In homeotropically aligned nematics with negative dielectric anisotropy the electrohydrodynamic instability occurs above a bend Fréedericksz transition. In the presence of a magnetic field H→ parallel to the liquid crystal slab, ordered roll patterns with a welldefined uniform wave vector k→id appear above the onset of convection. By rotating the cell around an axis perpendicular to the slab by a small angle α, one can manipulate the system into a state with wave vector k→ = k→id + Δk→, where Δk→ is roughly perpendicular to k→id. We have studied experimentally the motion of defects, which then move essentially perpendicular to the rolls. The direction as well as the magnitude of the velocity as a function of Δk→ agrees with predictions of the weakly nonlinear theory. In particular, we obtain evidence for the nonanalyticity for Δk→ → 0.
ASJC Scopus subject areas
- Physics and Astronomy(all)