Nematic topological defects positionally controlled by geometry and external fields.

Using a Landau-de Gennes approach, we study the impact of confinement topology, geometry and external fields on the spatial positioning of nematic topological defects (TDs). In quasi two-dimensional systems we demonstrate that a confinement-enforced total topological charge of > 1/2 decays into elementary TDs bearing a charge of = 1/2. These assemble close to the bounding substrate to enable essentially bulk-like uniform nematic ordering in the central part of a system.