Polydispersity enhances the dynamics of Active Brownian particles.

We study the dynamics and the phases of self-propelled disk-shaped particles of different sizes with soft repulsive potential in two dimensions. We observe enhanced dynamics for large size diversity among the particles. Size diversity is defined by the polydispersity index $\epsilon$, which is the width of the uniform distribution of the particle's radius. We calculate the steady-state diffusion coefficient $D_{eff}$ and for high self-propulsion speed $v_0$, it follows a scaling function $D_{eff} \sim D_0 \bar{v}_0^{\beta} f(\epsilon \bar{v}_0^{-\alpha})$, where $\alpha$ and $\beta$ are the two exponents and independent of the self-propulsion speed and the polydispersity index. The phase diagram exhibits a liquid phase with a large number-fluctuations for high self-propulsion speed $v_0$ and a jammed phase at low $v_0$ with small number fluctuation. Further, we categorize the phases into solid-jammed and MIPS-liquid for low polydispersity ($\epsilon$) where the particles form periodic clusters. In contrast, we call it liquid-jammed and liquid phase for high $\epsilon$ where particles form non-periodic clusters. We study the system for three different packing densities of the particles, and the system responds in the same fashion for the polydispersity in the particles' size. Our study can help understand the behavior of cells of various sizes in a tissue, artificial self-driven granular particles, or living organisms of different sizes in a dense environment.