SPIN-LIQUID PHASES IN 2-DIMENSIONAL FRUSTRATED XY MODELS

In this paper we consider the J(1)-J(2)-J(3) classical and quantum two -dimensional XY model. Spin-wave cal culations show that a spin-liquid phase still exists in the quantum case as for Heisenberg models. We f ormulate a semiclassical approach of these models based on spin-wave a ction and use a variational method to study the role played by vortice s. Liquid and crystal phases of vortex could emerge in this descriptio n. These phases seem to be directly correlated with the spin-liquid ph ase and to its crystalline interpretation. [S0163-1829(97)00838-2].