Glass Transition and Jamming in a Driven Granular System
Collective behavior of granular particles is often markedly different from that of ordinary solids, liquids, or gases, due to the dissipative nature of interactions such as inelastic collisions and friction. Recent studies revealed, however, that driven granular systems, where vibration, shear, or airflow compensates the energy dissipation, exhibit crystallization and a liquid-glass transition, which are strikingly analogous to those in molecular liquids and colloidal suspensions. Here we use a vibrated quasi-two-dimensional granular system as a model of microscopic thermal systems, and investigate the origin of the liquid-glass transition, which remains one of the most fundamental unsolved problems in condensed matter physics. We demonstrate by direct observation the existence of long-lived medium-range crystalline order, whose size grows monotonically towards the ideal glass-transition point. Furthermore, we find a close relationship of this crystalline order with both dynamic heterogeneity and slow dynamics, which are considered to be the keys to this problem. Our findings are remarkably similar to recent numerical results on two distinct model liquids with thermal fluctuations, and thus open an intriguing possibility of understanding the dynamic arrest in both thermal and athermal systems in a unified manner.