Electric-field-induced layer reorientation in ferroelectric liquid crystals

We show that a sufficiently large ac electric field reorients the smectic layers irreversibly in chiral smectic-C liquid crystals. Using uniformly aligned samples, prepared by unidirectional buffing, it is demonstrated that at a given temperature the layers tilt away from the buffing axis, b^, by an angle equal to the molecular tilt angle of the smectic-C phase. In this new configuration the molecules lie along b^ and the layers are tilted. It is also found that a small dc bias field can control the direction of the tilted layers with respect to b^. Furthermore, microscopic observations suggest that the chevron layers, common in the ferroelectric smectic-C phase, are absent after the electic field treatment which eliminates zig-zag-type defects.