Superconductivity and incommensurate spin fluctuations in a generalized t-J model for the cuprates

TL;DR

This paper models cuprate superconductors using a generalized t-J model derived from the three-band Hubbard Hamiltonian, revealing d+s superconductivity and incommensurate spin fluctuations consistent with experimental observations.

Contribution

It introduces a systematic low-energy reduction of the three-band Hubbard model incorporating a three-site term, and demonstrates its mean-field solution exhibits realistic superconducting and magnetic properties.

Findings

Predominantly d_{x^2-y^2} superconductivity with doping dependence matching experiments.

Incommensurate peaks in spin structure factor near $ ext{wave vectors}$ consistent with observations.

Model parameters close to realistic cuprate values produce experimental-like results.

Abstract

We consider the slave-fermion Schwinger-boson decomposition of an effective model obtained through a systematic low-energy reduction of the three-band Hubbard Hamiltonian. The model includes a three-site term t'' similar to that obtained in the large-U limit of the Hubbard model but of opposite sign for realistic or large O-O hopping. For parameters close to the most realistic ones for the cuprates, the mean-field solution exhibits d+s superconductivity (predominantly d_{x^2-y^2}) with a dependence on doping x very similar to the experimentally observed. We also obtained incommensurate peaks at wave vectors near $\pi (1,1 +(-) 2x)$ in the spin structure factor, which also agree with experiment.