Order Electricity and Surface Orientation in Nematic Liquid Crystals

Abstract

A nematic liquid crystal should present an order electric polarization associated with the gradient of order parameter, in addition to the flexoelectric polarization associated with the gradient of orientation. Using thermodynamical arguments, we show that the order-electricity coefficients are of the same order as the flexoelectric ones. The dielectric energy resulting from the order polarization can explain the unsolved problem of the spontaneous titled orientation at the nematic-isotropic (or air) interfaces. The core of disclination lines can also present electric multipoles.