Work

Nonreciprocity as a Generic Mechanism for Demixing in Flocking Mixtures

Year: 2026

Type: article

Abstract: We show that even weak nonreciprocal alignment leads to large-scale structure formation in flocking mixtures. By combining numerical simulations of a binary Vicsek model and the analysis of coarse-grained continuum equations, we demonstrate that nonreciprocity destabilizes the ordered phase formed by mutually aligning or antialigning species in a large part of the phase diagram. For aligning populations, this instability results in one species condensing in a single band that travels within a homogeneous liquid of the other species. When interactions are antialigning, both species self-assemble into polar clusters with large-scale chaotic dynamics. In both cases, the emergence of structures is accompanied by the demixing of the two species, despite the absence of repulsive interactions. Our theoretical analysis allows us to elucidate the origin of the instability, and show that it is generic to nonreciprocal flocks.

Source: Physical Review Letters

DOI: 10.1103/v435-qnhl

Authors: Charlotte Myin, Benoît Mahault

Institution: Max Planck Institute for Dynamics and Self-Organization

Language: English

Topic: Micro and Nano Robotics

Subfield: Condensed Matter Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,750

Funders: International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, International Max Planck Research School for Advanced Methods in Process and Systems Engineering