Doping evolution of Zhang-Rice singlet spectral weight: a comprehensive examination by x-ray absorption spectroscopy

TL;DR

This study uses x-ray absorption spectroscopy to analyze how the spectral weight of Zhang-Rice singlets evolves with doping in high-temperature superconductors, revealing deviations from simple models and confirming the singlet picture across doping levels.

Contribution

It provides a comprehensive experimental examination of doping dependence in spectral weight, challenging mean field predictions and supporting the robustness of the Zhang-Rice singlet model.

Findings

Spectral weight deviates from linear doping dependence.

Slope of spectral weight changes continuously with doping.

No saturation observed up to doping level p=0.23.

Abstract

The total spectral weight \textit{S} of the emergent low-energy quasipaticles in high-temperature superconductors is explored by x-ray absorption spectroscopy. In order to examine the applicability of the Hubbard model, regimes that cover from zero doping to overdoping are investigated. In contrast to mean field theory, we found that \textit{S} deviates from linear dependence on the doping level \textit{p}. The slope of \textit{S} versus \textit{p} changes continuously throughout the whole doping range with no sign of saturation up to \textit{p} = 0.23. Therefore, the picture of Zhang-Rice singlet remains intact within the most prominent doping regimes of HTSC's.