Correlating structural order with structural rearrangement in dusty plasma liquids: can structural rearrangement be predicted by static structural information?

Multiscale Coherent Excitations in Microscopic Acoustic Wave Turbulence of Cold Dusty Plasma Liquids

We experimentally demonstrate the observation of thermally excited microscopic acoustic wave turbulence at the discrete level in quasi-two-dimensional cold dusty plasma liquids. Through multidimensional empirical mode decomposition of individual dust particle motions over a large area, the turbulence is decomposed into multiscale traveling wave modes, sharing self-similar dynamics. All modes exhibit intermittent excitation, propagation, scattering, and annihilation of coherent waves, in the form of clusters in the xyt space, with cluster sizes exhibiting self-similar power law distribution. The poor particle interlocking in the region with poor structural order is the key origin of the easier excitations of the large amplitude slow modes. The sudden phase synchronization of slow wave modes switches particle motion from cage rattling to cooperative hopping.

Disentangling defects and sound modes in disordered solids

We develop a new method to isolate localized defects from extended vibrational modes in disordered solids. This method augments particle interactions with an artificial potential that acts as a high-pass filter: it preserves small-scale structures while pushing extended vibrational modes to higher frequencies. The low-frequency modes that remain are "bare" defects; they are exponentially localized without the quadrupolar tails associated with elastic interactions. We demonstrate that these localized excitations are excellent predictors of plastic rearrangements in the solid. We characterize several of the properties of these defects that appear in mesoscopic theory of plasticity, including their distribution of energy barriers, number density, and size, which is a first step in testing and revising continuum models for plasticity in disordered solids.

Avalanche structural rearrangement through cracking-healing in weakly stressed cold dusty plasma liquids

We experimentally investigate the spatiotemporal dynamical behaviors of the avalanche structural rearrangement through micro-cracking-healing in weakly stressed cold dusty plasma liquids, and the kinetic origins for their different spatial and temporal classifications. The crystalline ordered domains can be cracked or temporarily sustain and transfer the weak stress to remote regions for cracking-healing. It is found that cracking sites form a fractal network with cluster size following power law distribution in the xyt space. The histograms of the persistent times for sustaining regional ordered and disordered structure, the temporal cracking burst width, and quiescent time between two bursts all follow power law decays with fast descending tails. Cracking can be classified into a single temporal burst with simple line like spatial patterns and the successive cracking fluctuation with densely packed cracking clusters. For an ordered region, whether the Burgers vectors of the incoming dislocations from the boundary allow direct dislocation reduction is the key for the above two classifications through cracking a large ordered domain into medium scale corotating ordered domains or small patches. The low regional structural order at the end of a cracking burst can be regarded as an alarm for predicting the short quiescent period before the next cracking burst.

Cooling the two-dimensional short spherocylinder liquid to the tetratic phase: Heterogeneous dynamics with one-way coupling between rotational and translational hopping

We numerically demonstrate the transition from the isotropic liquid to the tetratic phase with quasilong-range tetratic alignment order (i.e., with nearly parallel or perpendicular aligned rods), for the cold two-dimensional (2D) short spherocylinder system before crystallization and investigate the thermal assisted heterogeneous rotational and translational micromotions. Comparing with the 2D liquid of isotropic particles, spherocylinders introduce extra rotational degrees of freedom and destroy packing isotropy and the equivalence between rotational and translational motions. It is found that cooling leads to the stronger dynamical heterogeneity with more cooperative hopping and the stronger retardations of rotational hopping than translational hopping. Under topological constraints from nearly parallel and perpendicular rods of the tetratic phase, longitudinal and transverse translational hopping can occur without rotational hopping, but not the reverse. The empty space trailing a neighboring translational hopping patch is needed for triggering the patch rotational hopping with its translational motion into the empty space. It is the origin for the observed increasing separation of hopping time scales and the one-way coupling between rotational and translational hopping. Strips of longitudinally or transversely aligned rods can be ruptured and reconnected with neighboring strips through buckling, kink formation, and patch rotation, under the unbalanced torques or forces from their neighboring rods and thermal kicks.

Stress-induced microcracking and cooperative motion of cold dusty plasma liquids

We investigate the microresponse of the quasi-two-dimensional dusty plasma liquid around freezing to the shear force from a laser beam through the center of the liquid cluster. It is found that the cold liquid can be viewed as a patchwork of crystalline ordered domains (CODs) which are solidlike but can be cracked and rearranged by weak thermal agitation and external stress, through COD rotations and drifting. Under weak external stress comparable to thermal agitation, the laser zone is not the preferred region mastering cracking initiation. CODs in the laser zone can either break locally, or sustain and propagate the stress to remote regions for cracking, in the form of intermittent bursts. The COD rotation and drifting induced by the persistent torques and momentum from the stress causes the formation of the center shear band with a higher longitudinal speed. Increasing stress can enhance cracking initiation around the shear zone and then spread to other remote regions. It deteriorates the local structural order and causes strong shear banding dominated by longitudinal cooperative hopping.