Why phase diagrams of different underdoped cuprates are remarkably different? Disorder versus bilayer

TL;DR

This paper investigates why the phase diagrams of two underdoped cuprates, LSCO and YBCO, differ significantly, emphasizing the roles of disorder and bilayer structure in their magnetic and electronic properties.

Contribution

It introduces an approach that explains the contrasting magnetic and spin ordering behaviors by highlighting the importance of bilayer structure and disorder effects.

Findings

YBCO's properties are unaffected by disorder, emphasizing bilayer importance.

LSCO's properties are largely driven by intrinsic disorder.

Superconductivity is closely linked to incommensurate spin ordering.

Abstract

Contrary to a widely accepted view the phase diagrams of La$_{2-x}$Sr$_x$CuO$_4$ and YBa$_2$Cu$_3$O$\rm_{6+y}$, in spite of similarities are remarkably different. Both the electric conduction properties and the commensurate/incommensurate spin ordering properties differ dramatically. It is argued that the role of disorder in YBCO is insignificant while the bilayer structure is crucial. On the other hand in LSCO the intrinsic disorder to a large extent drives the properties of the system. The developed approach explains the low-temperature magnetic properties of the systems. The most important point is the difference with respect to the incommensurate spin ordering, including the difference in the incommensurate pitches. The present analysis demonstrates that the superconductivity is intimately related to the incommensurate spin ordering.