  We theoretically study the electric current induced by the temporally
oscillating magnetic field onto a three-dimensional topological insulator based
on the linear response theory. The electric current flows on its surface
because of the unique characters of the surface states: the linear dispersion
in two-dimension and the chiral spin texture on the Fermi surface. In the bulk
region, on the other hand, the current is absent because of the degeneracy for
the bulk bands. The response function has a peak structure when the frequency
of the magnetic field is equal to twice of the Fermi energy of the surface
states measured from the Dirac node. This feature is unique to the surface
states on the three-dimensional topological insulator.
