Doping dependence of chemical potential in Iron Pnictides by Photoemission

Recently superconductivity has been discovered in many iron pnictides when they are properly doped with charge carriers. It is important to study the chemical potential change as a function of charge carriers. We have performed a systematic photoemission study of core level shift and valence band as a function of doping. We will report our experimental results and comparisons to the first principal band calculations.