Phase Separation, Capillarity, and Odd Surface Flows in Chiral Active Matter

TL;DR

This paper develops a theory for phase separation and interfacial phenomena in chiral active matter, revealing how chirality influences phase coexistence, interfacial flows, and stability, supported by Brownian dynamics simulations.

Contribution

It introduces a non-equilibrium theoretical framework for chiral active matter, accounting for parity violation and odd surface flows, expanding understanding beyond symmetric systems.

Findings

Chirality suppresses phase separation.

Steady-state tangential currents develop at interfaces.

Capillary surface tension governs interfacial stability and fluctuations.

Abstract

Active phase separations evade canonical thermodynamic descriptions and have thus challenged our understanding of coexistence and interfacial phenomena. Considerable progress has been made towards a non-equilibrium theoretical description of these traditionally thermodynamic concepts. Spatial parity symmetry is conspicuously assumed in much of this progress, despite the ubiquity of chirality in experimentally realized systems. In this Letter, we derive a theory for the phase coexistence and interfacial fluctuations of a system which microscopically violates spatial parity. We find suppression of the phase separation as chirality is increased as well as the development of steady-state currents tangential to the interface dividing the phases. These odd flows are irrelevant to stationary interfacial properties, with stability, capillary fluctuations, and surface area minimization determined entirely by the capillary surface tension. Using large-scale Brownian dynamics simulations, we find excellent agreement with our theoretical scaling predictions.