Spin fluctuations and high-temperature superconductivity in cuprates

TL;DR

This paper develops a microscopic theory for spin excitations and high-temperature superconductivity in cuprates, emphasizing the role of kinematical interactions arising from Hubbard operators within strongly correlated models.

Contribution

It introduces a consistent microscopic framework incorporating Hubbard operators to analyze spin excitations and superconductivity in cuprates, including effects of Coulomb repulsion and electron-phonon interactions.

Findings

Low-energy spin excitations modeled by the t-J model.

Electronic properties studied with an extended Hubbard model.

Kinematical interactions significantly influence superconductivity.

Abstract

To describe the cuprate superconductors, models of strongly correlated electronic systems, such as the Hubbard or t-J models, are commonly employed. To study these models, projected (Hubbard) operators have to be used. Due to the unconventional commutation relations for the Hubbard operators, a specific kinematical interaction of electrons with spin and charge fluctuations emerges. The interaction is induced by the intraband hopping with a coupling parameter of the order of the kinetic energy of electrons W which is much larger than the antiferromagnetic exchange interaction J induced by the interband hopping. This review presents a consistent microscopic theory of spin excitations and superconductivity for cuprates where these interactions are taken into account within the Hubbard operator technique. The low-energy spin excitations are considered for the t-J model, while the electronic properties are studied using the two-subband extended Hubbard model where the intersite Coulomb repulsion V and electron-phonon interaction are taken into account.