Absence of solid phase in dense amorphous active granular matter

TL;DR

This study shows that active granular matter can remain fluid at high densities if crystallization is prevented, challenging the traditional view that dense granular matter inevitably solidifies due to jamming.

Contribution

It demonstrates that activity can suppress solid phase formation in dense granular systems by preventing crystallization through particle size mixing.

Findings

Active granular matter remains fluid at high packing fractions.

Crystallization prevention maintains fluidity despite high density.

Activity influences the global dynamical properties of granular matter.

Abstract

Solid phase of dense granular matter is inevitable because of jamming transition when the packing fraction or the pressure suffered is high enough. The experiment suggests that active Brownian granular matter will keep fluid phase even under the highest packing fraction (higher than the packing fraction of crystallization) if crystallization is prevented by mixing granular particles of different sizes. The findings encourage us to reconsider the role of activity in affecting the global dynamical properties of matter.