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)

TL;DR

This study investigates how out-of-plane disorder in single-layer cuprates influences electronic properties, revealing increased quasiparticle scattering, enhanced anti-nodal gaps, and suppressed superconducting gaps, thereby weakening superconductivity.

Contribution

It provides direct experimental evidence on the effects of out-of-plane disorder on the electronic structure and superconductivity in single-layer cuprates using ARPES.

Findings

Quasiparticle width increases with disorder

Anti-nodal gap is enhanced by disorder

Superconducting gap in the nodal region is depressed

Abstract

How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi$_2$Sr$_{1.6}$$Ln$$_{0.4}$CuO$_{6+\delta}$ ($Ln$ = La, Nd, 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 quasi-particle width increases, the anti-nodal 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 anti-nodal gap and the depression of the superconducting gap in the nodal region.