Electrooptic Measurement in the Vicinity of SmA-SmCα* Phase Transition of an Antiferroelectric Liquid Crystal

Electrooptic measurements have been performed around the SmA-SmCα* phase transition point in an antiferroelectric liquid crystal 4-(1-methyl-heptyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC). The first-order electrooptic response was continuous with a small slope change at the SmA to SmCα* transition point in the temperature dependence curve, while the second-order electrooptic response exhibited an anomalous increase near the transition point. We present a simple theory and demonstrate that this anomaly originates in the pretransitional fluctuations. The frequency dispersion of the electrooptic response is also presented.