Surface effects in field-induced smectic transitions

We study the surface behavior of a semi-infinite smectogenic sample bounded by a solid wall, in the presence of an external electric field. Our analysis is performed in the framework of a Landau-de Gennes theory. For the sake of simplicity, we consider only the case in which, in the absence of field and surfaces, a direct isotropic to smectic-A transition occurs, while in the presence of the electric field a nonspontaneous nematic phase appears. Two new surface phases are identified, namely a parasmectic and a surface-induced smectic phase. The shifts in the transition temperatures and the critical behavior of the surface states are analyzed.