arXiv:cond-mat/0104288 · Physical review. B, Condensed matter
Relaxational dynamics study of the classical Heisenberg spin XY model in spherical coordinate representation
Beom Jun Kim, Petter Minnhagen, Suhk Kun Oh, Jean Soo Chung
Abstract
The two- and three-dimensional classical Heisenberg spin $\mathrm{XY}$ $(\mathrm{CHS}XY)$ models, with the spherical coordinates of spins taken as dynamic variables, are numerically investigated. We allow the polar \ensuremath{\theta} and azimuthal $\ensuremath{\varphi}$ angles to have uniform values in $[0,\ensuremath{\pi})$ and $[\ensuremath{-}\ensuremath{\pi},\ensuremath{\pi}),$ respectively, and the static universality class is shown to be identical to the classical $\mathrm{XY}$ model with two-component spins, as well as the $\mathrm{CHS}\mathrm{XY}$ model with a different choice of dynamic variables, conventionally used in the literature. The relaxational dynamic simulation reveals that the dynamic critical exponent z is found to have the value $z\ensuremath{\approx}2.0$ for both two and three dimensions, in contrast to $z\ensuremath{\approx}d/2$ $(d=$ spatial dimension) found previously with spin dynamics simulation of the conventional $\mathrm{CHS}\mathrm{XY}$ model. Comparisons with the usual two-component classical $\mathrm{XY}$ model are also made.