# Reversal of Helicoidal Twist Handedness Near Point Defects of Confined Chiral Liquid Crystals

## TL;DR

This study reveals that in confined chiral liquid crystals, localized regions of opposite twist handedness can form near point defects, challenging the assumption of uniform handedness and impacting the stability of director configurations.

## Contribution

The paper demonstrates experimentally and numerically that localized opposite-handedness regions occur near point defects in confined chiral liquid crystals, introducing the new 'twistion' structure.

## Key findings

- Opposite-handedness regions arise near topological point defects.
- Twistions are newly identified localized structures with four point defects.
- Localized structures influence the stability of director configurations.

## Abstract

Handedness of the director twist in cholesteric liquid crystals is commonly assumed to be the same throughout the medium, determined solely by the chirality of constituent molecules or chiral additives, albeit distortions of the ground-state helicoidal configuration often arise due to the effects of confinement and external fields. We directly probe the twist directionality of liquid crystal director structures through experimental three-dimensional imaging and numerical minimization of the elastic free energy and show that spatially localized regions of handedness opposite to that of the chiral liquid crystal ground state can arise in the proximity of twisted-soliton-bound topological point defects. In chiral nematic liquid crystal confined to a film that has a thickness less than the cholesteric pitch and perpendicular surface boundary conditions, twisted solitonic structures embedded in a uniform unwound far-field background with chirality-matched handedness locally relieve confinement-imposed frustration and tend to be accompanied by point defects and smaller geometry-required energetically costly regions of opposite twist handedness. We also describe a new spatially localized structure, dubbed a "twistion", in which a twisted solitonic three-dimensional director configuration is accompanied by four point defects. We discuss how our findings may impinge on the stability of localized particle-like director field configurations in chiral and non-chiral liquid crystals.