High-order coupled cluster method calculations for the ground- and excited-state properties of the spin-half XXZ model

Bishop, R. F., Farnell, Damian J. J. ORCID: https://orcid.org/0000-0003-0662-1927, Kruger, S. E., Parkinson, J. B., Richter, J. and Zeng, C. 2000. High-order coupled cluster method calculations for the ground- and excited-state properties of the spin-half XXZ model. Journal of Physics: Condensed Matter 12 (30) , pp. 6887-6902. 10.1088/0953-8984/12/30/317

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Abstract

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 z-direction, for both the ground- and excited-state properties of the spin-half XXZ model on the linear chain, the square lattice, and the simple cubic lattice. In particular, the high-order CCM formalism is extended to treat the excited states of lattice quantum spin systems for the first time. Completely new results for the excitation energy gap of the spin-half XXZ model for these lattices are thus determined. These high-order calculations are based on a localized approximation scheme called the LSUBm scheme in which we retain all k-body correlations defined on all possible locales of m adjacent lattice sites (k≤m). The `raw' CCM LSUBm results are seen to provide very good results for the ground-state energy, sublattice magnetization, and the value of the lowest-lying excitation energy for each of these systems. However, in order to obtain even better results, two types of scheme for extrapolating the LSUBm results to the limit m→∞ (i.e., the exact solution in the thermodynamic limit) are presented. The extrapolated results provide extremely accurate results for the ground- and excited-state properties of these systems across a wide range of values of the anisotropy parameter.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Dentistry
Subjects:	Q Science > QC Physics
Publisher:	IOP Publishing
ISSN:	0953-8984
Last Modified:	04 Jan 2024 08:40
URI:	https://orca.cardiff.ac.uk/id/eprint/64288

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