Textures and Interactions between Vortices in the 2D XY Field of Freely Suspended SmC and SmC* Liquid Crystal Films
Apichart Pattanaporkratana, ,
University of Colorado at Boulder
In a few-layer thick freely suspended tilted smectic (SmC) liquid crystal film, the local azimuthal orientation of the molecular tilt is a two-dimensional XY field. An island on the film (a circular region of greater thickness), presents a strong azimuthal boundary condition at its edge that forces a strength +1 chiral vortex into XY field (inside an island). Each such vortex is paired with a strength -1 vortex in the field (on the background film), forming a chiral topological dipole. Chiral dipoles with the same handedness form polar chains with the dipoles pointing in the same direction and along the chain, whereas dipoles of opposite handedness form quadrupolar structures. We use optical tweezers to manipulate islands on freely suspended films to study inter-island forces and structures of such quadrupoles and dipolar chains. Effects of spontaneous polarization induced by chiral smectic C (SmC*) phase on the interactions of islands and structures of vortices on freely suspended SmC* films are discussed.