Eur. Phys. J. B 46, 385-398 (2005)
https://doi.org/10.1140/epjb/e2005-00254-8

Thermodynamics of the quantum spin-S XXZ chain

¹ Departamento de Ciencias Exatas, Universidade Federal de Lavras, P.O. Box 37, CEP 37200-000, Lavras-MG, Brazil
² Departamento de Matemática e Computação, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Estrada Resende-Riachuelo s/no, Morada da Colina, CEP 27523-000, Resende-RJ, Brazil
³ Instituto de Física, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/nO, CEP 24210-340, Niterói - RJ, Brazil

Corresponding author: ^a or@stout.ufla.br

Received: 8 September 2004
Revised: 18 April 2005
Published online: 18 August 2005

Abstract

The thermodynamics of the spin-S anisotropic quantum XXZ chain with arbitrary value of S and unitary norm, in the high-temperature regime, is reported. The single-ion anisotropy term and the interaction with an external magnetic field in the z-direction are taken into account. We obtain, for arbitrary value of S, the β-expansion of the Helmholtz free energy of the model up to order and show that it actually depends on . Its classical limit is obtained by simply taking . At h=0 and D=0, our high temperature expansion of the classical model coincides with Joyce's exact solution [11]. We study, in the high temperature region, some thermodynamic quantities such as the specific heat and the magnetic susceptibility as functions of spin and verify for which values of S those thermodynamic functions behave classically. Their finite temperature behavior is inferred from interpolation of their high- and low-temperature behavior, and shown to be in good agreement with numerical results. The finite temperature behavior is shown for higher values of spin.