Effects of out-of-plane disorder on the nodal quasiparticle and superconducting gap in single-layer Bi$_2$Sr$_{1.6}Ln_{0.4}$CuO$_{6+\delta}$ ($Ln$ = La, Nd, Gd)

摘要

How out-of-plane disorder affects the electronic structure has beeninvestigated for the single-layer cupratesBi$_2$Sr$_{1.6}$$Ln$$_{0.4}$CuO$_{6+\delta}$ ($Ln$ = La, Nd, Gd) byangle-resolved photoemission spectroscopy. We have observed that, withincreasing disorder, while the Fermi surface shape and band dispersions are notaffected, the quasi-particle width increases, the anti-nodal gap is enhancedand the superconducting gap in the nodal region is depressed. The resultsindicate that the superconductivity is significantly depressed by out-of-planedisorder through the enhancement of the anti-nodal gap and the depression ofthe superconducting gap in the nodal region.