Wetting and Pattern Formation in Non-Reciprocal Ternary Phase Separation

TL;DR

This paper introduces a minimal ternary phase separation model with non-reciprocal interactions, revealing novel non-equilibrium phenomena such as oscillatory patterns, phase rotation, and traveling waves through simulations and analytical analysis.

Contribution

It presents a new minimal model for non-reciprocal ternary phase separation, extending classical wetting theory to active, non-equilibrium systems.

Findings

Identified three distinct phase behaviors: quasi-static, limit cycle, and traveling wave regimes.

Demonstrated the emergence of oscillatory and directional motion patterns.

Provided analytical insights into stability and wave speed near equilibrium.

Abstract

Non-reciprocal interactions are among the simplest mechanisms that drive a physical system out of thermal equilibrium, leading to novel phenomena such as oscillatory pattern formation. In this paper, we introduce a ternary phase separation model, with non-reciprocal interactions between two of the three phases and a spectator phase that mimics a boundary. Through numerical simulations, we uncover three distinct phase behaviours: a quasi-static regime, characterized by well-defined non-equilibrium contact angles at the three phase contact line; a limit cycle regime, with the three bulk phases rotating around the three phase contact line; and a travelling wave regime, featuring persistent directional motion. We complement our numerical findings with analytical examination of linear stability and the wave propagation speed near equilibrium. Our model provides a minimal framework for extending classical equilibrium wetting theory to active and non-equilibrium systems.