Two-dimensional melting far from equilibrium in a granular monolayer

TL;DR

This study experimentally explores the phase transition from solid to liquid in a vibrated granular monolayer, revealing a dislocation-mediated continuous melting process similar to equilibrium hard disk systems, despite being far from equilibrium.

Contribution

It demonstrates that granular monolayers exhibit a continuous melting transition mediated by dislocations, akin to equilibrium systems, even under far-from-equilibrium conditions.

Findings

Dislocation density increases at transition point

Correlation functions indicate a continuous phase transition

Similarity to equilibrium hard disk melting observed

Abstract

We report an experimental investigation of the transition from a hexagonally ordered solid phase to a disordered liquid in a monolayer of vibrated spheres. The transition occurs as the intensity of the vibration amplitude is increased. Measurements of the density of dislocations and the positional and orientational correlation functions show evidence for a dislocation-mediated continuous transition from a solid phase with long-range order to a liquid with only short-range order. The results show a strong similarity to simulations of melting of hard disks in equilibrium, despite the fact that the granular monolayer is far from equilibrium due to the effects of interparticle dissipation and the vibrational forcing.