Observation of an isotropic superconducting gap at the Brillouin zone center of Tl${}_{0.63}$K${}_{0.37}$Fe${}_{1.78}$Se${}_2$

X. -P. Wang, P. Richard, A. van Roekeghem +10

We performed a high-resolution angle-resolved photoemission spectroscopy study on superconducting (SC) Tl${}_{0.63}$K${}_{0.37}$Fe${}_{1.78}$Se${}_2$ ($T_c=29$ K) in the whole Brillouin zo…