Flexoelectric response at defect sites in nematic inversion walls

Electric field experiments have been carried out on +1 and -1 defects formed in alignment inversion walls, in a planarly aligned nematic phenyl benzoate. The results show that the defects are non-singular in the core and exhibit a flexoelectric response to an applied d.c. or low frequency a.c. field. When the c-director flux lines are circular, as in a +1 defect in a wall parallel to the easy axis, flexoelectro-optic switching characterized by an azimuthal angle variation is observed. When the c-director flux is radial, the response is seemingly through polar angle variations involving no rotation of the extinction brushes due to crossed polarizers. This conclusion follows from the field-induced structural distortions observed at a -1 defect having a combination of radial and tangential c-director fields.