4 papers
High-Order Coupled Cluster Method Calculations for the Ground- and Excited-State Properties of the Spin-Half XXZ Model
R. F. Bishop, D. J. J. Farnell, S. E. Krueger +3
In this article, we present new results of high-order coupled cluster method (CCM) calculations, based on a Néel model state with spins aligned in the -direction, for both the g…
Sign Rules for Anisotropic Quantum Spin Systems
R. F. Bishop, D. J. J. Farnell, J. B. Parkinson
We present new and exact ``sign rules'' for various spin-s anisotropic spin-lattice models. It is shown that, after a simple transformation which utilizes these sign rules, the gro…
Phase Transitions in the Spin-Half J_1--J_2 Model
Raymond F. Bishop, Damian J. J. Farnell, John B. Parkinson
The coupled cluster method (CCM) is a well-known method of quantum many-body theory, and here we present an application of the CCM to the spin-half J_1--J_2 quantum spin model with…
Coupled Cluster Treatment of the XY model
D. J. J. Farnell, S. E. Krueger, J. B. Parkinson
We study quantum spin systems in the 1D, 2D square and 3D cubic lattices with nearest-neighbour XY exchange. We use the coupled-cluster method (CCM) to calculate the ground-state e…