Linear and non-linear transient patterns in the splay Freedericksz transition of nematics

Agnes Buka Lorenz Kramer

doi:doi:10.1051/jp2:1992136

Numéro		J. Phys. II France Volume 2, Numéro 3, March 1992


Page(s)		315 - 326
DOI		https://doi.org/10.1051/jp2:1992136

DOI: 10.1051/jp2:1992136
J. Phys. II France 2 (1992) 315-326

Linear and non-linear transient patterns in the splay Freedericksz transition of nematics

Agnes Buka Lorenz Kramer^{1, 2}

¹ Central Research Institute for Physics of the Hungarian Academy of Sciences, P.O.B. 49, H-1525 Budapest, Hungary
² University of Bayreuth, Institute of Physics, P.O.B. 101251, W-8580 Bayreuth, Germany

(Received 2 September 1991 1991, accepted 13 December 1991)

Abstract
A three-dimensional linear analysis of transient patterns occuring during the splay Freedericksz transition is presented including contributions relevant for the electrically driven case. The most rapidly growing modes have a wave vector predominantly along the initial directore alignment. The onset of the pattern formation is compared with the results of a nonlinear calculation carried out previously for the wave vector in the perpendicular direction. This shows that the nonlinear effect is the relevant mechanism for large dielectric anisotropy whereas for low anisotropy the linear pattern is favored. Preliminary experiments have been carried out with electric and magnetic fields using two materials with high and low dielectric anisotropy. Both, linear and nonlinear structures were found. A transition between the two types of patterns induced by changing the frequency of the applied electric field is presented.