Monte Carlo and spin dynamics study of the anisotropic Heisenberg model in two dimensions

By using Monte Carlo and molecular dynamics we study the static as well as the dynamical behavior of the classical two dimensional anisotropic Heisenberg model. Our results show that the vortices developed in such a model exhibit two different behaviors depending if the value of the anisotropy lambda lies below or above a critical value lambda(c). The in-plane and out-of-plane correlation functions were obtained numerically for lambda < lambda(c) and lambda > lambda(c). We found that the out-of-plane dynamical correlation function exhibits a central peak for lambda > lambda(c), but not for lambda > lambda(c), at temperatures above T-KT (C) 1997 American Institute of Physics.