Some Peculiarities of Dielectric Spectroscopy in Ferroelectric Nematics

Abstract: Dielectric spectroscopy is known as one of the most powerful techniques for studying ferroelectric and other polar materials. Since the discovery of ferroelectricity in Liquid Crystals, it has been successfully employed for the characterization of ferro-, antiferro- and ferri-electric liquid crystalline phases. However, recently the Boulder group raised the question of the applicability of dielectric spectroscopy for characterizing ferroelectric nematics due to parasitic effects from the insulating alignment layers. This affects the apparent/measured values of the dielectric permittivity. In this paper, we study this effect in greater detail. The following issues will receive special attention: Are the real values of dielectric permittivity lower or higher than the measured ones? Can the real values of dielectric permittivity be recovered in the cell with alignment layers? We also provide an example of the effect of insulating alignment layers in a non-ferroelectric nematic phase.