Zig-Zag Defects and Disclinations in the Surface-Stabilized Ferroelectric Liquid Crystals

Characteristic features of zig-zag defects and disclinations in surface-stabilized ferroelectric liquid crystal cells are presented. It is pointed out that there exist two kinds of zig-zag defects, i.e. , a lightning type and a hairpin type, which appear alternatively along the smectic layer normal. This fact indicates that two types of mismatching of a layer bend structure cause two kinds of zig-zag defects. Switching between two twisted states occurs with the formation of internal boat-shaped disclination loops in relation to the zig-zag defects. The nucleation process of the boat-shaped domains is quite characteristic; the bows appear on each side of the bright hairpin-type lines, while the sterns appear on both sides of the dark lightning-type lines. A model structure is proposed in order to interpret the experimental observation around the zig-zag defect lines on the basis of disclination dynamics.