Nonreciprocity-induced crystallization and melting

Crystallization and the melting of crystals are two fundamental processes in statistical physics. At thermal equilibrium, such processes can be understood using a simple yet generic picture of free energy minimization. This picture, however, is usually not applicable to systems away from equilibrium. Here, we study a binary particle system with nonreciprocal inter-species interaction, and find that nonreciprocity can give rise to spontaneous crystallization and melting of particles whose mechanisms are fundamentally different from those of their equilibrium counterparts. We develop a theory to explain the nonreciprocity-induced crystallization and melting, highlighting the dynamic nature of these processes.