Direction of flexoelectric polarization in smectic *CG phases of chiral smectic liquid crystals

Abstract

Polarization in antiferroelectric liquid crystals has two origins: The piezoelectric polarization which is of chiral origin and the flexoelectric polarization which originates in different orientation of tilts in neighboring layers. The flexoelectric polarization is perpendicular to the tilt direction only if the structure is uniformly helicoidally modulated. In structures like and the flexoelectric contribution might be significant and it can be non-parallel to the piezoelectric component. Hence it may deviates the direction of polarization from the perpendicular direction significantly. The angle formed by the polarization and the tilt is therefore general and as such the basic characteristic of the Sm phase can be recognized. It seems that this aspect was completely overlooked in the past. In this contribution we analyze the dependence of the polarization direction on the phase structures and on the values of piezoelectric and flexoelectric coefficients in the discrete phenomenological model.