A weak-coupling superconductivity in the electron doped   NaFe$_{0.95}$Co$_{0.05}$As is revealed by ARPES
  We report a systematic study on the electronic structure and superconducting (SC) gaps in electron doped NaFe$_{0.95}$Co$_{0.05}$As superconductor using angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the zone center and electron-like Fermi sheets are at the zone corner, and are mainly contributed by $xz$ and $yz$ orbital characters. Our results reveal a $\frac{\Delta}{K_B T_c}$ 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 follow the BCS gap equation near the $\Gamma$, $Z$, and $M$ high symmetry points. Furthermore, an almost isotropic superconductivity along $k_z$ direction in the momentum space is observed by varying the excitation energies. 
S. Thirupathaiah, D. V. Evtushinsky, J. Maletz, V. B. Zabolotnyy, A.   A. Kordyuk, T. K. Kim, S. Wurmehl, M. Roslova, I. Mor...
cond-mat.supr-con