Pairs of solitary domain walls in ferroelectric nematic

Polar ordering in confined samples of a ferroelectric nematic N_F often produces coexisting domains of opposite polarization. We report on the structure of the defect walls separating these domains in the material abbreviated DIO. In sandwich cells with parallel rubbing assembly, polarization is either antiparallel to the rubbing direction or parallel to it. Each polar domain is bound by two π-walls, with clockwise or counterclockwise rotation of polarization. The walls are of a finite width, representing static solitons. Two neighboring walls of the same sense of rotation form a 2π soliton of a winding number 1, while the 2π walls with opposite sense of rotation are topologically trivial. The pairs of a zero topological charge are removable by the electric fields that are much lower than the field required to remove the topologically stable 2π walls.