DYNAMICS OF KINKS IN SMECTIC-C LIQUID-CRYSTALS IN PERIODICALLY VARYING EXTERNAL FIELDS

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.