Morphologies and dynamics of the interfaces between active and passive phases.

Area of Science:

• Soft Matter Physics
• Nonequilibrium Statistical Mechanics
• Complex Systems

Background:

• Active matter systems display unique collective behaviors and phases, crucial for studying nonequilibrium physics.
• While motility-induced phase separation in active-passive mixtures is studied, the interface morphology remains underexplored.

Purpose of the Study:

• Investigate the interface morphology in 2D mixtures of active and passive particles.
• Determine the phase diagram of the active-passive interface by varying Péclet number (Pe) and area fraction (ρ).
• Analyze the dynamic scaling and interfacial growth mechanisms.

Main Methods:

• Brownian dynamics simulations were employed to model the active-passive particle mixtures.
• Systematic variation of Péclet number (Pe) and area fraction (ρ) to map the phase diagram.
• Dynamic scaling analysis and capillary wave theory were used to characterize interface behavior.

Main Results:

• Identified three interface morphologies: rough sharp, rough invasive, and flat interdiffusive.
• Observed anomalous dynamic scaling (z = α/(β - κ)) for sharp interfaces, deviating from conventional universality classes.
• Interface propagation follows t^(1/2) scaling, with superdiffusion during relaxation, distinct from passive interfaces.

Conclusions:

• The study elucidates the distinct interfacial dynamics in active-passive systems compared to passive ones.
• Anomalous scaling suggests unique roughening mechanisms in active matter interfaces.
• Findings contribute to understanding nonequilibrium phenomena and interfacial growth in active matter.