Soft Matter Physics research seminar: Pattern formation in confined nematic systems

Professor Apala Majumdar (University of Strathclyde, Glasgow) is giving a talk about his research into liquid crystals.

Nematic liquid crystals are classical examples of partially ordered materials intermediate between isotropic liquids and crystalline solids. We review the powerful Landau-de Gennes theory for nematic liquid crystals. Pierre-Gilles de Gennes was awarded the Nobel Prize in Physics in 1991, partly due to this powerful theory. We apply the Landau-de Gennes theory to prototype liquid crystal devices e.g. the Post Aligned Bistable Nematic Device designed by Hewlett Packard and the Planar Bistable Nematic Device.

We discuss the rich solution landscapes in both cases and highlight the role of defects in multistability and switching dynamics. We compute bifurcation diagrams for the solution landscapes as a function of the geometrical parameters that reveal interesting structural phase transitions. In particular, we report a novel Well Order Reconstruction Solution for the Planar Bistable Nematic Device and its intrinsic connections to interfacial phenomena for nematic liquid crystals. In the last part of the talk, we discuss novel ferronematic systems with nematic and magnetic order.

Our most striking numerical observations concern stable interior nematic point defects and magnetic domain walls, purely induced by geometric effects and the ferronematic coupling, without any external magnetic fields. These results have been obtained in collaboration with different research groups around the world and all collaborators will be acknowledged during the talk.