On the critical behaviour of two-dimensional XY helimagnets

Abstract

The authors study the nature of the excitation of a simple two-dimensional classical XY model with anisotropic coupling yielding a helical state at zero temperature. It is shown that, at low temperatures in the region of the Lifshitz point, the system displays two types of topological defect corresponding to vortices and to domain walls between regions of opposing chirality of the helical state. As a result of the existence of these excitations two phase transitions of XY and Ising character respectively are found.