Influence of apical oxygen on the extent of in-plane exchange interaction in cuprate superconductors

TL;DR

This study investigates how apical oxygen atoms influence the in-plane exchange interactions in cuprate superconductors, revealing that their absence extends the hopping range and affects magnetic properties, which may impact superconductivity.

Contribution

It provides a comparative analysis of magnetic spectra in different cuprates, linking apical oxygen presence to the extent of exchange interactions and magnetic network dimensionality.

Findings

Absence of apical oxygens increases in-plane hopping range.

CaCuO2 exhibits a 3D exchange-bond network due to no apical oxygens.

Crystal structure influences magnetic exchange interactions.

Abstract

In high Tc superconductors the magnetic and electronic properties are determined by the probability that valence electrons virtually jump from site to site in the CuO2 planes, a mechanism opposed by on-site Coulomb repulsion and favored by hopping integrals. The spatial extent of the latter is related to transport properties, including superconductivity, and to the dispersion relation of spin excitations (magnons). Here, for three antiferromagnetic parent compounds (single-layer Bi2Sr0.99La1.1CuO6+delta, double-layer Nd1.2Ba1.8Cu3O6 and infinite-layer CaCuO2) differing by the number of apical atoms, we compare the magnetic spectra measured by resonant inelastic x-ray scattering over a significant portion of the reciprocal space and with unprecedented accuracy. We observe that the absence of apical oxygens increases the in-plane hopping range and, in CaCuO2, it leads to a genuine 3D exchange-bond network. These results establish a corresponding relation between the exchange interactions and the crystal structure, and provide fresh insight into the materials dependence of the superconducting transition temperature.