Theory of field-induced quantum phase transition in spin dimer system Ba$_3$Cr$_2$O$_8$

O. I. Utesov; A. V. Syromyatnikov

doi:10.1016/j.jmmm.2014.01.045

paper

Theory of field-induced quantum phase transition in spin dimer system Ba $_{3}$ Cr $_{2}$ O $_{8}$

arXiv:1405.0564 · doi:10.1016/j.jmmm.2014.01.045

Abstract

Motivated by recent experiments on Ba $_{3}$ Cr $_{2}$ O $_{8}$ , we propose a theory describing low-temperature properties in magnetic field $h$ of dimer spin- $\frac{1}{2}$ systems on a stacked triangular lattice with spatially anisotropic exchange interactions. Considering the interdimer interaction as a perturbation we derive in the second order the elementary excitations (triplon) spectrum and the effective interaction between triplons at the quantum critical point $h = h_{c}$ separating the paramagnetic phase ( $h < h_{c}$ ) and a magnetically ordered one ( $h_{c} < h < h_{s}$ , where $h_{s}$ is the saturation field). Expressions are derived for $h_{c} (T)$ and the staggered magnetization $M_{⊥} (h)$ at $h$ close to $h_{c}$ . We apply the theory to Ba $_{3}$ Cr $_{2}$ O $_{8}$ and determine exchange constants of the model by fitting the triplon spectrum obtained experimentally. It is demonstrated that in accordance with experimental data the system follows the 3D BEC scenario at $T < 1$ K only due to a pronounced anisotropy of the spectrum near its minimum. Our expressions for $h_{s}$ , $h_{c} (T)$ and $M_{⊥} (h)$ fit well available experimental data.

arXiv comment9 pages, 6 figures

Theory of field-induced quantum phase transition in spin dimer system Ba $_{3}$ Cr $_{2}$ O $_{8}$

Abstract

References in corpus (8)

Cited by in corpus (2)

Theory of field-induced quantum phase transition in spin dimer system Ba3​Cr2​O8​

Abstract

References in corpus (8)

Cited by in corpus (2)

Theory of field-induced quantum phase transition in spin dimer system Ba $_{3}$ Cr $_{2}$ O $_{8}$