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DY: Fachverband Dynamik und Statistische Physik

DY 31: Particulate Matter I: From microscopic interactions to collective motion (Focus session)

DY 31.8: Vortrag

Mittwoch, 22. März 2017, 12:00–12:15, ZEU 118

Dancing screw nuts: collective behaviour under vertical vibrations — •Simeon Völkel, Manuel Baur, and Kai Huang — Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany

The collective behaviour of vertically vibrated hexagonal disks confined in a horizontal monolayer is investigated experimentally. Unlike spheres or circular disks, hexagonal disks prefer to rotate upon sufficiently strong driving due to the broken circular symmetry. As wetting liquid is added, the rotating disks self-organize into a hexagonal structure, reminiscent of a rotator crystal in equilibrium systems. The bond length of the ordered structure is slightly smaller than the circumdiameter of a hexagon, indicating geometric frustration. At the ``microscopic'' level, we propose an analytical model to predict the rotation speed of individual disks. At the ``macroscopic'' level, we quantify the influence of cohesive particle-particle interactions on the collective behaviour through characterizing the pair correlation and angular distribution functions in the ordered state. Finally we explore the transitions into and out of the rotator crystal state.