Dynamical coexistence in moderately polydisperse hard-sphere glasses

Area of Science:

• Condensed Matter Physics
• Statistical Mechanics
• Computational Physics

Background:

• Understanding the glass transition is crucial for materials science.
• Hard-sphere models provide a simplified yet powerful framework for studying phase transitions.
• Polydispersity in particle size significantly impacts the dynamics of glass-forming systems.

Purpose of the Study:

• To investigate the dynamical-structural phase transition in a 10% polydisperse hard-sphere fluid.
• To characterize the nature of the transition and the coexistence of distinct dynamical phases.
• To explore the critical behavior and universality class of the observed transition.

Main Methods:

• Extensive numerical simulations using event-driven molecular dynamics.
• Sampling trajectories from a fixed observation time ensemble.
• Finite-size scaling analysis of exceptionally long trajectories.

Main Results:

• Identification of a dynamical-structural (active-inactive) phase transition.
• Observation of coexistence between liquid-like (low order) and glass-like (high order) trajectories.
• Demonstration of a spatiotemporal interface separating the two phases.
• Agreement with Binder's scaling theory for first-order transitions.
• Evidence for a critical point controlling dynamic arrest, with narrowing coexistence regions at higher densities.

Conclusions:

• The hard-sphere fluid exhibits distinct dynamical phases with a clear phase transition.
• The transition is characterized by coexistence and a spatiotemporal interface.
• Critical behavior aligns with the universality class of directed percolation in 3+1 dimensions, suggesting universal mechanisms govern dynamic arrest.