Topological aspect of Kondo insulator

The experimental observations of the in-gap state by various measurements on a Kondo insulator provide a special and interesting character on the insulator. We show that the system is classified into the strong topological insulator leading to the topologically protected surface states within the gap on the surface and the in-gap states correspond to the surface states of the topological insulator. We argue the spectral functions and spin textures for different surfaces, comparing with recent angle resolved photoemission data. We also discuss the necessity of more sophisticated calculation in order to understand the whole picture of this compound.