Constraining the value of the dielectric constant of the ferroelectric nematic phase

Abstract

Ferroelectric nematic liquid crystals are currently being subject to a plethora of investigations since they are of great fundamental interest and could potentially foster promising applications. However, many basic aspects are still poorly understood, among which the problem of the dielectric constant stands out. Ferroelectric nematics have previously been reported to exhibit giant dielectric constants whose value depends on the thickness of the measurement cell, claims that have recently been shown to be the result of an incorrect interpretation of the experimental data. The intrinsic permittivity of these materials has not been determined yet. In this work, we tackle this problem by modeling the dielectric response of the liquid crystal filled cell through an equivalent circuit proposed by Clark et al. [Phys. Rev. Res. 6, 013195 (2024)] accounting for polarization reorientation and the effect of insulating interfacial layers. We arrive at the conclusion that the perpendicular component of the permittivity ε⊥ is of the order of 10 in the prototypical ferroelectric nematogen DIO, while the parallel component ε is of the order of 150. In this way, the dielectric tensor of DIO has been fully determined.