Focal conic domains in smectic thin films: Frustration-induced defects and their frustrated packings

Thursday, January 18, 2018 - 2:00pm - 2:50pm
Lind 305
Daniel Beller (Brown University)
In thermotropic smectic-A liquid crystals, the strong energetic preference for constant layer spacing often results in the spontaneous formation of focal conic domains (FCDs) to resolve large distortions. Collections of many FCDs self-organize into arrangements such as 2D lattices and polygonal textures, whose packing geometries involve beautiful geometric matching rules to ensure that smectic layers remain smooth. However, strong confinement can frustrate the typical FCD self-organization principles. I will discuss three such scenarios:

(1) The flower texture, where curved interfaces produce FCD packings with radially diverging hyperbolic focal curves.

(2) Colloidal particles in free-standing smectic films, decorated with a “corona” of FCDs, which play an important role in the elastocapillary assembly of the particles.

(3) A hybrid-aligned nematic cooled into the smectic-A phase, in which geometric memory from a pre-existing nematic boojum defect network directs the formation of incomplete FCDs into well-aligned rows, through an intermediate stripe instability.

For each of these scenarios, I will discuss geometrical models and their limitations, highlighting challenges that may require new numerical approaches.