Competing Polarization Effects in a Homeotropically Aligned Smectic Liquid Crystal

Abstract

We examine the equilibrium configurations of a thin SmA* liquid crystal film with its layers parallel to a lower substrate and a free upper surface. The molecules can exhibit variations in molecular tilt or twist around the smectic cone which are influenced by an in-plane electric field. We examine the competing effects of flexoelectricity and spontaneous polarization on the molecular tilt and twist. Our analysis is based upon a continuum theory for smectics which allows variation in the smectic layer spacing and the molecular tilt. For a fixed voltage the system can exhibit qualitatively different types of equilibrium profiles, depending on the relative sizes of the spontaneous polarization and flexoelectric contributions to the bulk energy. Energy and stability calculations allow us to predict physically relevant molecular configurations. These structures are closely related to synclinic and anticlinic arrangements in liquid crystal freestanding films.

Keywords:

• SmA* liquid crystals
• continuum theory
• equilibrium configurations
• polarization
• flexoelectricity