S. Sukumaran et Gs. Ranganath, DYNAMICS OF KINKS IN SMECTIC-C LIQUID-CRYSTALS IN PERIODICALLY VARYING EXTERNAL FIELDS, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 56(2), 1997, pp. 1791-1803
We have considered the dynamics of kinks in smectic-C liquid crystal i
n uniformly rotating and oscillating electric or magnetic fields. In t
ilted oscillating fields our results are at variance with those of ear
lier investigations which predict chaos in this geometry for a pi kink
. On the other hand, we find that the velocity and the structure of a
pi kink are oscillatory with the frequency of the varying held. The av
erage velocity as a function of the tilt angle of the field indicates
a threshold angle beyond which there is a crossover in velocity select
ion with the system choosing from a family of solutions. Surprisingly,
in a nonoscillating field rotating in a plane normal to the layers, a
pi kink has a drift velocity whose direction is dependent upon the se
nse of rotation. As a result of this, a 2 pi kink could be in a bound
oscillating state or it could split itself into two oppositely driftin
g oscillating pi kinks. In a nonoscillating tilted field rotating abou
t the layer normal, in the synchronous regime we find an instability o
f a kink connecting a stable state and a metastable state. In the asyn
chronous regime, a kink connecting two stable states has aperiodic mot
ion. Interestingly, in the same geometry in oscillating fields, we End
that a kink joining a stable state and a metastable state is more sta
ble. In this geometry, periodic and aperiodic fluctuating kink structu
res are also possible. We have suggested a simple way of understanding
the general dynamical features of a kink on the basis of the dynamics
of the uniform director state which is found to be very sensitive to
parameters of the system.