Bethe-Salpeter equations for the collective modes of the $t-U-V-J$ model with d-wave pairing

TL;DR

This paper uses Bethe-Salpeter equations to analyze collective modes in a $t$-$U$-$V$-$J$ model, explaining the neutron scattering resonance peak in cuprates as a spin exciton with specific interaction parameters.

Contribution

It introduces a detailed Bethe-Salpeter framework for the $t$-$U$-$V$-$J$ model to explain the resonance peak as a spin exciton in cuprates.

Findings

Resonance peak at 40 meV in Bi2212 explained as a spin exciton.

Calculated energy of the lowest mode vs. interaction parameters.

Identified $UJ$ lines consistent with ARPES data.

Abstract

The Bethe-Salpeter equations for the collective modes of a $t$-$U$-$V$-$J$ model are used to analyze the resonance peak observed at $\bf{Q}=(\pi,\pi)$ in neutron scattering experiments on the cuprates. We assume that the resonance emerges due to the mixing between the spin channel and 19 other channels. We have calculated the energy of the lowest mode of the extended Hubbard model ($J=0$) vs the on-site repulsive interaction $U$, as well as the $UJ$ lines in the interaction parameter space which are consistent with the ARPES data and reproduces the resonance peak at 40 meV in Bi2212 compound. We find that the resonance is predominantly a spin exciton.