Low Energy Electronic Structures in Electron-Doped and Hole-Doped Superconducting (Ba/K)(Fe/Co)2As2

Systematic high resolution angle-resolved photoemission spectroscopic studies have been performed on the optimally electron-doped BaFe1.82Co0.18As2 (T-c = 24 K) and hole-doped Ba0.6K0.4Fe2As2 (T-c = 37 K) superconductors. The superconducting gap is nearly isotropic in momentum space. Utilizing different experimental geometries, the detailed electronic band structures were determined experimentally and compared with first principle LDA calculations. The overall bandwidth is reduced by a factor of 2. However, the low energy quasiparticle dispersions near zone corner exhibit stronger renormalization by a factor of 4-5, k(z) dependence was observed on the electron pockets at zone corner.