Collective flow and defect dynamics of active nematic liquid crystals under an electric field*

Active nematic liquid crystals have attracted much attention as a model of mesoscale active turbulence in microtubule-kinesin suspensions and other biological systems. The chaotic flow is controlled by confinement and friction as has been demonstrated both experimentally and theoretically. An external electric field can be also used to manipulate the collective dynamics by inducing reorientation of the active elements. Here we numerically demonstrate the relatively unexplored effects of an electric field on the dynamics of two-dimensional active nematics [1]. We found transitions among three states, which are characterized by different degrees of flow anisotropy: the active turbulence, laning state, and uniformly aligned state. The average flow speed and its anisotropy are maximized in the laning state. We also found the localization of topological defects associated with the simultaneous creation and annihilation of two pairs of defects. It results in periodic oscillations between the active turbulence and laning state, which partly resemble the ones experimentally observed in a friction-controlled system. Our results provide insights into the way of controlling the flow patterns of active nematics with external fields.