Fluctuation-induced interactions in nematics with disordered anchoring energy

TL;DR

This paper studies how disordered surface anchoring energies affect fluctuation-induced interactions in nematic liquid crystals, revealing that disorder can significantly alter the interaction force, including changing its sign at certain separations.

Contribution

It introduces a theoretical analysis of pseudo-Casimir forces in nematics with disordered anchoring, showing disorder-induced renormalization effects on the interaction force.

Findings

Disorder renormalizes the effective surface anchoring parameter.

The interaction force can change sign due to disorder.

Disorder causes both quantitative and qualitative changes in the force.

Abstract

We examine fluctuation-induced (pseudo-Casimir) interactions in nematic liquid-crystalline films confined between two surfaces, where one of the surfaces imposes a strong homeotropic anchoring (ensuring a uniform mean director profile), while the other one is assumed to be a chemically disordered substrate exhibiting an annealed, random distribution of anchoring energies. We employ a saddle-point approximation to evaluate the free energy of interaction mediated between the two surfaces and investigate how the interaction force is influenced by the presence of disordered surface anchoring energy. It is shown that the disorder results in a renormalization of the effective surface anchoring parameter in a way that it leads to quantitative and qualitative changes (including a change of sign at intermediate inter-surface separations) in the pseudo-Casimir interaction force when compared with the interaction force in the absence of disorder.