Intershell and configurational properties of two-dimensional dust crystals in complex plasmas*

Intershell dynamics of two-dimensional (2D) charged particle systems have been extensively researched in condensed matter physics. Due to their quantum scales, pure Coulomb crystals are extremely fragile to produce experimentally and are generally studied via simulations and numerical methods. However, complex/dusty plasmas can serve as classical analogs, where charged dust particles can be of micro-meter size, enabling direct visualization of individual particles. In 2D complex plasma, particles interact with screened-Coulomb potential rather than pure Coulomb but exhibit similar shell structures and six-fold hexagonal symmetry. We used experimental methods presented in the reference [1] to obtain 2D finite dust crystals, called N-Clusters, where N can be of any desired value between one to any large number. We further studied the evolution of crystalline intershell structure from N = 1 to 50 with dN = 1. A few N-Clusters were then perturbed with multiple heating and cooling cycles using randomized laser beams to extract configurational entropy and statistically obtained ground and meta-stable states of a specific N-Cluster. We also compared our experiments with published simulation results.

[1] Kumar, R., et al., Rev. Sci. Instrum. 95, 053503 (2024)