Susser Adam L, Kralj Samo, Rosenblatt Charles
Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, Slovenia and Jožef Stefan Institute, Koroška cesta 160, SI-2000 Maribor, P.O. Box 3000, SI-1000 Ljubljana, Slovenia.
Soft Matter. 2021 Nov 3;17(42):9616-9623. doi: 10.1039/d1sm01124c.
A patterned surface defect of strength = +1 and its associated disclination lines can decompose into a pair of surface defects and disclination lines of strength = +1/2. For a negative dielectric anisotropy liquid crystal subjected to an applied ac electric field , these half-integer defects are observed to wobble azimuthally for > than some threshold field and, for sufficiently large fields, to co-revolve antipodally around a central point approximately midway between the two defects. This behavior is elucidated experimentally as a function of applied field strength and frequency , where the threshold field for full co-revolution scales as . Concurrently, nematic electrohydrodynamic instabilities were investigated. A complete field frequency "phase diagram" compellingly suggests that the induced fluctuations and eventual co-revolutions of the ordinarily static defects are coupled strongly to-and driven by-the presence of the hydrodynamic instability. The observed behaviour suggests a Lehmann-like mechanism that drives the co-revolution.
强度为(+1)的图案化表面缺陷及其相关的位错线可以分解为一对强度为(+1/2)的表面缺陷和位错线。对于受到外加交流电场(\vec{E})作用的负介电各向异性液晶，当电场(\vec{E})大于某个阈值场时，这些半整数缺陷会沿方位角摆动，并且在足够大的场强下，会围绕位于两个缺陷之间大致中点的中心点进行反位相共旋转。实验表明，这种行为是外加场强(\vec{E})和频率(\omega)的函数，其中完全共旋转的阈值场与(\omega)成比例。同时，研究了向列型电流体动力学不稳定性。一个完整的场强(\vec{E}) - 频率(\omega)“相图”有力地表明，通常静态缺陷的诱导波动和最终共旋转与流体动力学不稳定性的存在密切相关，并由其驱动。观察到的行为表明存在一种类似雷曼的机制来驱动共旋转。
