Far-infrared probe of superconductivity in SmO${}_{1-x}$F${}_x$FeAs}

Abstract

We report far-infrared reflectance measurements on polycrystalline superconducting samples of SmO${}_{1-x}$F${}_x$FeAs ($x$ = 0.12, 0.15 and 0.2). We clearly observe superconductivity induced changes of reflectivity in a broad range of energies, which resembles earlier optical measurements on high $T_c$ cuprates. The superconducting-to-normal reflectivity ratio $R_s/R_n$ grows for the photon energies below 18 meV and shows a complicated structure due to the presence of a strong infrared-active phonon at about 10 meV.

4 pages, 7 figures