Mean-Field Theory of the Uniaxial Ferroelectric Smectic A Liquid Crystal Phase.

Following the groundbreaking discovery of the ferroelectric nematic liquid crystal phase (N_{F}), a series of closely-related new polar phases have also been found. An especially interesting one is the ferroelectric smectic A phase (SmA_{F}) with spontaneous polarization along the layer normal observed in a few materials of the N_{F} realm. Here, we present a mean-field molecular model that successfully captures the rich phase diagrams experimentally observed in the literature in terms of two parameters.

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

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.

Development of a high-frequency dielectric spectrometer using a portable vector network analyzer.

A simple and novel setup for high-frequency dielectric spectroscopy of materials has been developed using a portable vector network analyzer. The measurement principle is based on radio frequency reflectometry, and both its capabilities and limitations are discussed. The results obtained on a typical liquid crystal prove that the device can provide reliable spectra between 107 and 109 Hz, thus extending the capabilities of conventional impedance analyzers.

Collective and non-collective molecular dynamics in a ferroelectric nematic liquid crystal studied by broadband dielectric spectroscopy.

A great deal of effort has been recently devoted to the study of dielectric relaxation processes in ferroelectric nematic liquid crystals, yet their interpretation remains unclear. In this work, we present the results of broadband dielectric spectroscopy experiments of a prototypical ferroelectric nematogen in the frequency range 10 Hz-110 MHz at different electrode separations and under the application of DC bias fields. The results evidence a complex behavior in all phases due to the magnitude of polar correlations in these systems.

On the molecular origins of the ferroelectric splay nematic phase.

Nematic liquid crystals have been known for more than a century, but it was not until the 60s-70s that, with the development of room temperature nematics, they became widely used in applications. Polar nematic phases have been long-time predicted, but have only been experimentally realized recently. Synthesis of materials with nematic polar ordering at room temperature is certainly challenging and requires a deep understanding of its formation mechanisms, presently lacking.