We report the full complex dielectric function of high-purity Ba0.68K0.32Fe2As2 single crystals with Tc=38.5K determined by wideband spectroscopic ellipsometry at temperatures 10≤T≤300K. 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, 2ΔA≈6kBTc and 2ΔB≈2.2kBTc. The observed unusual suppression of the optical conductivity in the superconducting state at energies up to 14kBTc can be ascribed to spin-fluctuation–assisted processes in the clean limit of the strong-coupling regime.
|Number of pages||7|
|Journal||Physical review B: Condensed matter and materials physics|
|Publication status||Published - 2011|