Transition from a dissipative to a quasi-elastic system of particles with tunable repulsive interactions

S. Merminod, M. Berhanu & E. Falcon
 
Univ Paris Diderot, Sorbonne Cité, MSC, CNRS, UMR 7057, F-75 013 Paris, France, EU

Reference:  EPL 106, 44005 (2014)     Editor's Choice  & Highlight of 2014 from EPL

URL:  http://iopscience.iop.org/0295-5075/106/4/44005/

Abstract:

A two-dimensional system of particles with tunable repulsive interactions is experimentally investigated. Soft ferromagnetic particles are placed on a vibrating rough plate and vertically confined, so that they perform a horizontal Brownian motion in a cell. When immersed in an external vertical magnetic field, the particles become magnetised and thus interact according to a dipolar repulsive law. As the amplitude of the magnetic field is increased, magnetic repulsion raises and the rate of inelastic collisions decreases. Studying the pair correlation function and the particle velocity distributions, we show that the typical properties of such a dissipative out-of-equilibrium granular gas are progressively lost, to approach those expected for a usual gas at thermodynamic equilibrium. For stronger interaction strengths, the system gradually solidifies towards a hexagonal crystal. This new setup could consequently be used as a model experimental system for out-of-equilibrium statistical physics, in which the distance to the quasi-elastic limit can be accurately controlled.


PACS : 45.70.-n   Granular systems
            64.  Equations of state, phase equilibria, and phase transitions
            70.50.-y  Studies of specific magnetic materials


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Supplementary Data:


image1.gif
Movie 1. (4.5 MB M4V) Evolution of the system when the magnetic field is linearly increased. The particle area fraction equals 0.2 and the dimensionless acceleration equals 3.32. (Movie in real time)

Thumbnail, link to movie2.m4v
Movie 2. (2.7 MB M4V) "Dissipative" regime (all parameters fixed). The particle area fraction equals 0.2, the dimensionless acceleration equals 3.32, and the magnetic field is off. (Movie slowed down 30x)

Thumbnail, link to movie3.m4v
Movie 3. (2.7 MB M4V) "Quasi-elastic" regime (all parameters fixed). The particle area fraction equals 0.2, the dimensionless acceleration equals 3.32, and the magnetic field equals 88 G. (Movie slowed down 30x)

Thumbnail, link to movie4.m4v
Movie 4. (2.6 MB M4V) "Crystal" regime (all parameters fixed). The particle area fraction equals 0.2, the dimensionless acceleration equals 3.32, and the magnetic field equals 208 G. (Movie slowed down 30x)


Higher-quality versions of these videos:
Video1.mpg
Video2.mpg
Video3.mpg
Video4.mpg
video2000.mp4


 
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