  A quantized version of the magnetoelectric effect, known as the topological
magnetoelectric effect, can exist in a time-reversal invariant topological
insulator with all its surface states gapped out by magnetism. This topological
phase, called the axion insulator phase, has been theoretically proposed but is
still lack of conclusive experimental evidence due to the small signal of
topological magnetoelectric effect. In this work, we propose that the dynamical
in-plane magnetization in an axion insulator can generate a "pseudo-electric
field", which acts on the surface state of topological insulator films and
leads to the non-zero response current. Strikingly, we find that the current at
magnetic resonance (either ferromagnetic or anti-ferromagnetic) is larger than
that of topological magnetoelectric effect by several orders of magnitude, and
thereby serves as a feasible smoking gun to confirm the axion insulator phase
in the candidate materials.
