  Shortly after the discovery of topological band insulators, the topological
Kondo insulators (TKIs) have also been theoretically predicted. The latter has
ignited revival interest in the properties of Kondo insulators. Currently, the
feasibility of topological nature in SmB$_6$ has been intensively analyzed by
several complementary probes. Here by starting with a minimal-orbital Anderson
lattice model, we explore the local electronic structure in a Kondo insulator.
We show that the two strong topological regimes sandwiching the weak
topological regime give rise to a single Dirac cone, which is located near the
center or corner of the surface Brillouin zone. We further find that, when a
single impurity is placed on the surface, low-energy resonance states are
induced in the weak scattering limit for the strong TKI regimes and the
resonance level moves monotonically across the hybridization gap with the
strength of impurity scattering potential; while low energy states can only be
induced in the unitary scattering limit for the weak TKI regime, where the
resonance level moves universally toward the center of the hybridization gap.
These impurity induced low-energy quasiparticles will lead to characteristic
signatures in scanning tunneling microscopy/spectroscopy, which has recently
found success in probing into exotic properties in heavy fermion systems.
