Field-induced reorientation of nematic liquid crystals with twofold degenerate alignment onSiOxsurfaces

Abstract

We show that an electric field normal to the boundaries confining a slab of nematic liquid crystals can induce a large change of the in-plane preferred orientation (i.e., the azimuthal angle). The degree of reorientation is controlled by the surfaces which have been coated with obliquely evaporated ${\mathrm{SiO}}_{x}.$ The experimental data are compared with simulations of a theoretical model where the effects of both large and small electric fields on the nematic orientation are considered. The reorientation phenomenon caused by the electric field appears to be a threshold phenomenon, due to the symmetry of the initial nematic orientation. For fields larger than the critical one, it is possible to define an effective surface energy for the system, containing the anisotropic surface energy and the contribution from the electric field.