A homeotropic nematic liquid crystal was exposed to low frequency oscillatory shear (Couette flow). In the presence of rectilinear shear a stationary roll pattern was found above a critical amplitude (Ar). In case of elliptical excitation a spatially nonuniform slow rotation of the director was observed, which lead to the propagation of the so called phase waves in two different systems: in a two-phase (nematic-isotropic) system and in a homeotropic nematic layer in the presence of a destabilizing external electric field. Phase waves also have been observed in the ultrasonic frequency range at much smaller shear amplitudes.
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