Observation of thermal fluctuations of disclination lines in a nematic liquid crystal.

ABSTRACT

We present measurements of the line tension and the viscous drag of a disclination line in nematic liquid crystal via observation of thermal fluctuations of the line position. Fourier analysis of the displacement of a disclination line due to thermal fluctuations was used to obtain the amplitudes and the relaxation rates of eigenmodes of the fluctuations. From them the line tension and the viscous drag were deduced. Our measurements show the coupling between flow and nematic orientation affects the viscous drag considerably, while the values of the line tension agree with a simple theory already predicted by de Gennes.