Thermodynamic quantum critical behavior of the anisotropic Kondo necklace model

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:321

Article

Reyes, D.¹  Continentino, M. A.²  Wang, Han-Ting^3,4 

[1] Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil

[2] Univ Fed Fluminense, Inst Fis, BR-24210340 Niteroi, RJ, Brazil

[3] Chinese Acad Sci, Beijing Natl Lab Condensed Matter Phys, Beijing 100080, Peoples R China

[4] Chinese Acad Sci, Inst Phys, Beijing 100080, Peoples R China

关键词: Anisotropic Kondo necklace model;    Quantum phase transition;    Kondo insulator;   

DOI  :  10.1016/j.jmmm.2008.09.010

来源: Elsevier

【 摘 要 】

The Ising-like anisotropy parameter delta 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 vz approximate to 0: 5 in three dimensions and anisotropy between 0 <= delta <= 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 delta << 1. For d > 2 it is only re-normalized by the anisotropy parameter and varies with the distance to the quantum critical point (QCP) vertical bar g vertical bar as, T-N alpha vertical bar g vertical bar(Psi) where the shift exponent Psi = 1/(d-1). Nevertheless, in two dimensions, a long-range magnetic order occurs only at T = 0 for any delta << 1. In the paramagnetic phase, we also find a power law temperature dependence on the specific heat at the quantum critical trajectory J/t = (J/t)(c), T ! 0. It behaves as C-V alpha T-d for delta << 1 and approximate to 1, in concordance with the scaling theory for z = 1. (c) 2008 Elsevier B. V. All rights reserved.

【 授权许可】

Free