A Monte Carlo study of crossover behaviour and solitons in an anisotropic Heisenberg chain

The authors have examined the spin correlations and configurations of a classical Heisenberg antiferromagnetic chain with weak easy-plane anisotropy by means of a Monte Carlo simulation. The results show the expected crossover from XY to Heisenberg behaviour as the temperature is raised. Direct examination of the spin configurations shows the presence of out-of-easy-plane solitons as predicted by Mikeska (1980). However this soliton picture …