  Helical edge states of two-dimensional topological insulators show a gap in
the density of states (DOS) and suppressed conductance in the presence of
ordered magnetic impurities. Here we will consider the dynamical effects on the
DOS and transmission when the magnetic impurities are driven periodically.
Using the Floquet formalism and Green's functions, the system properties are
studied as a function of the driving frequency and the potential energy
contribution of the impurities. We see that increasing the potential part
closes the DOS gap for all driving regimes. The transmission gap is also
closed, showing a pronounced asymmetry as a function of energy. These features
indicate that the dynamical transport properties could yield valuable
information about the magnetic impurities.
