Three-dimensional soliton-like distortions in flexoelectric nematic liquid crystals: modeling and linear analysis

TL;DR

This paper models and analyzes three-dimensional soliton-like distortions in flexoelectric nematic liquid crystals, revealing their stability, characteristics, and potential for nanotransport applications, with predictions aligning well with experimental observations.

Contribution

It introduces a variational model for 3D soliton-like waves in flexoelectric nematic liquid crystals and performs stability analysis, a novel approach in this context.

Findings

Model predictions match experimental data.

Identifies flexoelectricity as key to soliton formation.

Provides stability thresholds and wave characteristics.

Abstract

This article models experimentally observed three dimensional particle-like waves that develop in nematic liquid crystals, with negative dielectric and conductive anisotropy, when subject to an applied alternating electric field. The liquid crystal is confined in a thin region between two plates, perpendicular to the applied field. The horizontal, uniformly aligned director field is at equilibrium due to the negative anisotropy of the media. However, such a state is unstable to perturbations that manifest themselves as confined, bullet-like, director distortions traveling up and down the sample at a speed of several hundred microns per second. It is experimentally predicted that flexoelectricity plays a key role in generating the soliton-like behavior. We develop a variational model that accounts for ansiostropic dielectric, conductive, flexolectric, elastic and viscous forces. We perform a stability analysis of the uniformly aligned equilibrium state to determine the threshold wave numbers, size, phase-shift and speed of the soliton-like disturbance. We show that the model predictions are in very good agreement with the experimentally measured values. The work models and analyzes a three-dimensional soliton-like instability reported, for the first time in flexoelectric liquid crystals, pointing towards a potential application as a new type of nanotransport device.