Dielectric Response of Chiral Smectic Liquid Crystals

A discrete phenomenological model is used to study theoretically the dielectric response of chiral smectic liquid crystals in external harmonic electric field. In this model, the tilt order parameter describes the magnitude and direction of the director tilt from the smectic layer normal. Interactions between layers can be of different nature: steric, van der Waals, quadrupolar and electrostatic dipolar; and competing interactions between nearest and next nearest layers are taken into account. The strength of these interactions can change with temperature. We consider the effect of quadrupolar interactions on dielectric loss of the chiral smectic liquid crystal phases. From the free energy function, we obtain an analytical expression for the dielectric loss in terms of eigen-frequencies of the amplitude and phase modes. The frequency dependence of dielectric loss is presented.