Down to the discrete microscopic level, the liquid is neither homogeneous nor completely disordered. The interplay of mutual coupling and thermal agitation makes the system support short range structural order, and avalanche-type cooperative hopping excitations which lead to structural arrangement. The rich dynamical behaviors of spatio-temporal heterogeneities are still poorly understood because of the lack of proper tools for direct visualization. The dusty plasma liquid can be self-organized by negatively charged micrometer sized dusts suspending in a low-pressure rf discharge background. Its sub-mm inter-particle distance and the tens of second thermal relaxation time make it a proper system to mimic and understand the generic spatio-temporal behaviors of the liquid at the discrete kinetic level through direct optical video-microscopy. In this paper, we briefly review the recent studies on the dynamical heterogeneities of the cold 2D dusty plasma liquids at the discrete level. The effects of mutual interaction, thermal agitation, external shear, and tight confinement on micro-motion, anomalous diffusion, avalanche-type excitations of hopping clusters and defect clusters, structural ordering and rearrangement, and visco-elastic responses are presented and discussed.
We report a direct experimental observation of traveling microbubbles induced by intense laser pulses in strongly coupled dusty plasma liquids. The dense plasma ablated from a suspended dust particle generates a spherical plasma bubble with a low dust density, in the quiescent regime before a transition to self-organized longitudinal dust density waves. It travels downwards at a velocity about 6 cm/sec inside the dust liquid. Dust density fluctuations trailing the bubble are also observed. The bubble generated in the high pressure dissipative regime collapses right after formation.
Through direct visualization at the discrete level, the microexcitations in cold 2 + 1D dusty plasma liquids formed by negatively charged dusts suspended in low pressure gaseous discharges were experimentally investigated, in which the downward ion flow wake field induces strong vertical coupling and chain bundle structure. It is found that the horizontal structure and motion are similar to those of the two-dimensional liquid. Different types of basic cooperative chain excitations: straight vertical chains with small amplitude jittering, chain tilting-restraightening, bundle twisting-restraightening, and chain breaking-reconnection, are observed. The region with good ͑poor͒ horizontal structural order prefers the straight ͑tilted or broken͒ chains with little ͑large͒ titling and tilting rate.
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