Critical Slowing of Fluctuations in a Nematic Liquid Crystal

We have used a high-resolution spherical Fabry-Perot interferometer and a single-frequency laser to measure the time dependence of local fluctuations of order in the isotropic phase of a nematic liquid crystal. We find a critical slowing of the fluctuations analogous to the critical slowing of spin fluctuations in a ferromagnet. The fluctuations relax exponentially with a single relaxation time τ. Over two decades of τ we find that τ∼ (T−Tc)−γ with γ≃43 and Tc slightly below the temperature at which the first-order transition to the nematic phase occurs.