Field-driven helix unwinding in antiferroelectric liquid crystal cells

The interaction between the antiferroelectric helix and an electric field applied perpendicular to its axis is investigated, both experimentally and theoretically. A two-stage switching process is observed: (i) in the pretransitional regime the helix distorts and then unwinds to form a nonhelical antiferroelectric state, with the plane of the molecules parallel to the applied field; (ii) at higher fields switching to the ferroelectric state occurs. The mechanism for unwinding is the interaction of the applied field with a polarization that is induced by a change to the anticlinic ordering.