Doping-Dependent and Orbital-Dependent Band Renormalization in Ba(Fe1-xCox)2As2 Superconductors

Angle resolved photoemission spectroscopy of Ba(Fe 1- x Co x ) 2 As 2 ( x = 0.06, 0.14, and 0.24) shows that the width of the Fe 3 d y z / z x hole band depends on the doping level. In contrast, the Fe 3 d x 2 - y 2 and 3 z 2 - r 2 bands are rigid and shifted by the Co doping. The Fe 3 d y z / z x hole band is flattened at the optimal doping level x = 0.06, indicating that the band renormalization of the Fe 3 d y z / z x band correlates with the enhancement of the superconducting transition temperature. The orbital-dependent and doping-dependent band renormalization indicates that the fluctuations responsible for the superconductivity is deeply related to the Fe 3 d orbital degeneracy.