Popova E. Nonlinear dynamic effects in ferroelectric liquid crystals

In this work, the results of electromechanical transformation investigations for various phases of ferroelectric liquid crystals (FLC) are presented. The separation of contributions to the electromechanical conversion due to the piezoelectric effect and two types of flexoelectric effects was achieved for the first time. In the course of studies of the relaxation process in some FLC phases, the existence of two regions where dispersions occur were detected in a smectic C phase. The low-frequency dispersion regions of and was shown to be caused by relaxation processes. These processes are, in turn, caused by small declinations of molecules at the near-electrode layer. The high-frequency dispersion is described by soft and Goldstoun modes. The results of studies of piezoelectric properties have shown these properties to be inherent for the smectic C* phase of ferroelectric liquid crystal irrespectivelly of the type of the paraelectric phase. It has been shown experimentally that the soft mode enhances the efficiency of electromechanical transformation in SmC* phase in the vicinity of SmA* SmC* phase transition. The possibility of existence of parametric effects in FLC was shown. The parametric amplification of mechanical oscillations in open resonant systems with FLC as an active medium has been obtained for the first time.