Superlattice origin of incommensurable density waves in La_{2-x}Ae_xCuO4 (Ae = Ba, Sr)

TL;DR

This paper explains the origin of incommensurable density waves in La_{2-x}Ae_xCuO4 using a superlattice model, linking doping levels to magnetic and charge density wave incommensurability, supported by experimental data.

Contribution

It introduces a superlattice-based explanation for incommensurable density waves in cuprates, aligning theoretical predictions with experimental observations.

Findings

Derived formula for incommensurability delta(x) matches experimental data.

Incommensurate density waves originate from superlattice structures.

Doping influences magnetic and charge density wave relationships.

Abstract

In line with the Coulomb-oscillator model of superconductivity, loop currents of excited 3s electrons from O^2- ions, passing in the CuO2 plane through nuclei of nearest-neighbor oxygen quartets, create the antiferromagnetic phase of undoped copper oxides. Holes, introduced by alkaline-earth doping of La2CuO4, destroy the loop currents, thereby weakening antiferromagnetism until it disappears at doping x = 0.02. Further doping of La_2-xAe_xCuO4 gives rise to incommensurate free-hole density waves whose wavelength is determined by the spacing of a doping superlattice. Modulating the ordering of the ions' magnetic moments, the charge-density wave, of incommensurability 2 delta, causes a magnetic density wave of incommensurability delta. The formula derived for delta(x) is in excellent agreement with data from X-ray diffraction and neutron scattering.