Phase coexistence implications of violating Newton's third law

Area of Science:

• Statistical Mechanics
• Soft Matter Physics
• Computational Materials Science

Background:

• Newton's third law (action = reaction) is fundamental to classical mechanics.
• Living and natural systems often exhibit nonreciprocal interactions, seemingly violating this law.
• Understanding these violations is key to explaining biological structures and designing novel materials.

Purpose of the Study:

• To investigate the macroscopic phase behavior resulting from broken microscopic interaction reciprocity.
• To explore how varying degrees of nonreciprocity influence a model system's structure.
• To map the phase diagram and characterize emergent phases in nonreciprocal systems.

Main Methods:

• Utilized computer simulations to model a binary mixture of attractive particles.
• Introduced a continuous parameter to quantify the degree of broken interaction reciprocity.
• Mapped the complete phase diagram and analyzed the characteristics of various phases.

Main Results:

• In the reciprocal limit, the system exhibits phase separation into domains with distinct densities and identical compositions.
• Increasing nonreciprocity leads to diverse phases, including those with composition asymmetry and three-phase coexistence.
• Observed novel states like traveling crystals and liquids, which lack equilibrium analogs.

Conclusions:

• Nonreciprocal interactions drive systems to explore a rich variety of non-equilibrium phases.
• The findings provide a framework for understanding how nonreciprocity shapes structures in living systems.
• This research offers potential pathways for designing advanced synthetic materials with tunable properties.