Coupled-cluster calculations for the ground- and excited-states of the spin-half XXZ model

TL;DR

This paper applies coupled-cluster calculations to the spin-1/2 XXZ model, improving ground-state and excitation predictions by including higher-order correlations, and validating results against other advanced methods.

Contribution

It introduces a coupled-cluster approximation with both two-body and four-body correlations for the XXZ model, enhancing accuracy over previous methods.

Findings

Improved ground-state energy estimates.

Enhanced sublattice magnetization calculations.

Accurate excitation spectrum matching other methods.

Abstract

The coupled-cluster method is applied to the spin-1/2 antiferromagnetic XXZ model on a square lattice by employing an approximation which contains two-body long-range correlations and high-order four-body local correlations. Improvement is found for the ground-state energy, sublattice magnetization, and the critical anisotropy when comparing with the approximation including the two-body correlations alone. We also obtain the full excitation spectrum which is in good agreement with the quantum Monte Carlo results and the high-order spin-wave theory.