Title:	Effect of an electric field on defects in a nematic liquid crystal with variable surface anchoring
Authors:	Kumar, Arun T. Sastry, V.S.S. Ishikawa, Ken Takezoe, Hideo Madhusudana, N.V. Dhara, Surajit
Keywords:	Defects Surface Anchoring Annihilation Boojums
Issue Date:	Aug-2011
Publisher:	Taylor & Francis
Citation:	Liquid Crystals, 2011, Vol.38, p971
Abstract:	We report experimental studies on defects in a nematic liquid crystal with negative dielectric anisotropy mounted in a cell with perfluoropolymer-coated surfaces. The sample exhibits a discontinuous anchoring transition from planar to homeotropic on cooling at zero or a small electric field, and above a cross-over voltage a continuous ‘inverse Freedericksz transition’, at which the director starts tilting in opposite directions at the two surfaces. Defects of strength ±1/2 are either annihilated or expelled when the director tilts. On the other hand, disclination lines of ±1 which end in partial point defects (boojums) at the surfaces in the planar alignment regime acquire point defects of strength ±1 at the midplane of the cell when the director tilts. At a low enough temperature, the homeotropic anchoring becomes strong, and an electric field above the Freedericksz threshold generates the usual umbilic defects, which follow the dynamic scaling laws found in earlier studies.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/4160
ISSN:	0267-8292 1366-5855 (online)
Alternative Location:	http://dx.doi.org/10.1080/02678292.2011.587962
Copyright:	2011 Taylor & Francis
Appears in Collections:	Research Papers (SCM)

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