The origin of memory in nematics with quenched disorder

Memory effects and glassy behavior have been repeatedly observed in disordered nematic liquid crystals. Here we present turbidity experiments and computer simulations aimed at studying key features such as dynamics, history dependence and system topology in randomly perturbed nematics. Electric field-cooling alignment has been employed to prepare samples in suitably oriented starting states. Remarkable remnant order and slow dynamics are found both by experiment and simulations, indicating that random disorder can, by itself, induce a nematic glass state even without perturber restructuring. We show that the topology of the simulated nematic ordering in the presence of static random disorder can be described as an ensemble of pinned defect lines and that the memory of the system is a consequence of the pinning of these strings