Topological transition to rest in the electrohydrodynamics of nematics

Some nematic liquid crystals undergo electro-convective instabilities if forced by a low-frequency oscillating electric field. When the forcing amplitude is increased, a series of bifurcations occurs, which correspond to increasing disorder and reduction of the size of the electro-convective rolls. At a threshold, a transition to an electrohydrodynamic state characterised by a high density of topological defects occurs. Here, we show that in some nematic mixtures this transition is replaced by a topological transition to rest, that is, the electrohydrodynamics are quenched by the nucleation of a state that is topologically non-equivalent to the initial texture of the nematic.

部分向列相液晶（nematic liquid crystals）在低频交变电场驱动下会产生电对流不稳定性（electro-convective instabilities）。当驱动振幅增大时，体系会经历一系列分岔过程，对应无序度逐步提升且电对流辊的尺寸不断缩小。当达到某一阈值时，体系会跃迁至以高密度拓扑缺陷（topological defects）为特征的电流体动力学状态。本研究表明，在部分向列相混合体系中，该转变会被一种弛豫至静态的拓扑相变所取代，即电流体动力学行为会被一种与向列相初始织构拓扑不等价的物态的成核过程淬灭。