1107.0599 (Mohammad Merdan et al.)

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

Mohammad Merdan, Y. Xian

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.

View original: http://arxiv.org/abs/1107.0599