Coupled cluster method calculations of quantum magnets with spins of general spin quantum number

Farnell, Damian J. J. ORCID: https://orcid.org/0000-0003-0662-1927, Bishop, R. F. and Gernoth, K. A. 2002. Coupled cluster method calculations of quantum magnets with spins of general spin quantum number. Journal of Statistical Physics 108 (3-4) , pp. 401-428. 10.1023/A:1015769622279

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Abstract

We present a new high-order coupled cluster method (CCM) formalism for the ground states of lattice quantum spin systems for general spin quantum number, s. This new “general-s” formalism is found to be highly suitable for a computational implementation, and the technical details of this implementation are given. To illustrate our new formalism we perform high-order CCM calculations for the one-dimensional spin-half and spin-one antiferromagnetic XXZ models and for the one-dimensional spin-half/spin-one ferrimagnetic XXZ model. The results for the ground-state properties of the isotropic points of these systems are seen to be in excellent quantitative agreement with exact results for the special case of the spin-half antiferromagnet and results of density matrix renormalization group (DMRG) calculations for the other systems. Extrapolated CCM results for the sublattice magnetization of the spin-half antiferromagnet closely follow the exact Bethe Ansatz solution, which contains an infinite-order phase transition at Δ=1. By contrast, extrapolated CCM results for the sublattice magnetization of the spin-one antiferromagnet using this same scheme are seen to go to zero at Δ≈1.2, which is in excellent agreement with the value for the onset of the Haldane phase for this model. Results for sublattice magnetizations of the ferrimagnet for both the spin-half and spin-one spins are non-zero and finite across a wide range of Δ, up to and including the Heisenberg point at Δ=1.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Dentistry
Subjects:	Q Science > QC Physics
Uncontrolled Keywords:	CCM; quantum magnets; phase transitions.
Publisher:	Springer
ISSN:	0022-4715
Last Modified:	04 Jan 2024 08:40
URI:	https://orca.cardiff.ac.uk/id/eprint/64282

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