Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.3: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Isovalent substitution on the iron site in pnictides - an optical study — •Daniel Pröpper1, Aliaksei Charnukha1, Ma Jin Eom2, Jun Sung Kim2, Bernhard Keimer1, and Alexander Boris1 — 1Max-Planck-Institute for Solid State Research, Stuttgart, Germany — 2Department of Physics, Pohang University of Science and Technology, Pohang, Korea
Here we report on the full complex dielectric function є(ω) in the ab plane of Ba(Fe1−xRux)2As2 applying spectroscopic ellipsometry in the broad range of 60 meV to 6 eV. The investigated set of samples spans the whole range from the parent compound BaFe2As2 deep into the overdoped regime (x = 0.74), not reported so far, showing superconductivity with Tc up to 20 K at optimally doping (x = 0.35). By classical dispersion analysis of Drude-Lorentz type we detect an increase in the bare plasma frequency ωp, associated with the free carrier response, and a significant decrease of the low-energy dielectric permittivity є∞ upon doping. The main contribution to є∞ arises from the lowest lying interband transitions at ∼ 0.5 eV, assigned to be from Fe(Ru)-d/As-p to Fe(Ru)-d hybrid states [1]. This gives rise to anomalously high є∞≈ 60 − 80 among all other high-Tc superconductors. This, in conjunction with increased Fe(Ru)-d bandwidth with x due to stronger hybridization with As-p states [2], hints to a strong decrease in the high polarizability of Fe-As bonds, which is thought to play a crucial role in establishing and controlling superconductivity in iron pnictides.
A. Charnukha et al., Nat. Comm. 2 (2011), 219
L. Zhang et al., PRB 79 (2009), 174530