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 exhibit giant dielectric constants whose value depends on the thickness of the measurement cell. Even though this must be the result of a spurious artifact, the intrinsic permittivity 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 accounting for polarization reorientation and the effect of insulating interfacial layers. We arrive at the conclusion that the perpendicular component of the permittivity $\varepsilon_{\perp}$ is of the order of $10$ in the prototypical ferroelectric nematogen DIO, while the parallel component $\varepsilon_{\parallel}$ is of the order of $150$. In this way, the dielectric tensor of DIO has been fully determined.