  We investigate the time evolution of a Fermi-Hubbard model with long range
hopping following a sudden quench of the local interactions among different
spin species. The quasi-particle spectrum consists of gapped low-energy levels
while the high energy modes accumulate at a single point. When the low energy
gaps are large enough, turning on the local interactions does not effectively
mix high and low energy modes, leading to the freezing of the dynamical
evolution. In general, the states within the excited subspace are shielded from
the long-range signatures of the model, which are responsible for the low
energy extended states, and the dynamics effectively look as if long-range
hopping were absent. This cooperative shielding mechanism becomes evident in
presence of disorder. It is shown that shielding and freezing are a universal
feature of long-range interacting systems and conjecture that they are related
to the existence of quasi-stationary states.
