KINETICS OF PHASE ORDERING IN THE 2-DIMENSIONAL COUPLED XY-ISING MODEL

The ordering kinetics of a coupled XY-Ising model on a two-dimensional square lattice quenched from a disordered state to a low-temperature ordered phase is investigated via Monte Carlo dynamical simulations. T he decay process of the two types of topological defects (point vortic es and line defects of Ising domain walls) and the interaction between them controls the long-time dynamics of the ordering. In particular, the decoupling of XY degrees of freedom across Ising domain walls lead s to the pinning of vortices near the walls, which considerably slows down the growth of XY order: it shows a power-law growth in time with the exponent phi(XY)similar or equal to 0.38. This vortex pinning also appears to give rise to a stretched exponential relaxation in the XY autocorrelation function. The dynamic scaling for both XY and Ising or der parameters in the presence of multiple length scales is discussed.