Nikkhou M, Škarabot M, Muševič I
J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia.
Phys Rev E. 2016 Jun;93(6):062703. doi: 10.1103/PhysRevE.93.062703. Epub 2016 Jun 13.
We use the laser tweezers to create isolated pairs of topological point defects in a form of radial and hyperbolic hedgehogs, located close and attracted to a thin fiber with perpendicular surface orientation of nematic liquid crystal molecules in a thin planar nematic cell. We study the time evolution of the interaction between the two monopoles by monitoring their movement and reconstructing their trajectories and velocities. We find that there is a crossover in the pair interaction force between the radial and hyperbolic hedgehog. At small separation d, the elastic force between the opposite monopoles results in an increase of the attractive force with respect to the far field, and their relative velocity v scales as a v(d)∝d^{-2±0.2} power law. At large separations, the two oppositely charged monopoles can either attract or repel with constant interaction force. We explain this strange far-field behavior by the experimental inaccuracy in setting the fiber exactly perpendicular to the cell director.
我们使用激光镊子在薄平面向列相液晶盒中创建呈径向和双曲刺猬形式的孤立拓扑点缺陷对，这些缺陷靠近并被具有垂直表面取向的向列相液晶分子的细纤维吸引。我们通过监测两个单极子的运动并重建它们的轨迹和速度来研究它们之间相互作用的时间演化。我们发现径向刺猬和双曲刺猬之间的对相互作用力存在交叉。在小间距d时，相反单极子之间的弹力导致相对于远场吸引力增加，并且它们的相对速度v按v(d)∝d^{-2±0.2}幂律缩放。在大间距时，两个带相反电荷的单极子可以以恒定相互作用力吸引或排斥。我们通过将纤维精确设置为垂直于单元指向矢时的实验误差来解释这种奇怪的远场行为。
