Systematic Inclusion of High-Order Multi-Spin Correlations for the Spin-$1\over2$ $XXZ$ Models

TL;DR

This paper employs a systematic coupled-cluster method to accurately analyze ground-state properties and quantum critical behavior of spin-1/2 XXZ models on 1D and 2D lattices, including high-order multi-spin correlations.

Contribution

It introduces a high-order ab initio coupled-cluster approach for XXZ models, enabling detailed analysis of quantum criticality with improved accuracy.

Findings

High-accuracy ground-state properties across anisotropy parameters

Systematic study of quantum critical behavior

Inclusion of high-order multi-spin correlations

Abstract

We apply the microscopic coupled-cluster method (CCM) to the spin-$1\over2$ $XXZ$ models on both the one-dimensional chain and the two-dimensional square lattice. Based on a systematic approximation scheme of the CCM developed by us previously, we carry out high-order {\it ab initio} calculations using computer-algebraic techniques. The ground-state properties of the models are obtained with high accuracy as functions of the anisotropy parameter. Furthermore, our CCM analysis enables us to study their quantum critical behavior in a systematic and unbiased manner.