Interplay of polar order and positional order in liquid crystals -- observation of re-entrant ferroelectric nematic phase

TL;DR

This paper reports the discovery of a re-entrant ferroelectric nematic phase in liquid crystals, where polar order disrupts the lamellar structure, revealing complex phase behavior driven by dipole interactions and Landau theory.

Contribution

It demonstrates the spontaneous destruction of lamellar structure by polar order and introduces a phase sequence involving ferroelectric nematic and smectic phases.

Findings

Ferroelectric nematic phase appears below a non-polar smectic phase.

Polar order can spontaneously destroy lamellar structures.

Landau theory explains the non-monotonic temperature dependence.

Abstract

We show that development of polar order may spontaneously destroy the lamellar structure of a liquid crystal. This results in an unusual sequence of phases with the ferroelectric nematic phase appearing below a non-polar smectic phase. The effect is related to unfavourable dipole interactions within the smectic layers and can be explained by Landau theory in which the temperature dependent term is non-monotonic as it is renormalized by spontaneous electric polarization.