Abstract
We performed a laser angle-resolved photoemission spectroscopy (ARPES) study on a wide doping range of Ba${}_{1\ensuremath{-}x}$K${}_{x}$Fe${}_{2}$As${}_{2}$ (BaK) and precisely determined the doping evolution of the superconducting gaps in this compound. The gap size of the outer hole Fermi-surface (FS) sheet around the Brillouin zone (BZ) center shows an abrupt drop with overdoping (for $x\ensuremath{\gtrsim}$ 0.6) while the inner and middle FS gaps roughly scale with ${T}_{c}$. This is accompanied by the simultaneous disappearance of the electron FS sheet with similar orbital character at the BZ corner. These results indicate the different contributions of ${X}^{2}\ensuremath{-}{Y}^{2}$ and $XZ/YZ$ orbitals to superconductivity in BaK and can hardly be completely reproduced by the available theories on iron-based superconductors.
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