  Cold atoms experiments offer invaluable information on superfluid dynamics,
including decay cascades of topological defects. While the cascade properties
are well established for Bose systems, our understanding of their behavior in
Fermi counterparts is very limited, in particular in spin-imbalanced systems,
where superfluid (paired) and normal (unpaired) particles naturally coexist
giving rise to complex spatial structure of the atomic cloud. Here we show,
based on a newly developed microscopic approach, that the decay cascades of
topological defects are dramatically modified by the spin-polarization. We
demonstrate that decay cascades end up at different stages: "dark soliton",
"vortex ring" or "vortex line", depending on the polarization. We reveal that
it is caused by sucking of unpaired particles into the soliton's internal
structure. As a consequence vortex reconnections are hindered and we anticipate
that quantum turbulence phenomenon can be significantly affected, indicating
new physics induced by polarization effects.
