Title
Thermodynamic quantum critical behavior of the anisotropic Kondo necklace model
Date Issued
01 March 2009
Access level
open access
Resource Type
journal article
Author(s)
Centro Brasileiro de Pesquisas Físicas
Abstract
The Ising-like anisotropy parameter δ in the Kondo necklace model is analyzed using the bond-operator method at zero and finite temperatures for arbitrary d dimensions. A decoupling scheme on the double time Green's functions is used to find the dispersion relation for the excitations of the system. At zero temperature and in the paramagnetic side of the phase diagram, we determine the spin gap exponent ν z ≈ 0.5 in three dimensions and anisotropy between 0 ≤ δ ≤ 1, a result consistent with the dynamic exponent z = 1 for the Gaussian character of the bond-operator treatment. On the other hand, in the antiferromagnetic phase at low but finite temperatures, the line of Neel transitions is calculated for δ ≪ 1. For d > 2 it is only re-normalized by the anisotropy parameter and varies with the distance to the quantum critical point (QCP) | g | as, TN ∝ | g |ψ where the shift exponent ψ = 1 / (d - 1). Nevertheless, in two dimensions, a long-range magnetic order occurs only at T = 0 for any δ ≪ 1. In the paramagnetic phase, we also find a power law temperature dependence on the specific heat at the quantum critical trajectoryJ / t = (J / t)c, T → 0. It behaves as CV ∝ Td for δ ≤ 1 and ≈ 1, in concordance with the scaling theory for z = 1. © 2008 Elsevier B.V. All rights reserved.
Start page
348
End page
353
Volume
321
Issue
5
Language
English
OCDE Knowledge area
Física de partículas, Campos de la Física
Física de la materia condensada
Subjects
Scopus EID
2-s2.0-56449126390
Source
Journal of Magnetism and Magnetic Materials
ISSN of the container
03048853
Sponsor(s)
D. Reyes would like to thank professor Andre M.C. de Souza for useful computational help and professor A. Pérez-Gramatges for the careful reading of the manuscript. Han-Ting Wang would like to acknowledge the financial support from NKBRSF of China under Grant no. 2006CB921400. The authors D. Reyes and M.A. Continentino would like to thank also the Brazilian Agencies CNPq and FAPERJ for financial support.
Sources of information:
Directorio de Producción Científica
Scopus