Defect-mediated phase transitions in active soft matter.

Area of Science:

• Physics
• Complex Systems
• Statistical Mechanics

Background:

• Active matter systems exhibit unique collective behaviors driven by self-propulsion.
• Topological defects are crucial for understanding order and phase transitions in various physical systems.
• The role of topological defects in active matter, particularly concerning order, remains an active area of research.

Purpose of the Study:

• To investigate the impact of topological defects on the degree of order in active matter.
• To explore how different interaction parameters influence the emergence and behavior of order in self-propelled particle systems.

Main Methods:

• Utilized an agent-based model to simulate self-propelled particles.
• Incorporated polar alignment and short-ranged repulsive interactions into the model.
• Analyzed system behavior under varying strengths of alignment and repulsive forces.

Main Results:

• Strong alignment forces resulted in collectively moving polycrystalline states with dynamic grain boundaries.
• When repulsive forces dominated, active system fluctuations induced quasi-long-range transitional order.
• Notably, the repulsive force regime achieved transitional order without the formation of topological defects, contrasting with thermal systems.

Conclusions:

• The interplay between alignment and repulsion dictates the nature of order in active matter.
• Active matter can exhibit complex ordered states, including transitional order, even in the absence of topological defects.
• Findings contribute to understanding non-equilibrium phase transitions and the unique properties of active systems.