Solitons and defects in nematic liquid crystals under a simple shear flow and in a static external magnetic field
Luo Kai-Fu(罗开富)†, Jiang Xiu-Li(蒋秀丽), and Yang Yu-Liang(杨玉良)
Department of Macromolecular Science, Key Laboratory of Molecular Engineering of Polymers of State Ministry Education, Fudan University, Shanghai 200433, China
Abstract Under a simple shear flow and in a static external magnetic field, the production of defects in the director-aligning regime of nematic liquid crystals has been investigated in terms of the Leslie--Ericksen theory. The equation of motion of the nematic director, which conforms to the driven over-damped sine-Gordon equation, has a soliton solution of the amplitude $\pi$. We show that the stationary state with the director uniformly oriented at a Leslie angle is only a metastable state and the potential, which governs the motion of the director, has a number of stable stationary states. For a strong magnetic field, the higher energy barrier between the stable and unstable states leads the director to be locked along the magnetic field direction. However, at the appropriate shear rate and magnetic field the defects, which appear as a stable solitary solution, can be nucleated from a uniformly aligned nematic liquid crystal. We have calculated the stationary travelling velocity of the solitary waves and the distance between a pair of defects.
Received: 11 September 2007
Revised: 03 March 2008
Accepted manuscript online:
(Continuum models and theories of liquid crystal structure)
Fund: Project
supported by the National Natural Science Foundation of China (Grant
No 29874011) and State Basic Research Program of China (Grant No
1999064800).
Cite this article:
Luo Kai-Fu(罗开富), Jiang Xiu-Li(蒋秀丽), and Yang Yu-Liang(杨玉良) Solitons and defects in nematic liquid crystals under a simple shear flow and in a static external magnetic field 2008 Chin. Phys. B 17 2600
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