Electrically Driven Instabilities in Smectic Liquid Crystal Films

Abstract

Various electric field driven instabilities in smectic liquid crystal films are discussed. Some of them resemble instabilities well-known from nematic liquid crystals. These are, for instance, the orientational Frederiks transition and electroconvection. However, the restriction of these two instabilities to two spatial dimensions can only be studied in free-standing smectic films, because free standing nematic liquid crystals are unstable. In addition several instabilities, being distinctive features of smectic liquid crystals are described. These are the undulational instability of the smectic layer structure and film buckling. All these different instability types are coupled in smectic C liquid crystals. For smectic C* liquid crystals films, the polarization Frederiks transition and the subharmonic regime of electroconvection are discussed. Electroconvection experiments with smectic C and C* films are reported that show the surface charge dominated ’vortex mode’ and convection of the Carr-Helfrich type, respectively.