  By combining scanning tunneling microscopy/spectroscopy and first-principles
calculations, we systematically study the local electronic states of magnetic
dopants V and Cr in the topological insulator (TI) Sb2Te3. Spectroscopic
imaging shows diverse local defect states between Cr and V, which agree with
our first-principle calculations. The unique spectroscopic features of V and Cr
dopants provide electronic fingerprints for the co-doped magnetic TI samples
with the enhanced quantum anomalous Hall effect. Our results also facilitate
the exploration of the underlying mechanism of the enhanced quantum anomalous
Hall temperature in Cr/V co-doped TIs.
