  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.
