;Microscopically, unlike intuitive expectation, the cold liquid around freezing is not completely disordered. The competition between the strong particle interaction and weak thermal agitation leads to the heterogeneous structure with coexisting crystalline ordered domains and surrounding defect clusters, and heterogeneous dynamics with alternating particle rattling in the caging wells of nearest neighbor particles and cooperative particle hopping which induces structural rearrangements. Namely, the cold liquid can be viewed as a patchwork of crystalline ordered domains, which partially possesses solid like behavior but can still be rearranged under thermal agitation or external stress. In this work, through direct experimental microscopic visualization of cold dusty plasma liquid and numerical simulation of cold Yukawa liquids, we address the following important unexplored fundamental issues. (1) What is the cooperative motion existing in cold liquids, (2) How is structure rearranged through the cooperative motion, (3) whether the growth of crystalline ordered domains in crystallization and cold liquids are similar, (4) what is the generic flow behavior of cold liquids under various applied stresses, and (5) what is the avalanche dynamics of cracking of crystalline ordered domains in the weakly stressed cold liquid?
It is found, using a novel bond-dynamics analysis, the cooperative motion in cold liquids can be categorized into static patches, rotating patches, drifting patches, and shear strips located at the interface of co-rotating patches, beyond the earlier ﬁndings of the cooperative hopping strings and bands. The structural evolution is thereby accomplished by the drifting, rotation, rupture, and healing of crystalline ordered domains. In addition, the similar domain rotation, regarded as the kinetic origins of grain coalescence, is found in the crystallization of quenched two dimensional Yukawa liquids. Furthermore, suffering to the external stress which provides local force and torque, the above cooperative processes are enhanced persistently. Strong applied stress can cause the formation of the shear band with a higher averaged forward displacement and coherent vortical excitations. However, under weak stress, crystalline ordered domains either crack and heal in the loading zone, or temporally sustain and propagate stress to remote regions for avalanche cracking. The spatiotemporal behaviors of the avalanche cracking are discussed through the collision of dislocations with mismatched Burgers vectors, which is the key to generate the large crack clusters inside a crystalline ordered domain.