Frequency-dependent dielectric contribution of flexoelectricity allowing control of state switching in helicoidal liquid crystals

摘要

The contribution of flexoelectric polarization to the dielectric susceptibility in helicoidal liquid crystals isnformulated for the static equilibrium case, and further in the case of a time-varying field. A dispersion of thendielectric permittivity due to the frequency response of flexoelectric switching is described. The special casenof a negative dielectric-anisotropy nematic material is considered and experimentally shown to agree with thenanalytical theory. It is further demonstrated how relaxation of the flexoelectric contribution to the dielectric tensornin this special case can be exploited to switch between states in cholesteric liquid crystal structures by alteringnthe applied time-dependent field amplitude, if u0002ε < 0 and (e1 − e3)2/(K1 + K3) > −u0002εε0. Consequentially, anversatile mechanism for driving between states in liquid crystal systems has been demonstrated and its implicationsnfor technology are suggested, and include dual-mode, bistable, and transflective displays.