Regensburg 2025 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 2: Active Matter I (joint session DY/BP/CPP)
CPP 2.4: Talk
Monday, March 17, 2025, 10:15–10:30, H37
Emergent phases in a discrete flocking model with reciprocal interaction — •Matthieu Mangeat1, Swarnajit Chatterjee1, Jae Dong Noh2, and Heiko Rieger1 — 1Saarland University, Saarbrücken, Germany — 2University of Seoul, Seoul, Korea
We have undertaken a comprehensive study of the two-species active Ising model (TSAIM), a discrete-symmetry counterpart of the continuous-symmetry two-species Vicsek model, motivated by recent interest in the impact of complex and heterogeneous interactions on active matter systems. In the TSAIM, two species of self-propelled particles undergo biased diffusion in two dimensions, interacting via local intraspecies alignment and reciprocal interspecies anti-alignment, along with the possibility of species interconversion. We observe a liquid-gas phase transition, exhibiting macrophase-separated bands, and the emergence of a high-density parallel flocking state, a feature not seen in previous flocking models. With species interconversion (species-flip dynamics), the TSAIM corresponds to an active extension of the Ashkin-Teller model and exhibits a broader range of steady-state phases, including microphase-separated bands that further enrich the coexistence region. We also find that the system is metastable due to droplet excitation and exhibits spontaneous motility-induced interface pinning, preventing the system from reaching long-range order at sufficiently low noise. A hydrodynamic theory complements our computer simulations of the microscopic model and confirms the reported phase diagrams.
Keywords: active matter; flocking; multispecies flocking