Dynamics of a chiral active grain

Externally driven granular matter constitutes a useful system for studying the physics of active matter. Usually, self-propulsion is induced in individual grains by incorporating a suitable asymmetry in shape or some dynamical aspect, such as the frictional interaction. In this work, we introduce a simple model of grain, where the chiral activity emerges through a sequence of spontaneous symmetry breaking in the particle’s kinetics. As a result, the system shows a distinct statistical response, including a non-Gaussian velocity distribution with multiple peaks, a broad power-law curvature distribution, and a bounded chirality probability along with a phase transition from passive achiral to active chiral state as a function of vibration amplitude. Our study establishes this as a model experimental system to study the non-equilibrium statistical mechanics of chiral active systems and can inspire novel locomotion strategies in robotics.