Many-body correlations in quantum antiferromagnets: A microscopic coupled-cluster approach

Abstract
The coupled-cluster method of many-body theory is applied to anisotropic quantum antiferromagnets in one and two dimensions. It is found to give good results for ground-state and excited-state energies and the staggered magnetization. It also gives a qualitatively correct description of the entire one-dimensional Heisenberg-Ising phase and the phase change in one dimension as the anisotropy decreases.