Double-peak polarization current response in the unusual SmA ^* phase of a fluorinated high-tilt antiferroelectric liquid crystal

A detailed investigation of the dielectric, electro-optical properties and X-ray studies have been made in the vicinity of the transition from Smectic-A^* to Smectic-C^* as well as in the Smectic-A^* phase of a newly synthesized partially fluorinated high-tilt antiferroelectric liquid crystal (AFLC) material. The Smectic-A ^* phase of this material exhibits high optical tilt, minimum layer shrinkage from paraelectric-to-ferroelectric phase transition and unusual dielectric behavior, which are the complementary evidences that the Smectic-A^* phase is of de Vries type. Double-peak polarization current response and tristable-optical-switching studies have revealed an antiferroelectric molecular ordering in the de Vries SmA^* phase of this material. Two distinct dielectric relaxation peaks in the SmA ^* phase also complement the antiferroelectric-like ordering of the molecule in the SmA^* phase. The material undergoes a first-order SmA^*-SmC^* transition which is confirmed by a high enthalpy change and the discontinuity of the dielectric parameters at the phase transition.