Kinetics of phase transition in nonreciprocal mixtures of passive and chemophoretically active particles.

Abstract

We study phase separation kinetics in two-dimensional binary mixtures of active and passive colloids. An active particle acts as a source of the chemical gradient to induce phoretic motion among the passive particles. Mediated by this effective interaction, the suspension undergoes separation resembling a vapor-liquid phase transition. Via simulations incorporating Langevin dynamics, we construct the related steady-state phase diagram. We exploit this knowledge to study structure and growth associated with kinetics following sudden quenches of homogeneous systems into the miscibility gap, for far-from-critical and near-critical densities. An advanced finite-size scaling technique is employed to calculate the growth exponents in the thermodynamically large system size limit, using data from systems of different finite sizes, for each of the cases. The growth data are described well by a recently constructed analytical function, irrespective of system size and particle density. Our results demonstrate enhancement in the growth exponent when the phoretic strength is increased. For the off-critical case, we have discussed the possible mechanism(s) in the background of an appropriate theoretical picture.