Eur. Phys. J. B 84, 37-45 (2011)
https://doi.org/10.1140/epjb/e2011-20738-0

Regular Article

Green’s function approach to the low temperature properties of Cs₂CuCl₄: anisotropy effects

¹ Department of Physics, Razi University, Department of Physics, Bagh-e-Abrisham, 6714967346 Kermanshah, Iran
² Department of Physics, Sharif University of Technology, 11155-9161 Tehran, Iran

^a e-mail: rezania.hamed@gmail.com

Received: 6 September 2011
Published online: 31 October 2011

Abstract

We have studied the effect of both axial and transverse anisotropy on the critical field and thermodynamic properties of the field induced three dimensional antiferromagnetic Heisenberg model on the frustrated hexagonal lattice for Cs₂CuCl₄ compound. The spin model is mapped to a bosonic one with the hard core repulsion constraint and the Green’s function approach has been implemented to get the low energy spectrum and the corresponding thermodynamic properties. To find the critical field (B_c) we have looked for the Bose-Einstein condensation of quasi-particles (magnons) which takes place when the magnon spectrum vanishes at the ordering spiral wave vector. We have also obtained the dispersion of magnon spectrum in the critical magnetic field for each anisotropy parameter to find the spiral wave vector where the spectrum gets its minimum. The magnon energies show a linear dispersion relation close to the quantum critical point. The effect of hard core boson interaction on the single particle excitation energies leads to a temperature dependence of the magnon spectrum versus magnetic field. We have also studied the behavior of specific heat and static structure factor versus temperature and magnetic field.