Shear-induced orientational ordering in an active glass former

Area of Science:

• Physics
• Soft Matter Physics
• Complex Systems

Background:

• Dense active matter systems, or active glasses, are disordered, out-of-equilibrium systems found across various scales.
• These systems display unique dynamical and mechanical properties due to self-propulsion and structural disorder.

Purpose of the Study:

• To identify and differentiate dynamical steady states in a sheared model active glassy system.
• To develop an analytical theory explaining shear-induced ordering in active glasses without explicit aligning interactions.

Main Methods:

• Extensive molecular dynamics simulations were employed.
• Dynamical and mechanical order parameters were utilized to analyze system behavior.
• An analytical theory based on a single-particle Fokker-Planck description was developed.

Main Results:

• Three distinct dynamical steady states were identified: disordered, propulsion-induced ordered, and shear-induced ordered.
• A novel mechanism for shear-induced orientational ordering in active glasses was rationalized.
• The theory accurately predicted particle position and orientation distributions observed in simulations.

Conclusions:

• Steady shear flow can induce orientational ordering in active glasses, even without direct aligning forces.
• The developed Fokker-Planck theory provides a framework for understanding and predicting active glass behavior under shear.
• Results are relevant for experimental studies on the rheology of active colloids and granular matter.