Escape into the third dimension in cholesteric liquid crystals

Abstract

Integer winding disclinations are unstable in a nematic and are removed by an ‘escape into the third dimension’, resulting in a non-singular texture. This process is frustrated in a cholesteric material due to the requirement of maintaining a uniform handedness and instead results in the formation of strings of point defects, as well as complex three-dimensional solitons such as heliknotons that consist of linked dislocations. We give a complete description of this frustration using methods of contact topology. Furthermore, we describe how this frustration can be exploited to stabilise regions of the material where the handedness differs from the preferred handedness. These ‘twist solitons’ are stable in numerical simulation and are a new form of topological defect in cholesteric materials that have not previously been studied.