Grid pattern emerging from complex dynamics of defects

The formation process and growth dynamics of the grid pattern, a cellular convective pattern in the electroconvection of nematic liquid crystals, are investigated. The grid pattern appears via a disordered state called defect turbulence with the increasing of an applied voltage. The averaged defect density increases with the applied voltage and then the defects that have been in the continuous process of creation and annihilation are frozen as grid cells forming domain structures. The area fraction of the grid domains is adopted as the order parameter. The temporal growth of the area fraction for the step voltage was also measured. By applying the Kolmogorov-Avrami model to the results, it is suggested that the growth dynamics of the grid domain is not primarily governed by domain growth, but by the local transition of the rolls to the cellular flow via preliminary grid structures that transiently appear.