Twisted domains in ferroelectric nematic liquid crystals

Ferroelectric nematics present properties promising for applications, which strongly depend on the confinement conditions and the presence of defects. In this work, we have observed and analysed textures in the cells with homogeneous geometry for a ferroelectric nematogen. The studied compound reveals the ferroelectric nematic phase, NF, directly on cooling from the isotropic phase. The NF phase is stable and persists down to the room temperatures. Textures in the homogeneous cell with antiparallel alignment prefer to be arranged in twisted domains with borderlines oriented preferentially in the perpendicular direction with respect to the surface alignment (rubbing direction). We have described these domains and developed a model of 2/pi disclinations, which are separating the areas with an opposite twist sense. We discussed the character of disclination charge and explained why these disclination lines prefer to be oriented perpendicularly to the rubbing direction.