Magnetic field-induced Freedericksz transition in a chiral liquid crystal

Abstract

A wedge cell made of homeotropically treated glass plates is filled with a chirally doped nematic liquid crystal. When a sufficiently large magnetic field is applied in the cell plane, a bend-like distortion occurs above a Fréedericksz threshold field Hth. Hth is reduced from the achiral case because of a field-induced bend distortion that facilitates a chiral twist distortion. Measurements of Hth vs sample thickness are reported and compared favorably with a theoretical model presented herein. A further theoretical comparison is made between Hth and the electric-field-induced transition in a geometry, exhibiting a 2π azimuthal degeneracy. The results may have technological implications in, for example, in-plane switching devices.