Failure of t-J models in describing doping evolution of spectral weight in x-ray scattering, optical and photoemission spectra of the cuprates

TL;DR

This paper demonstrates that the traditional t-J models fail to accurately describe the doping-dependent spectral weight transfer in cuprates, highlighting the importance of an intermediate coupling scenario with a doping-dependent effective Hubbard U.

Contribution

The study provides experimental evidence that challenges the fixed-U assumption in t-J models, proposing a doping-dependent effective U to better explain spectral weight transfer in cuprates.

Findings

Spectral weight transfer occurs faster than large U-limit predictions.

Experimental spectra are inconsistent with fixed-U models.

Intermediate coupling with doping-dependent U explains observations.

Abstract

We have analyzed experimental evidence for an anomalous transfer of spectral weight from high to low energy scales in both electron and hole doped cuprates as a function of doping. X-ray scattering, optical and photoemission spectra are all found to show that the high energy spectral weight decreases with increasing doping at a rate much faster than predictions of the large $U-$limit calculations. The observed doping evolution is however well-described by an intermediate coupling scenario where the effective Hubbard $U$ is comparable to the bandwidth. The experimental spectra across various spectroscopies are inconsistent with fixed-$U$ exact diagonalization or quantum Monte Carlo calculations, and suggest a significant doping dependence of the effective $U$ in the cuprates.