, in line with recent theories.