An ANNNXY model for transversely polarised non-chiral smectic liquid crystals

Abstract

We propose an axial next nearest neighbour xy (ANNNXY) model to describe phase transitions in smectic liquid crystals made of bent non-chiral molecules which exhibit transverse polarisation. The model includes a polar and a quadrupolar NN coupling as well as a competing antiferroelectric NNN coupling between the layers. As the temperature is lowered, the most general sequence of phases predicted by the model is: paraelectric-helielectric ()- antiferroelectric-reentrant -4 layer antiphase-helielectric ()-ferroelectric. We believe that and the antiphase have been seen in very recent experiments.