Dynamical processes of interstitial diffusion in a two-dimensional colloidal crystal

Area of Science:

• Condensed Matter Physics
• Materials Science
• Statistical Mechanics

Background:

• Point defects (vacancies, interstitials) are topological defect bound states in 2D solids.
• Their role in system thermodynamics is significant, yet their dynamics are poorly understood.
• 2D colloidal crystals offer a model system for real-time defect dynamics study.

Purpose of the Study:

• Investigate the dynamical processes of interstitials in 2D colloidal crystals.
• Quantify diffusion constants of mono- and diinterstitials.
• Explore the symmetry and lattice distortion associated with interstitial defects.

Main Methods:

• Utilized video microscopy to observe real-time dynamics of defects in 2D colloidal crystals.
• Measured diffusion constants for mono- and diinterstitials.
• Analyzed the positional patterns of disclinations relative to defect centers.

Main Results:

• Diffusion constants of interstitials (mono- and di-) are significantly higher than vacancies.
• Diinterstitials diffuse slower than monointerstitials.
• Monointerstitials exhibit sixfold symmetry, indicating equilibrium and local detailed balance.
• Diinterstitials do not show this symmetry within the observed window, suggesting severe, slow-recovering lattice distortions.

Conclusions:

• Interstitials play a crucial role in the dynamics of 2D colloidal crystals.
• The observed symmetry breaking by diinterstitials suggests a pathway to inducing local lattice melting.
• This research provides a foundation for microscopic studies on melting dynamics in model systems.