Topological defects in cholesteric liquid crystal shells

TL;DR

This study explores the complex defect configurations in cholesteric liquid crystal shells, revealing new defect types stabilized by helical order and demonstrating topological transitions influenced by geometrical parameters.

Contribution

It provides the first detailed experimental and numerical analysis of defect structures unique to cholesteric shells, highlighting new defect types and topological transitions.

Findings

Identification of five distinct defect configurations in cholesteric shells.

Observation of defect transitions driven by geometrical parameters.

Discovery of non-geodesic defect recombination paths.

Abstract

We investigate experimentally and numerically the defect configurations emerging when a cholesteric liquid crystal is confined to a spherical shell. We uncover a rich scenario of defect configurations, some of them non-existent in nematic shells, where new types of defects are stabilized by the helical ordering of the liquid crystal. In contrast to nematic shells, here defects are not simple singular points or lines, but have a large structured core. Specifically, we observe five different types of cholesteric shells. We study the statistical distribution of the different types of shells as a function of the two relevant geometrical dimensionless parameters of the system. By playing with these parameters, we are able to induce transitions between different types of shells. These transitions involve interesting topological transformations in which the defects recombine to form new structures. Surprisingly, the defects do not approach each other by taking the shorter distance route (geodesic), but by following intricate paths.