How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates ${\text{Bi}}_2{\text{Sr}}_{1.6}{L}_{0.4}{\text{CuO}}_{6+\delta }$ ($L=\text{La}$, Nd, and Gd) by angle-resolved photoemission spectroscopy. We have observed that, with increasing disorder, while the Fermi-surface shape and band dispersions are not affected, the quasiparticle width increases, the antinodal gap is enhanced and the superconducting gap in the nodal region is depressed. The results indicate that the superconductivity is significantly depressed by out-of-plane disorder through the enhancement of the antinodal gap and the depression of the superconducting gap in the nodal region.

• Received 11 July 2008

DOI:https://doi.org/10.1103/PhysRevB.79.144517