Emergent complex phases in a discrete flocking model with reciprocal and non-reciprocal interactions

Abstract

There is growing interest in multi-species active matter systems with reciprocal and non-reciprocal interactions. While such interactions have been explored in continuous symmetry models, less is known about multi-species discrete-symmetry systems. To address this, we study the two-species active Ising model (TSAIM), a discrete counterpart of the two-species Vicsek model. Our investigation explores both inter-species reciprocal and non-reciprocal interactions, along with the possibility of species interconversion. In the reciprocal TSAIM, we observe the emergence of a high-density parallel flocking state, a feature not seen in previous flocking models. With species interconversion, the TSAIM corresponds to an active extension of the Ashkin-Teller model and exhibits rich state diagrams. In the non-reciprocal TSAIM, a run-and-chase dynamics emerge. We also find that the system is metastable due to droplet excitation and exhibits spontaneous motility-induced interface pinning. A hydrodynamic theory validates our numerical simulations and confirms the phase diagrams.

30 pages, 17 figures

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Cited by in corpus (6)

• Stability of flocking in the reciprocal two-species Vicsek model: Effects of relative population, motility, and noise
• Flocking with random non-reciprocal interactions
• Stochastic Thermodynamics of Non-reciprocally Interacting Particles and Fields
• Stability of discrete-symmetry flocks: sandwich state, traveling domains and motility-induced pinning
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• Field-controlled interfacial transport and pinning in an active spin system