Light-induced surface sliding of the nematic director in liquid crystals

We report the effect of light-induced sliding of the nematic director over an isotropic boundary surface in an azo-dye doped liquid-crystal cell. We show that illumination of the cell with polarized laser light induces transient dynamic sliding followed by permanent reorientation of the director. The two effects are in competition and tend to orient the director along mutually orthogonal directions. The sliding can be controlled and even completely quenched by the amount of induced anchoring energy. A physical model is proposed which accounts for the experimental results. [S0031-9007(99)08539-7].