Theoretical model for layer rotations in smectic-A* liquid crystals subject to asymmetric electric fields

Recently, observations of the rotation of smectic layers under certain expe rimental conditions have been reported in the literature. In this work, the mechanism of such rotations in chiral smectic-A* liquid crystals under the action of asymmetric, periodic electric fields is studied theoretically. T he general conditions for layer rotations have been established using symme try arguments, and a generalized dynamical theory of the chiral smectic-A* phase, coupling layer rotations and the electroclinic effect, has been deve loped. The theory is applied in the specific case when an asymmetric sawtoo th electric field is applied over the system, and the dependence of the ave rage angular velocity of the smectic layers on the relevant material consta nts of the liquid crystal and experimental control parameters is calculated . By rewriting the final equations into dimensionless form, it is demonstra ted that the system exhibits a universal behavior, reducing the number of i ndependent material constants and control parameters considerably. [S1063-6 51X(99)09211-9].