  We theoretically investigate dynamic structure factors of a strongly
interacting Fermi superfluid near an orbital Feshbach resonance with random
phase approximation, and find their dynamical characters during the phase
transition between a balanced conventional Bardeen-Cooper-Schrieffer superfluid
and a polarized Sarma superfluid by continuously varying the chemical potential
difference of two spin components. In a BEC-like regime of the BCS superfluid,
dynamic structure factors can do help to distinguish the in-phase ground state
from the out-of-phase metastable state by the relative location of molecular
excitation and Leggett mode, or the minimum energy to break a Cooper pair. In
the phase transition between BCS and Sarma superfluid, we find the dynamic
structure factor of Sarma superfluid has its own specific gapless excitation at
a small transferred momentum which is mixed with the collective phonon
excitation, and also a relatively strong atomic excitation at a large
transferred momentum because of the existence of unpaired Fermi atoms, these
signals can be used to differentiate Sarma superfluid from BCS superfluid.
