Electric-Field-Induced Apparent Tilt Angle and Devil's Staircase in SmC_α ^* of an Antiferroelectric Chiral Smectic Liquid Crystal

Abstract

The SmC α * phase which was discovered between SmA and SmC * in 4-(1-metylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC) has been studied by means of electric-field-induced tilt angle measurements and conoscopic observation. The induced tilt angle increases not smoothly but stepwise in SmC α * and its neighboring SmA temperature ranges, suggesting successive structural changes, namely, Devil's staircase. According to the conoscopic figures, the existence of the ferrielectric orientation was confirmed. Devil's staircase observed as a result of changing field strength was discussed in comparison with that induced by changing temperature.