STABILITY OF AN UMBILICAL DIRECTOR FIELD OF NEMATIC LIQUID-CRYSTAL IN A CLOSED CONICAL CAVITY

This letter studies the stability of a single umbilical director field of nematic liquid crystal (NLC) in a closed cavity with external electric field. To form the single umbilic structure, we filled NLC with negative dielectric anisotropy in a closed conical cavity and made molecules align perpendicular to the cavity wall. Electric field was applied along the symmetry axis of the cavity. Using the continuum theory, we show that an umbilical director field will transform to a director field of a hyperbolic singular point with disclination ring instead of a Poincare structure at a critical voltage.