Fermi surface and superconducting gap of Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ studied by high-resolution ARPES

The electronic states near the Fermi level are the key ingredient to understand the superconducting mechanism of iron-based superconductor. Although electrons in the iron orbitals have been found to play a key role to the occurrence of the superconductivity, the microscopic origin of high-$T_{c}$ superconductivity is still unclear. To address this important issue, we report our recent high-resolution ARPES results on hole-doped Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$, and demonstrate the Fermi-surface-sheet and momentum dependence of the superconducting gap as well as the doping evolution of the Fermi surface and band structure.