Helix Unwinding Process in a Short-Pitch Ferroelectric Liquid Crystal Mixture Studied by Conoscopy

Abstract

The helix unwinding process in a short-pitch chiral smectic C (SmC*) mixture has been studied by means of conoscope observation and its simulation based on the elastic theory and 4×4 matrix method. Upon the application of an electric field parallel to the smectic layer, an isogyre shifts perpendicular to the field keeping a uniaxial figure (low field), splits along the direction parallel to the field (intermediate field), and then changes its splitting direction to that perpendicular to the field. This indicates that the biaxiality of the system changes its sign during the field application. This behavior is essentially the same as that expected on the basis of the simulation obtained by applying the 4×4 matrix method to deformed helices under an electric field. It is also noted that the biaxial figure under the intermediate field is similar to that observed in the ferrielectric SmCγ* (SmCferri1) phase, although it should not be.