  We propose a new protocol to examine many-polaron properties in a cold atom
experiment. Initially, polaronic clouds are prepared around the opposite edges
of a majority gas cloud. After time evolution, the collision of two clouds
exhibits various polaronic effects. To see how {\it collective} properties of
many polarons with mediated interactions appear in the case in which the
impurity and majority gases are composed of mass-balanced fermions with
different spin components, we perform a nonlinear hydrodynamic simulation for
collisional dynamics of two Fermi polaronic clouds. We found that the dynamics
is governed by the impurity Fermi pressure, polaron energy, and multi-polaron
correlations. In particular, shock waves occur in such a way as to reflect the
many-body properties of polarons through the first sound of minority clouds.
Our idea is applicable to other systems such as Bose polarons as well as
mass-imbalanced mixtures.
