Electronic structure of impurity-substituted Bi₂Sr ₂CaCu₂O_8+δ studied by angle-resolved photoemission spectroscopy

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on Co-, Ni-, and Zn-substituted Bi₂Sr₂CaCu ₂O_8+δ (Bi2212) to study the impurity effect on the electronic structure. The shape of Fermi surface and the symmetry of superconducting gap are unchanged by impurities, while the superconducting coherent peak around (π, 0) is remarkably suppressed. The temperature dependence of the coherent-peak intensity shows a good correspondence to the reported superfluid density. The intensity of coherent peak scales well with the T_c in pristine, Co-, and Ni-Bi2212, but not in Zn-Bi2212, suggesting that non-magnetic Zn atoms destroy the superconductivity more strongly than the magnetic impurities.