title: Landau-de Gennes theory of surface-enhanced ordering in smectic films.
abstract: A Landau theory for surface-enhanced ordering in smectic-A free-standing films is described, based on a generalization of de Gennes' model for a "presmectic" fluid confined between two walls. According to the theory, smectic ordering in free-standing films heated above the bulk smectic melting temperature is due to an intrinsic surface contribution rather than an external field. The theory yields a persistent finite-size effect, in that the film melting temperatures do not tend to the bulk transition temperature in the limit of infinite film thickness. It also predicts that a continuous transition from (N+1)- to N-layer films is impossible without an external field. The theory closely fits existing experimental data on layer-thinning transitions in compounds which exhibit a bulk smectic-A to nematic phase transition. Possible origins of the intrinsic surface contribution are discussed.
authors: Department of Physics and Guelph-Waterloo Physics Institute, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors: A N
authors: AN
authors: Shalaginov
authors: D E
authors: DE
authors: Sullivan