Emergence of Rotating Flocks in Active Chiral Liquids

 Active matter plays a key role in studying the emergence of self-assembling and the role of interactions in both synthetic and biological systems. By introducing chirality to a system, multiple layers of complexity become available, that have an impact on the behavior at the individual and collective scale, giving access to new dynamics that are not present without chirality.

Quicke rollers self-propel in a random direction due to spontaneous symmetry breaking, when an electric field is applied perpendicular to the plane the particles move in. We introduce chirality to this system by choosing shape-anisotropic particles that roll on curved paths with activity-controlled radius of curvature and randomly chosen handedness. This leads to new collective phenomena, not available for achiral Quincke rollers. We observe phase separation and spontaneous synchronization of the particles, leading to vortices and rotating flocks. Rotating flocks are currently unique to chiral active systems.

We investigate the nontrivial dynamics of these rotating flocks, the correlation of collective phases between different flocks and their temporal evolution.