Fermi arc in the superconducting state of impurity-doped Bi2 Sr2 CaCu2 O8

We have performed ultrahigh energy- and momentum-resolved angle-resolved photoemission spectroscopy of impurity-doped Bi2 Sr2 CaCu2 O8. We found that the point node of the superconducting gap near the (π/2,π/2) point in a pristine sample gradually evolves into a small gapless Fermi arc upon Zn or Ni doping. The shape of impurity-induced density of states inside the superconducting gap shows a marked difference between Zn and Ni doping, demonstrating that the low-energy excitation properties are strongly sensitive to the character of impurities.