Deformed states in paraelectric and ferroelectric nematic liquid crystals

TL;DR

This review explores how molecular shape, chirality, and confinement induce complex deformed states with parity breaking and splay-bend distortions in paraelectric and ferroelectric nematic liquid crystals.

Contribution

It provides a comprehensive overview of how various factors lead to deformed equilibrium and polydomain states in these liquid crystals, highlighting mechanisms like chirality and depolarization effects.

Findings

Chirality induces parity breaking in nematic states.

Splay cancellation reduces elastic and electrostatic energies.

Deformed states are influenced by molecular shape and confinement.

Abstract

Ground states of materials with orientational order ranging from solid ferromagnets and ferroelectrics to liquid crystals often contain spatially varying vector-like order parameter caused by inner factors such as the shape of building units or by the geometry of confinement. This review presents examples of how the shapes, chirality, and polarity of molecules and spatial confinement induce deformed equilibrium and polydomain states with parity breaking, splay, bend, and twist-bend deformations of the order parameter in paraelectric and ferroelectric nematic liquid crystals. Parity breaking results either from chirality of the constituent molecules, as a replacement of energetically costly splay and bend in paraelectric nematics, or in response to depolarization field in the ferroelectric nematic. Both paraelectric and ferroelectric nematics exhibit a splay cancellation effect, in which the elastic and electrostatic energies of splay along one direction are reduced by an additional splay along orthogonal directions.