Nonlocal Excitations and 1/8 Singularity in Cuprates

TL;DR

This study uses a self-consistent projection operator method to analyze the momentum-dependent excitation spectra of the 2D Hubbard model, revealing nonlocal effects of electron correlations and their influence on the critical doping level related to stripe instabilities.

Contribution

It demonstrates how nonlocal excitations and antiferromagnetic correlations affect spectral features and the critical doping concentration in the Hubbard model.

Findings

Intersite antiferromagnetic correlations cause shadow bands.

Nonlocal excitations shift the critical doping from 0.153 to 0.123.

The shift suggests possible stripe instability at 1/8 doping.

Abstract

Momentum-dependent excitation spectra of the two-dimensional Hubbard model on the square lattice have been investigated at zero temperature on the basis of the full self-consistent projection operator method in order to clarify nonlocal effects of electron correlations on the spectra. It is found that intersite antiferromagnetic correlations cause shadow bands and enhance the Mott-Hubbard splittings near the half-filling. Furthermore nonlocal excitations are shown to move the critical doping concentration $\delta^{\ast}_{h}$, at which the singular quasiparticle peak is located just on the Fermi level, from $\delta^{\ast}_{h}=0.153$ (the single-site value) to $\delta^{\ast}_{h}=0.123$. The latter suggests the occurance of an instability such as the stripe at $\delta^{\ast}_{h}=1/8$.