Diffusion in nonequilibrium two-dimensional crystals

Area of Science:

• Physics
• Statistical Mechanics
• Soft Matter Physics

Background:

• Absorbing state models are crucial for understanding systems with absorbing phases.
• Understanding phase transitions in systems with only repulsive interactions is complex.
• Dynamical models with random perturbations offer insights into self-organization.

Purpose of the Study:

• To investigate the phase behavior of a two-dimensional dynamical absorbing state model of monodisperse disks.
• To analyze the impact of repulsive interactions and random kicks on system dynamics and ordering.
• To characterize unconventional phase transitions and compare them to traditional order-disorder transitions.

Main Methods:

• Development of a two-dimensional dynamical absorbing state model.
• Simulation of monodisperse disks with repulsive displacement interactions.
• Analysis of phase transitions driven by a single parameter, maximum random kick size (ε).

Main Results:

• Identification of a phase diagram with unconventional features.
• Observation of a transition from a static disordered state to an active hexagonal crystal with ring diffusion.
• Further transition to an active isotropic liquid state.
• Demonstration that small ε promotes self-organization, while large ε hinders it.

Conclusions:

• Repulsive interactions alone can drive rich phase behavior and self-organization in dynamical systems.
• The observed transitions differ significantly from typical energy-entropy driven order-disorder transitions.
• The parameter ε uniquely controls self-organization, highlighting a novel mechanism for controlling system states.