Emergent mixing or de-mixing in heterogeneous colloidal flocks

Abstract

This work explores how individual variability or heterogeneity shapes collective motion in active matter, using a synthetic active system comprising a binary flock of Quincke rollers. These flocks generate spontaneous global demixing within polar vortices or exhibit suppressed global demixing, where polar and anisotropic order persists at local scales. We also develop a multicomponent hydrodynamic model that captures the emergent sorting arising from the interplay between differences in self-propulsion speed and non-reciprocal repulsive interactions. Thus, we elucidate how activity disparity, non-reciprocal interactions, and confinement geometry collectively govern spatial self-organization in active systems, providing broader insight into how individual heterogeneity can drive emergent collective behavior.