Coupling phenomenon of anti-connected hybrid alignment nematics in thin cell: From submicron to nanoscale

Abstract

Within Landau–de Gennes theory, we modeled a system consisting of two anti-connected hybrid alignment nematics (HAN). Our numerical simulation results indicated the occurrence of four states denoted as I, II, III and IV. The states undergo a structure transition as a function of the cell gap d. For d [Formula: see text] d0, where d0is the maximum value for the structure transition to occur, state I and II are bistable, whereas state III and IV are metastable and quadruply degenerate. We found that d0= 15[Formula: see text], where [Formula: see text] is the biaxial characteristic coherence length. When d[Formula: see text] [Formula: see text] d [Formula: see text] d0, where d[Formula: see text] = 7[Formula: see text] and d[Formula: see text] is the critical cell gap for order reconstruction (OR), continuous inversion walls appear both in state III and IV. We first found that the structure transition from inversion walls to defect walls occurs with decreasing d from the submicron to nanoscale. During this process, quadruply degenerate states in state III and IV transformed into doubly degenerate states. Meanwhile, states I and II remained bistable. When d = d[Formula: see text], all states reached a new type of OR pattern with two biaxial walls cross-linked with each other by a novel approach; i.e., from defect walls to OR.