The bulge in the basal plane area of cuprate superconductors - evidence for 3a singlet hole pairs

TL;DR

This paper presents evidence that the bulge in the basal plane area of cuprate superconductors is linked to 3a singlet hole pairs forming filamentary structures, which influence the pseudogap regime and optimal doping.

Contribution

It introduces a novel connection between lattice geometry, hole pairing, and the pseudogap phase in cuprates, highlighting the role of 3a hole pairs.

Findings

Bulge correlates with non-double-occupancy constraint.

Formation of 3a hole pairs creates a nodal metal in the pseudogap regime.

Optimal doping occurs at approximately 0.16 hole concentration.

Abstract

The bulge in the doping dependence of the basal plane area in hole doped cuprate superconductors is connected with a non-double-occupancy constraint for the oxygen cages in the CuO_2 lattice. This constraint favors the formation of 3a hole pairs growing to filaments with gapless excitations along the (pi, pi) direction. Thus in the pseudogap regime a nodal metal of hole pairs is created. Densest packed 3a hole pairs stabilize the optimum doped state at n =1/6 ~ 0.16.