Emergent collective phenomena in a mixture of hard shapes through active rotation

TL;DR

This study explores how active rotation of concave hard particles leads to unique collective behaviors like phase separation and rotating crystal formation, revealing new non-equilibrium phenomena.

Contribution

It demonstrates that active rotation induces effective interactions and novel phase behaviors in hard particle systems, distinct from linear propulsion or equilibrium states.

Findings

Active rotation causes phase separation via spinodal decomposition.

Formation of rotating crystal structures observed.

Super-diffusive motion along interfaces transports inactive particles.

Abstract

We investigate collective phenomena with rotationally driven spinners of concave shape. Each spinner experiences a constant internal torque in either a clockwise or counterclockwise direction. Although the spinners are modeled as hard, otherwise non-interacting rigid bodies, we find that their active motion induces an effective interaction that favors rotation in the same direction. With increasing density and activity, phase separation occurs via spinodal decomposition, as well as self-organization into rotating crystals. We observe the emergence of cooperative, super-diffusive motion along interfaces, which can transport inactive test particles. Our results demonstrate novel phase behavior of actively rotated particles that is not possible with linear propulsion or in non-driven, equilibrium systems of identical hard particles.