Electric Fields Normal to the Helix Axis

For a chiral nematic with positive dielectric anisotropy and an electric field E orthogonal to the helix axis (z), then we observe a chiral nematic to unwound nematic transition for d p. The analysis [132,139] of the unwinding mechanism is exactly the same as for the magnetic field case with the coupling -YiAxin H) replaced by - AnAe n E) in the free energy density expression. The equilibrium condition (see Eq. 127) or Euler s equation then becomes 

Eollowing the same solution route as for the magnetic field case leads to a coherence length 2 given by 

As discussed in Sec. 2.4.2, this helix unwinding corresponds to a decrease in the 

Flexoelectricity arises in liquid crystals due to their shape asymmetry, i.e., pear , teardrop , banana , etc., associated with a strong permanent dipole moment. Macro- 

In the geometry to be considered, the chiral nematic is contained between cell walls in the x, y plane with the uniform surface alignment layers designed to align the helix axis along x with the electric field applied along z (see Fig. 35). In such a sandwich like cell [29, 173-175], the director spirals along the x direction in the z, y plane and is therefore described by 

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