Nonlinear transports and microvortex excitations in sheared quasi-two-dimensional dust Coulomb liquids - art. no. 016402

The microscopic spatiotemporal response of a quasi-two-dimensional dust Cou lomb liquid to the shear induced by a cw laser is investigated through opti cal microscopy. The dust Coulomb liquid consists of many micrometer sized d ust particles char,aed and suspended in a low pressure rf discharge backgro und. Assisted by thermal fluctuations, the laser forcing enhances the casca ded generation of irregular vortices through reducing caging barriers for c ollective hopping. The vortex mixing leads to the mean velocity field with a simple structure that has a strong shear along the edge of the narrow las er beam. It also promotes the anomalous transverse diffusion with decaying strength from the line sourer. The viscosity and diffusion coefficient both show nonlinear dependence on the laser power under the interplay among the above nonlinear excitation and relaxation processes.