Roles of energy dissipation in a liquid-solid transition of out-of-equilibrium systems

TL;DR

This study experimentally investigates how energy dissipation influences the liquid-solid transition in driven granular systems, revealing that strong inelasticity causes a shift from continuous to discontinuous phase transitions, highlighting dissipation's pivotal role in non-equilibrium self-organization.

Contribution

It demonstrates experimentally that dissipation alters the nature of phase transitions in driven granular matter, providing new insights into non-equilibrium self-organization mechanisms.

Findings

Strong inelasticity induces a first-order-like transition.

Coexistence of phases with different effective temperatures.

Dissipation fundamentally changes transition characteristics.

Abstract

Self-organization of active matter as well as driven granular matter in non-equilibrium dynamical states has attracted considerable attention not only from the fundamental and application viewpoints but also as a model to understand the occurrence of such phenomena in nature. These systems share common features originating from their intrinsically out-of-equilibrium nature. It remains elusive how energy dissipation affects the state selection in such non-equilibrium states. As a simple model system, we consider a non-equilibrium stationary state maintained by continuous energy input, relevant to industrial processing of granular materials by vibration and/or flow. More specifically, we experimentally study roles of dissipation in self-organization of a driven granular particle monolayer. We find that the introduction of strong inelasticity entirely changes the nature of the liquid-solid transition from two-step (nearly) continuous transitions (liquid-hexatic-solid) to a strongly discontinuous first-order-like one (liquid-solid), where the two phases with different effective temperatures can coexist, unlike thermal systems, under a balance between energy input and dissipation. Our finding indicates a pivotal role of energy dissipation and suggests a novel principle in the self-organization of systems far from equilibrium. A similar principle may apply to active matter, which is another important class of out-of-equilibrium systems. On noting that interaction forces in active matter, and particularly in living systems, are often non-conservative and dissipative, our finding may also shed new light on the state selection in these systems.