paper

Collective spin and charge excitations in the -- model of high- cuprates

arXiv:2107.02152 · doi:10.1016/j.jmmm.2021.168395

Abstract

The -- model of high- copper-oxide superconductors incorporates both the on-site Coulomb repulsion and kinetic exchange interaction and yields a semi-quantitative description of the static properties of those materials. We extend this analysis to dynamic quantities and address collective spin- and charge excitations in the correlated metallic state of the -- model. We employ VWF+ approach that combines the variational wave function (VWF) approach with the expansion in the inverse number of fermionic flavors (). It is shown that the resonant (paramagnon) contribution to the dynamic magnetic susceptibility remains robust as one interpolates between the Hubbard- and --model limits, whereas the incoherent continuum undergoes substantial renormalization. Energy of the collective charge mode diminishes as the strong-coupling limit is approached. We also introduce the concept of effective kinetic exchange interaction that allows for a unified interpretation of magnetic dynamics in the Hubbard, -, and -- models. The results are discussed in the context of recent resonant inelastic -ray scattering experiments for the high- cuprates.

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