Waves at the nematic-isotropic interface: the role of surface tension anisotropy, curvature elasticity, and backflow effects.

Recently, a theoretical description of waves at the nematic-isotropic interface has been proposed using a generalized dynamical Landau-Ginzburg-de Gennes theory [V. Popa-Nita and T. J. Sluckin, Phys. Rev. E 66, 041703 (2002)]. This calculation assumed an isotropic surface tension, i.e., independent of the director orientation at the interface and neglected all coupling between the director and the hydrodynamic flow. As a consequence, the director was assumed to keep a fixed orientation and do not couple with the oscillations of the interface. These assumptions are rather crude in real nematics where surface tension anisotropy may be as large as 20% and where hydrodynamic coupling with the director is known to be important. In this paper we propose to take into account these two effects: as a result, interface oscillations couple with the director field via hydrodynamic flows and backflow effects. We analyze how these phenomena change the dispersion relation. Finally, we review experiments on the nematic-isotropic interface and discuss how to measure experimentally the dispersion relation.