Incollection,
Nonequilibrium pattern formation in chiral liquid crystal films
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
Liquid crystal films exhibit various spatial patterns in equilibrium
or spatio-temporal ones in nonequilibrium states. It has been observed
that orientations of liquid crystal molecules in chiral smectic films
collectively rotate when the transmembrane vapor flux exists and this
rotation causes formation of macroscopic patterns (Y. Tabe and H. Yokoyama,
Nature Mater. vol.2 (2003) p.806). This phenomenon can be understood as
a two-dimensional analogue of the Lehmann effect which is explained as
a result of a peculiar dynamical coupling due to chirality between a
certain flux and torque. However, simple Lehmann-type models do not
explain enough the observed phenomena. In such models the observed
patterns are only due to the boundary effect.
Here we propose a model with two order parameters, introducing a chiral
order parameter field in addition to the so-called c-vector field which
denotes the in-plane orientation of the liquid crystal molecules. In terms
of these two fields we construct a phenomenological model which describes
nonequilibrium dynamics of chiral liquid crystal films. Using this model,
we show numerically that a finite amplitude perturbation causes
self-organized formation of the target patterns associated with the
orientation which is observed in the experiments.
