A Physical Origin for Edge Currents in Chiral Active Liquids

Chiral active matter is a class of non-equilibrium systems where a persistent injection of energy is converted into rotational motion. These systems display exotic hydrodynamic phenomena, such as supporting unidirectional protected edge currents. In this work, we propose a simple physical origin for these edge currents. We study a minimal model of chiral active matter in two dimensions using underdamped Langevin dynamics. Starting from the microscopic equations of motion and invoking the global balance of angular momentum, we derive an Ohmic-like conductance law for the mean current in the dense phase, and we find it to be intensive, depending only on the density, active torque and drag. Moreover, we find the distribution of this current to be Gaussian with a variance that is intensive, depending only on temperature, density and system’s aspect ratio. We validate these results numerically using molecular dynamics simulations in simple geometries. These results provide a new perspective for studying the collective phenomena in active matter through the global balance of conserved quantities.