Relative orientation of defects in smectic-C films*

In a 2D liquid crystal, each topological defect has a topological charge and a characteristic orientation, and hence can be regarded as an oriented particle. Theories predict that the trajectories of annihilating defects depend on their relative orientation [1,2]. Recently, these predictions have been tested in experiments on smectic-C films [3]. Those experiments find curved trajectories that are similar to the predictions, but the detailed relationship between the defect orientations and the far-field director field is different. To understand this difference, we improve the previous theories by adding the effects of elastic anisotropy and nonequilibrium dynamics. We find that the theory with elastic anisotropy gives good agreement with the experiment, and hence can describe the effects of defect orientation.
[1] A. J. Vromans and L. Giomi, Soft Matter 12, 6490 (2016).
[2] X. Tang and J. V. Selinger, Soft Matter 13, 5481 (2017).
[3] R. Stannarius, personal communication.