Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

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

TT 8.5: Talk

Monday, March 26, 2012, 16:00–16:15, H 2053

Universal microscopic description of the infrared conductivity of 122 iron arsenides — •Aliaksei Charnukha¹, Oleg V. Dolgov¹, Alexander A. Golubov², Yulia Matiks¹, Dun Lu Sun¹, Cheng Tian Lin¹, Bernhard Keimer¹, and Alexander V. Boris¹ — ¹Max-Planck-Institut für Festköorperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany — ²Faculty of Science and Technology and MESA+ Institute of Nanotechnology, NL-7500 AE Enschede, The Netherlands

We report the full complex dielectric function of high-purity Ba_0.68K_0.32Fe₂As₂ single crystals with T_c=38.5 K determined by wide-band spectroscopic ellipsometry at temperatures 10 K≤ T≤ 300 K. We discuss the microscopic origin of superconductivity-induced infrared optical anomalies in the framework of a multiband Eliashberg theory with two distinct superconducting gap energies 2Δ_A=6 k_B T_c and 2Δ_B=2.2 k_B T_c. The observed unusual suppression of the optical conductivity in the superconducting state at energies up to 14 k_B T_c can be ascribed to spin-fluctuation–assisted processes in the clean limit of the strong-coupling regime. We further demonstrate that the same model provides a good description of the infrared conductivity of electron-doped compounds in this class of superconductors.