Observation of the soft mode in the Sm-Cα*phase

We have performed the electro-optical measurements in an antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl 4(')-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC) and observed the soft mode in the chiral Sm-C(*)(alpha) phase. This is a direct consequence that the Sm-C(*)(alpha) phase is induced by the condensation of a tilting mode. A Landau-type theory was developed to analyze frequency dispersions in the second-order response and it was found that the Sm-A-Sm-C(*)(alpha) phase transition is close to a tricritical point.