Dynamic phases and combing effects for elongated particles moving over quenched disorder

Area of Science:

• Physics
• Materials Science
• Soft Matter Physics

Background:

• Elongated particles exhibit complex dynamics when driven over disordered landscapes.
• Pinning sites introduce heterogeneity, influencing particle self-organization and collective behavior.

Purpose of the Study:

• To investigate the dynamic phases and emergent ordering of elongated particles in a 2D system with random pinning sites.
• To understand the influence of pinning site density, drive magnitude, and particle elongation on system dynamics.

Main Methods:

• Simulations of a two-dimensional system of driven elongated particles.
• Analysis of dynamic phases based on nematic ordering, cluster size, number of pinned particles, and transverse diffusion.
• Systematic variation of pinning site density, external drive, and particle elongation.

Main Results:

• Observed diverse dynamic phases: random structures, stripe/combed phases with nematic order, and clogged states.
• Identified a 'combing effect' where pinning enhances particle alignment, leading to optimal nematic ordering at specific drive and density combinations.
• Found that high drives reduce the combing effect, while strong pinning leads to heterogeneous clustered/clogged states that depin into high-diffusion states.

Conclusions:

• Particle-pinning interactions create rich phase diagrams for driven elongated systems.
• The interplay between pinning, drive, and particle shape dictates emergent collective behavior and ordering.
• Pinning can be leveraged to enhance particle alignment, but excessive pinning leads to jamming and altered dynamics.