Co-revolving topological defects in a nematic liquid crystal.
basic_science · Level V
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- Record sourced from PubMed, PMID 34622261.
- Also identified by DOI 10.1039/d1sm01124c and PMC identifier 8573773.
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Abstract
A patterned surface defect of strength <i>m</i> = +1 and its associated disclination lines can decompose into a pair of surface defects and disclination lines of strength <i>m</i> = +1/2. For a negative dielectric anisotropy liquid crystal subjected to an applied ac electric field <i>E</i>, these half-integer defects are observed to wobble azimuthally for <i>E</i> > 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 <i>E</i> and frequency <i>ν</i>, where the threshold field for full co-revolution scales as <i>ν</i><sup>1/2</sup>. Concurrently, nematic electrohydrodynamic instabilities were investigated. A complete field <i>vs.</i> 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.