  Population heterogeneity is ubiquitous among active living systems, but
little is known about its role in determining their spatial organization and
large-scale dynamics. Combining evidence from synthetic active fluids assembled
from self-propelled colloidal particles along with theoretical predictions at
the continuum scale, we demonstrate the spontaneous demixing of binary polar
liquids within circular confinement. Our analysis reveals how both active speed
heterogeneity and non-reciprocal repulsive interactions lead to self-sorting
behavior. By establishing general principles for the self-organization of
binary polar liquids, our findings highlight the specificity of multi-component
active systems.
