Competing effect of disorder on phase separation in active systems.

Area of Science:

• Soft Matter Physics
• Statistical Mechanics
• Non-equilibrium Systems

Background:

• Self-propelled particles (SPPs) exhibit complex emergent behaviors.
• Motility-induced phase separation (MIPS) is a key phenomenon in active matter.
• The role of quenched disorder in SPP systems is not fully understood.

Purpose of the Study:

• Investigate the impact of random pinned disorder on SPPs.
• Characterize phase transitions and emergent structures in disordered SPP systems.
• Determine how disorder affects phase separation and particle dynamics.

Main Methods:

• Developed a continuum model using coupled hydrodynamic equations for density and momentum.
• Employed numerical simulations to explore the phase space.
• Utilized linearized approximation for phase diagram construction.
• Analyzed structure factor and fractal dimension to quantify interfaces.

Main Results:

• Weak disorder induces phase separation at lower densities and activities than typical MIPS.
• Increasing disorder leads to microphase separation, heterogeneity, and kinetic arrest.
• Strong disorder increases domain interface roughness and suppresses number fluctuations.
• Fractal dimension analysis reveals increasing irregularity of phase-separated domains.

Conclusions:

• Random pinned disorder significantly alters the phase behavior of SPPs.
• Disorder can drive phase separation and arrest dynamics, offering new routes to control active matter.
• The study provides a phase diagram and insights into interface properties in disordered active systems.