Weak-coupling superconductivity in electron-doped NaFe0.95Co0.05As revealed by ARPES

We report a systematic study on the electronic structure and superconducting (SC) gaps in electron-doped NaFe0.95Co0.05As superconductor using angle-resolved photoemission spectroscopy. Holelike Fermi sheets are at the zone center and electronlike Fermi sheets are at the zone corner, and are mainly contributed by xz and yz orbital characters. Our results reveal a Delta/KBTc in the range of 1.8-2.1, suggesting a weak-coupling superconductivity in these compounds. Gap closing above the transition temperature (T-c) shows the absence of pseudogaps. Gap evolution with temperature follows the BCS gap equation near the Gamma, Z, and M high symmetry points. Furthermore, an almost isotropic superconductivity along the k(z) direction in the momentum space is observed by varying the excitation energies.