Abstract:
Labyrinthine patterns
arise in two-dimensional physical systems submitted to competing
interactions, in fields ranging from 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. The spatial local structure is analyzed by
means of accurate particle tracking. Moreover, we explain the
formation of these chains using a simple model.