THEORY OF ORIENTATIONAL MODES AT A NEMATIC SOLID INTERFACE WHEN DO SURFACE-MODES APPEAR

Orientational modes at a solid-nematic interface with Rapini-Papoular boundary conditions are analysed in the framework of continuum nematodynamics, including the coupling of the director and fluid velocity. In the case of planar orientation, a surface mode appears in addition to the ordinary bulk modes, if the coupling between the director and fluid velocity, governed by the Leslie coefficient mu2, is large enough. The dispersion relation for the surface mode exhibits two distinctive regimes as mu2 increases. In a realistic situation, the relaxation rate of the surface mode is several times slower than that of the corresponding bulk mode.