7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Percolating transition from order to disorder in two-dimensional Yukawa system
Wei-Shuo Lo, Hao-Wei Hu, and Lin I
Department of Physics and Center for Complex Systems,
National Central University, Jhongli 32001, Taiwan
Email (speaker): loweishuo@gmail.com
Percolation is a phenomenon in which a network isformed by connecting active or inactive sites, and it iscommonly observed in various non-equilibrium systems
that are influenced by different control parameters.
Percolation of liquids through porous material, the failureof power grids, the spread of forest fires and epidemics,
and the transition to turbulence in hydrodynamic andnonlinear wave systems are a few good macroscopic
systems exhibiting percolation transition [1].
In passive coupled many-body systems in the
microscopic discrete level, such as cold liquids and solids,
there is a dynamic interplay between the emergence oforder through mutual coupling and the disruptive effectsof thermal agitation. This interplay gives rise to theformation and dissolution of local ordered (disordered)microstructures and motion. Recent researches haveshown that phenomena such as the clustering of cooled
liquids into gels [2], the yielding of glasses under external
stress [3], and the layering of liquids induced byconfinement [4], exhibit similar transition behaviors thatcan be explained by percolation theory. These findings
highlight the presence of generic transition phenomena inthese systems.
Melting of a crystal in two dimensions (2D) is
associated with the dissociation of topological defects.
These topological defects destroy the order of crystals.
The KTHNY-theory predicts two continuous phasetransitions from the crystalline to the liquid phase, throughthe intermediate hexatic phase, associated with the loss ofthe translational order, followed by the loss of theorientational order [5]. However, with increasing
temperature, how localized disordered sites emerge,
spread and aggregate into a lager disordered domain, still
remains an unexplored question.
In this work, the above issues are numericallyaddressed in a 2D Yukawa system, through Langevin-typemolecular dynamic simulation with periodic boundarycondition. Localized ordered sites (LOSs) and disorderedsites (LDSs) are identified based on the local bondorientational order. It is found that with increasing
temperature, the transition from the solid to the liquid
phase through the hexatic phase are associated with thesporadic emergence, spreading, and termination of LDSs
in the form of multiscale clusters in the xyt space. The area
fraction of LOSs also exhibits a transition from thegradual rise to a smooth rapid rise at the solid-hexatic
transition, followed by a transition to a smooth slow riseat the hexatic-liquid transition. The defect cluster
percolates in the xyt space at the hexatic-liquid transition.
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19 2457 (1979); A. P. Young, Phys. Rev. B 19 1855 (1979)