Electric-Field Induced Nucleation and Growth of Focal Conic and Stripe Domains in Smectic A

Shila Garg, Kirstin Purdy, Erica Bramley (The College of Wooster)
I. I. Smalyukh, and O. D. Lavrentovich (Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University)

We study the electric field-induced first-order transition from a homeotropic smectic A structure into a polydomain texture that occurs through nucleation of toric focal conic domains (TFCDs). The process involves two steps: first nucleation of TFCDs of a size larger than a critical radius a*, and then a steady growth of TFCD to a secondary critical radius a** when surface anchoring effects become dominant and cause a transition from a circular TFCD to an elongated stripe domain (SD). Studies are performed for pure smectic A materials and for smectic A doped with kunipia nanoparticles. Non-destructive 3D imaging with the fluorescence confocal polarizing microscopy (FCPM) shows that the field-induced TFCDs can nucleate in the smectic A bulk. Clay particles reduce the energy barrier for nucleation as they distort the smectic A layers and thus increase the ground state energy. Simple elastic models of TFCD and SD allow us to describe the qualitative features of the observed phenomena.