Transition to a labyrinthine phase in a driven granular medium

TL;DR

This paper reports the experimental observation of labyrinthine patterns in a driven granular medium, showing a transition from a granular gas to a labyrinthine phase characterized by chain formation, analyzed through particle tracking and modeling.

Contribution

It provides the first experimental evidence of labyrinthine phases in a macroscopic, out-of-equilibrium granular system, with analysis of transition mechanisms and chain formation.

Findings

Labyrinthine phase observed in macroscopic particles

Transition characterized by interaction strength and agitation ratio

Chains form and are explained by a simple model

Abstract

Labyrinthine patterns arise in two-dimensional physical systems submitted to competing interactions, ranging from the fields of solid-state physics to hydrodynamics. For systems of interacting particles, labyrinthine and stripe phases were studied in the context of colloidal particles confined into a monolayer, both numerically by means of Monte Carlo simulations and experimentally using superparamagnetic particles. Here we report an experimental observation of a labyrinthine phase in an out-of-equilibrium system constituted of macroscopic particles. Once sufficiently magnetized, they organize into short chains of particles in contact and randomly orientated. We characterize the transition from a granular gas state towards a solid labyrinthine phase, as a function of the ratio of the interaction strength to the kinetic agitation. Spatial local structure is analyzed by means of an accurate particle tracking. Moreover, we explain the formation of these chains using a simple model.