Bulk and microphase separation in chiral active systems

Abstract

Many active particles phase-separate due to quorum-sensing interactions, and their self-propulsion mechanisms often break chiral symmetry. Using particle and continuum models, we uncover the role of chirality in inducing bulk or microphase separation, including a chiral phase formed of vapor bubbles. Analytical predictions for the emergence of these phases require a coarse-graining technique based on multiple-scale analysis. Further, introducing a minimal active field theory, we show that, in the bulk phase separation regime, chirality does not alter the diffusive $t^{1/3}$ coarsening law nor the dynamical exponent associated with capillary waves, but induces traveling waves at the interface. We finally demonstrate that, even in the absence of fluid flows, chirality can cause the breakup of elongated droplets, resembling phenomena previously observed experimentally.