Phase Transition Of The SpinOne SquareLattice Anisotropic Heisenberg Model
Abstract
The coupled cluster method (CCM) is applied to the spinone anisotropic Heisenberg antiferromagnet (HAF) on the square lattice at zero temperature using a new highorder CCM groundstate formalism for general quantum spin number ($s \ge 1/2$). The results presented constitute the first such application of this new formalism, and they are shown to be among the most accurate results for the groundstate energy and sublattice magnetisation of this model as yet determined. We ``track'' the solution to the CCM equations at a given level of approximation with respect to the anisotropy parameter, $\Delta$, from the trivial Ising limit ($\Delta \to \infty$) down to a critical value $\Delta_c$, at which point this solution terminates. This behaviour is associated with a phase transition in the system, and hence a primary result of these highorder CCM calculations is that they provide an accurate and unbiased (i.e., {\it ab initio}) estimation of the position of the quantum phase transition point as a function of the anisotropy parameter. Our result is, namely, that this point occurs at (or slightly below) the isotropic Heisenberg point at $\Delta=1$, for this model.
 Publication:

arXiv eprints
 Pub Date:
 March 2001
 arXiv:
 arXiv:condmat/0103321
 Bibcode:
 2001cond.mat..3321F
 Keywords:

 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 4 pages, 2 figures