Intraplanar couplings in the CuO_2 lattice of cuprate superconductors

TL;DR

This study examines how doping affects the structural properties of cuprate superconductors, revealing a 'bulge' in basal area around optimal doping linked to strong electronic correlations in the CuO_2 lattice.

Contribution

It provides new insights into the doping-dependent structural behavior of cuprates, highlighting the role of quantum liquid effects on lattice compressibility.

Findings

Basal areas shrink with hole doping but show a bulge at optimal doping.

The bulge is attributed to strongly correlated quantum liquid effects.

Inhomogeneous doping cannot explain the observed anomaly.

Abstract

We have investigated the doping dependencies of the basal areas in single-layer high-T_c cuprates La_{2-x}Sr_xCuO_4 and HgBa_2CuO_x, as well as in two-layer Y_{1-y}Ca_yBa_2Cu_3O_x and HgBa_2CaCu_2O_x. The basal areas not only tend to shrink on hole doping, as expected from single electron quantum chemistry, but exhibit also a "bulge'' around optimum doping. We attribute the "bulge'' to the effects of the strongly correlated quantum liquid on the CuO_2 lattice, rendering it nearly incompressible around optimum doping, but highly compressible in the weakly overdoped regime. Inhomogenous doping cannot account for this anomaly in the electronic compressibility of the CuO_2 lattice.