FERROELECTRIC LIQUID-CRYSTALS - FROM THE PLANE-WAVE TO THE MULTISOLITON LIMIT

In the presence of external fields or in restricted geometries, the originally continuous helical symmetry of the Sm C* phase is broken by the appearence of field- or geometry-induced soliton-like domain walls. As a result of this symmetry breaking, a crossover between the plane-wave-like and soliton-like regime occurs in both static and dynamic properties which is responsible for some remarkable phenomena such as field-induced optical biaxiality or a field-induced band structure of collective excitations. Whereas we find in the plane-wave-like regime a degenerate soft mode which splits below the Sm A-->Sm C* transition into a symmetry recovering Goldstone-phason-mode and an amplitudon mode, we find in the soliton regime a splitting of the phason mode into acoustic and optic-like branches separated by a band gap. Within the same framework we also discuss other remarkable and extraordinary properties such as reentrant phases, Lifshitz points, one dimensional photonic band gaps and thickness dependent phase diagrams.