Study of the SmCα* Phase in the Tokyo Mixture by Conoscopy Using Tilted Cell

Abstract

We observed the existence of the SmCα* phase in the so-called Tokyo mixture, which has been used for studying V-shape switching by a number of research groups. Conoscopic observations, birefringence measurements using a set-up that employs a photo elastic modulator (PEM) and dielectric measurement were used for studying the behavior of the SmCα* phase. In particular, a conoscopic method using tilted cells was used to observe the conoscopy of the large tilt angle phase. We found that the tilted conoscopic method is very useful for analyzing large tilt smectic phases. The SmCα* phase was observed in a narrow temperature range from 63.0°C to 63.4°C. This is the first report of an observation of this phase in the Tokyo Mixture. It showed uniaxiality at low voltage but changed to biaxiality parallel to the electric field at high voltage in the conoscopic experiment. The absolute value of the biaxiality was quite high, up to 0.003, which means that the unwinding process of SmCα* is different from that of SmC*. This high parallel biaxiality implies the emergence of ferri-like structure, that is, co-existence of synclinic order and anticlinic order, during the field induced unwinding process.