Magnetic Quincke rollers with tunable single-particle dynamics and collective states.

Electrohydrodynamically driven active particles based on Quincke rotation have quickly become an important model system for emergent collective behavior in nonequilibrium colloidal systems. Like most active particles, Quincke rollers are intrinsically nonmagnetic, preventing the use of magnetic fields to control their complex dynamics on the fly. Here, we report on magnetic Quincke rollers based on silica particles doped with superparamagnetic iron oxide nanoparticles.

Diversity of non-equilibrium patterns and emergence of activity in confined electrohydrodynamically driven liquids.

Spontaneous emergence of organized states in materials driven by non-equilibrium conditions is of notable fundamental and technological interest. In many cases, the states are complex, and their emergence is challenging to predict. Here, we show that an unexpectedly diverse collection of dissipative organized states emerges in a simple system of two liquids under planar confinement when driven by electrohydrodynamic shearing.

Clustering and anisotropic correlated percolation in polar flocks.

We study clustering and percolation phenomena in the Vicsek model, taken here in its capacity of prototypical model for dry aligning active matter. Our results show that the order-disorder transition is not related in any way to a percolation transition, contrary to some earlier claims. We study geometric percolation in each of the phases at play, but we mostly focus on the ordered Toner-Tu phase, where we find that the long-range correlations of density fluctuations give rise to an anisotropic percolation transition.

Chaotic behavior of three interacting vortices in a confined Bose-Einstein condensate.

Motivated by recent experimental works, we investigate a system of vortex dynamics in an atomic Bose-Einstein condensate (BEC), consisting of three vortices, two of which have the same charge. These vortices are modeled as a system of point particles which possesses a Hamiltonian structure. This tripole system constitutes a prototypical model of vortices in BECs exhibiting chaos.