Crystallization Dynamics of a Single Layer Complex Plasma

We report a series of complex (dusty) plasma experiments, aimed at the study of the detailed time evolution of the recrystallization process following a rapid quench of a two-dimensional dust liquid. The experiments were accompanied by large-scale (million-particle) molecular dynamics simulations, assuming Yukawa-type interparticle interaction. Both experiment and simulation show a $\propto t^{\alpha }$ (power-law) dependence of the linear crystallite domain size as measured by the bond-order correlation length, translational correlation length, dislocation (defect) density, and a direct size measurement algorithm. The results show two stages of order formation. On short time scales, individual particle motion dominates; this is a fast process characterized by $\alpha =0.93\pm 0.1$. At longer time scales, small crystallites undergo collective rearrangement, merging into bigger ones, resulting in a smaller exponent $\alpha =0.38\pm 0.06$.

Figure 1

Illustration of the data evaluation process for a liquid (left column) and a solid (right column) using snapshot data from the experiment. Row (a): Particle positions as identified in the raw images. Rows (b) and (c): Magnitude and complex phase angle, respectively, of $G_6(r)$ bond-order parameter. Rows (d) and (e): $|g(r)-1|$ (pair) and $g_6(r)$ (bond-order) correlation functions of the sample snapshots involving particles situated within the red circles in (a).

Figure 2

Time evolution of the correlation lengths ${\xi }_6$ (red squares), ${\xi }_g$ (green circles), and the inverse defect fraction $1/D$ (blue triangles) for a single, representative freezing cycle. Lines represent linear fits on a log-log plot for the short and long time domains.

Figure 3

Time evolution of the correlation lengths ${\xi }_6$ and ${\xi }_g$, the inverse defect fraction $1/D$, and the size measured with the flood fill algorithm from MD simulation. Time is normalized to the 2D nominal plasma frequency ${\omega }_0=\sqrt{n{Q}^2/2{\epsilon }_{0}ma}$. Points are shifted for clarity.