Effect of Zn impurities on the electronic structure of La1.85 Sr0.15 Cu O4 studied by high-resolution angle-resolved photoemission spectroscopy

High-resolution angle-resolved photoemission spectroscopy has been performed on Zn-substituted La1.85 Sr0.15 Cu O4 to study the impurity effect on the electronic structure near the Fermi level. Upon Zn substitution, the kink in the band dispersion at 20 meV and the coherence peak in the off-nodal region in the superconducting state are significantly weakened and, at the same time, additional electronic states systematically evolve inside the superconducting gap. The suppression of the kink with Zn substitution shows a good correspondence to the low-energy incommensurate magnetic excitations.