  We numerically investigate the self-diffusion coefficient and correlation
length of the rigid clusters (i.e., the typical size of the collective motions)
in sheared soft athermal particles. Here we find that the rheological flow
curves on the self-diffusion coefficient are collapsed by the proximity to the
jamming transition density. This feature is in common with the well-established
critical scaling of flow curves on shear stress or viscosity. We furthermore
reveal that the divergence of the correlation length governs the critical
behavior of the diffusion coefficient, where the diffusion coefficient is
proportional to the correlation length and the strain rate for a wide range of
the strain rate and packing fraction across the jamming transition density.
