FIELD-DRIVEN 1ST-ORDER STRUCTURAL TRANSITION IN THE RESTRICTED GEOMETRY OF A SMECTIC-A CELL

An external field gives rise to a first-order transition in a smectic- A cell; the transition occurs by nucleation of focal conic domains. Th e physical mechanisms that govern the behavior of the new domain phase are different for small (rho much less than 1) and large (rho much gr eater than 1) values of the order parameters rho [rho=(domain radius)/ (cell thickness)]. The nucleation (rho much less than 1) is governed b y the elastic and field energies and is facilitated by bulk or surface irregularities, while the expansion (rho much greater than 1) is dete rmined by the balance of the field and anisotropic surface energy.