Dresden 2017 – wissenschaftliches Programm
CPP 44.1: Vortrag
Mittwoch, 22. März 2017, 15:00–15:15, HÜL 186
Flocking ferromagnetic particles — •Andreas Kaiser, Alexey Snezhko, and Igor S. Aranson — Materials Science Division, Argonne National Laboratory, 9700 South Cass Ave, Argonne, Illinois 60439, USA
Suspensions of microswimmers, show fascinating collective behaviours like clustering, flocking and turbulence . Here, we demonstrate the discovery of ferromagnetic flocking colloids. The self-propulsion is an outcome of the spontaneous rotation of a ferromagnetic colloidal sphere in a vertical alternating (AC) magnetic field . Depending on the frequency of this magnetic field, a sequence of transitions can be observed: from gas-like motion of individual particles to the onset of flocking and global rotation followed by a reentrant flocking and gas-like state for increasing frequency . We also emphasize a subtle role of rotational noise: While the low-frequency flocking appears to be noise-insensitive, the reentrant flocking happens to be noise-activated. Moreover, we uncover a new relation between collective motion and synchronisation.
 T. Vicsek, A. Zafeiris, Physics Reports 517, 71 (2012)
 G. Kokot, D. Piet, G.M. Whitesides, I.S. Aranson, A. Snezkho, Scientific Reports 5, 9528 (2015)
 A. Kaiser, A. Snezkho, I.S. Aranson, Science Advances (submitted)