Landau Model of Electric Field Induced Smectic Phases in Thermotropic Liquid Crystals

(Received 22 April 1996, received in final form 24 June 1996, accepted 3 July 1996)

Abstract
We extend the Landau-de Gennes phenomenological model of the electric field induced isotropic-nematic phase transition to describe electric field induced smectic A phase transitions, for varying coupling between orientational and positional order parameters. Increasing the field, first order nematic-smectic A transition becomes second order at a tricritical point. The electric field induced non spontaneous nematic phase, can be metastable close enough to the isotropic-smectic A spontaneous transition temperature. For strong enough nematic-smectic coupling, when reentrant nematic is favored, a new non spontaneous smectic phase exists. An other new field induced paranematic-parasmetic phase transition is expected followed by a first order parasmectic-smectic A transition which disappears above a critical point.