The structure of disintegrating defect clusters in smectic C freely suspended films

TL;DR

This paper investigates how disclination clusters in smectic C films disintegrate into single defects, revealing geometrical patterns that follow predictable scaling laws and match theoretical models.

Contribution

It provides a detailed analysis of defect disintegration mechanisms and geometric arrangements in smectic C films, supported by experimental data and simple modeling.

Findings

Defect clusters disintegrate into single +1 defects in symmetric patterns.

Defect arrangements closely match superimposed singular solutions.

Defect patterns expand with a square-root time scaling law.

Abstract

Disclinations or disclination clusters in smectic C freely suspended films with topological charges larger than one are unstable. They disintegrate, preferably in a spatially symmetric fashion, into single defects with individual charges +1, which is the smallest positive topological charge allowed in polar vector fields. While the opposite process of defect annihilation is well-defined by the initial defect positions, a disintegration starts from a singular state and the following scenario including the emerging regular defect patterns must be selected by specific mechanisms. We analyze experimental data and compare them with a simple model where the defect clusters adiabatically pass quasi-equilibrium solutions in one-constant approximation. It is found that the defects arrange in geometrical patterns that correspond very closely to superimposed singular defect solutions, without additional director distortions. The patterns expand by affine transformations where all distances between individual defects scale with the same time-dependent scaling factor proportional to the square-root of time.