Zn-substitution effects on the low-energy quasiparticles in Bi₂Sr₂CaCu₂O_8+δ studied by angle-resolved photoemission spectroscopy

We have performed high-resolution angle-resolved photoemission spectroscopy on Bi₂Sr₂Ca(Cu_1-xZn_x)₂O_8+δ (x = 0.0, 0.05) to study the Zn-substitution effects on the low-energy quasiparticles. We found that the Zn substitution causes the reduction of the quasiparticle intensity and the superconducting gap, while it does not affect the normal-state band dispersion, the Fermi surface, or the quasiparticle lifetime. This indicates that the Zn substitution locally destroys or hinders the superconducting pairing and as a result decreases the superfluid density, but does not affect the long-range coherence among quasiparticles.