Optical Spectroscopy of BaFe$_{1.8}$Co$_{0.2}$As$_{2}$ in the normal state

Sefat et al.[1] have found that electron doping of the iron arsenide BaFe$_{2}$As$_{2}$ by cobalt doping of the iron site induces superconductivity, as high as 38K. We will report a comprehensive optical spectroscopy study of normal state BaFe$_{1.8}$Co$_{0.2}$As$_{2}$ (Tc = 22K) over a wide range of frequencies from 50 to 40,000 cm$^{-1}$ and temperatures. Measuring the reflectance of single crystal samples we acquire a spectra from which we will show the optical conductivity and the dielectric function. Using Eliashberg formalism we determine the electron boson spectral function. [1] A.S. Sefat et al., Phys. Rev.Lett. 101, 117004 (2008)