Generic character of charge and spin density waves in superconducting cuprates

TL;DR

This study reveals that charge density waves in cuprate superconductors exhibit a generic behavior with doping, characterized by temperature-independent amplitude and a non-monotonic wavevector, indicating a common underlying mechanism.

Contribution

The paper demonstrates a universal behavior of charge density waves in cuprates through combined scattering techniques and a Landau-Ginzburg model, unifying understanding across different materials.

Findings

CDW amplitude is temperature-independent and develops above accessible temperatures.

The CDW wavevector shows a non-monotonic temperature dependence.

High-temperature wavevector decreases with doping, similar to YBa2Cu3O6+δ.

Abstract

Understanding the nature of charge density waves (CDW) in cuprate superconductors has been complicated by material specific differences. A striking example is the opposite doping dependence of the CDW ordering wavevector in La-based and Y-based compounds, the two families where charge ordering is strongest and best characterized. Here we report a combined resonant soft X-ray scattering (RSXS) and neutron scattering study of charge and spin density waves in isotopically enriched La$_{1.8-x}$ Eu$_{0.2}$ Sr$_{x}$ CuO$_{4}$ over a range of doping $0.07 \leq x \leq 0.20$. For all dopings studied by RSXS, we find that the CDW amplitude is approximately temperature-independent and develops well above experimentally accessible temperatures. Surprisingly, the CDW ordering wavevector shows a non-monotonic temperature dependence, with a sudden change occurring at temperatures near the SDW onset temperature. We describe this behavior with a Landau-Ginzburg theory for an incommensurate CDW in a metallic system with a finite charge compressibility and CDW-SDW coupling. Our Landau-Ginzburg analysis suggests that the ordering wavevector at high temperatures decreases with increased doping. This behavior is opposite to the trend at low temperatures and highly reminiscent of the doping dependence seen in YBa$_2$ Cu$_3$ O$_{6+\delta}$ , suggesting a common origin of the CDW in hole-doped cuprate superconductors.