Minimizers of the Landau-de Gennes energy around a spherical colloid particle

TL;DR

This paper analyzes energy-minimizing configurations of nematic liquid crystals around spherical colloids within the Landau-de Gennes framework, revealing different defect structures in small and large particle regimes.

Contribution

It provides a detailed analysis of the asymptotic behavior of minimizers in two regimes, introducing new defect configurations and linking Landau-de Gennes and Oseen-Frank models.

Findings

Small particles exhibit quadrupolar configurations with Saturn ring defects.

Large particles lead to axisymmetric dipole configurations with a single point defect.

The relationship between particle size and anchoring strength influences defect structures.

Abstract

We consider energy minimizing configurations of a nematic liquid crystal around a spherical colloid particle, in the context of the Landau-de Gennes model. The nematic is assumed to occupy the exterior of a ball of radius r_0, satisfy homeotropic weak anchoring at the surface of the colloid, and approach a uniform uniaxial state at infinity. We study the minimizers in two different limiting regimes: for balls which are small compared to the characteristic length scale r_0<<L, and for large balls, r_0>>L. The relationship between the radius and the anchoring strength W is also relevant. For small balls we obtain a limiting quadrupolar configuration, with a "Saturn ring" defect for relatively strong anchoring, corresponding to an exchange of eigenvalues of the Q-tensor. In the limit of very large balls we obtain an axisymmetric minimizer of the Oseen-Frank energy, and a dipole configuration with exactly one point defect is obtained.