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
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.
PACS: 05.30.Ch – Quantum ensemble theory / 75.10.Jm – Quantized spin models / 75.10.Hk – Classical spin models
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005