Growing dynamical facilitation on approaching the random pinning colloidal glass transition

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• The fundamental origin of the glass transition (thermodynamic vs. dynamic) remains debated.
• Dynamical Facilitation (DF) theory offers a dynamic perspective but lacks experimental validation.
• Vitrification simulations suggest a thermodynamic phase transition, yet DF remains unexplored in this context.

Purpose of the Study:

• To experimentally investigate Dynamical Facilitation in colloidal glass-forming liquids.
• To explore the relationship between DF, liquid density, and particle pinning.
• To examine the emergence of heterogeneous dynamics within the DF framework.

Main Methods:

• Utilized video microscopy for observing particle dynamics.
• Employed holographic optical tweezers to manipulate and pin particles.
• Analyzed colloidal glass-forming liquids under varying density and pinning conditions.

Main Results:

• Demonstrated that Dynamical Facilitation increases with both liquid density and the fraction of pinned particles.
• Observed the emergence of string-like cooperative motion, characteristic of heterogeneous dynamics, within the DF model.
• Provided the first experimental evidence linking DF to density and pinning.

Conclusions:

• Findings suggest that Dynamical Facilitation is influenced by system density and particle immobilization.
• The emergence of heterogeneous dynamics supports the facilitation concept.
• A comprehensive understanding of the glass transition may require integrating thermodynamic and dynamic theoretical approaches.