Field-driven first-order structural transition in the restricted geometry of a smectic-Acell

An external field gives rise to a first-order transition in a smectic-A cell; the transition occurs by nucleation of focal conic domains. The physical mechanisms that govern the behavior of the new domain phase are different for small ({ρ}{}1) and large ({ρ}{}1) values of the order parameters {ρ} [{ρ}=(domain radius)/(cell thickness)]. The nucleation ({ρ}{}1) is governed by the elastic and field energies and is facilitated by bulk or surface irregularities, while the expansion ({ρ}{}1) is determined by the balance of the field and anisotropic surface energy.