Edge Currents Shape Condensates in Chiral Active Matter

TL;DR

This paper investigates how edge currents influence the shape and dynamics of condensates in chiral active matter, revealing that active chiral transport leads to polygonal condensate shapes and specific interfacial behaviors.

Contribution

The study introduces a minimal lattice model and a continuum theory to demonstrate the role of active chiral edge currents in shaping condensates in chiral active matter.

Findings

Edge currents induce unidirectional, angle-dependent edge flows.

Condensates form faceted, polygonal shapes with symmetry determined by edge currents.

The continuum model captures the interfacial dynamics and steady-state geometries observed in the lattice model.

Abstract

Chiral active matter, which breaks both parity symmetry and time-reversal symmetry, is ubiquitous in living systems. Here, we introduce a minimal two-dimensional chiral active lattice gas by incorporating stochastic, biased local rotations. At low temperatures, the system coarsens into condensates with chiral orientations and faceted, crystal-like shapes. The interfaces align at characteristic angles with respect to the lattice axes and exhibit edge currents that are persistent, unidirectional, and angle-dependent. To generalise these findings, we propose a continuum theory by adding an active chiral edge current term to Model B, which reveals the essential role of active chiral transport in the interfacial dynamics of phase separation. Edge currents with $n$-fold symmetry produce condensates whose shapes resemble regular $n$-sided polygons. In the thin-interface limit, we construct an effective interface potential governing edge currents, from which the steady-state condensate geometry can be obtained, both in the lattice model and the continuum description.