Non-local Influence of the local ferromagnetic impurities on electronic structure of the topological insulator Cr_0.08(Bi_0.1Sb_0.9)_1.92Te₃

Magnetic impurities break a time-reversal symmetry of topological insulator(TI) and generate a back scattering between the surface states. As a result, a gap opens at the time-reversal invariant momentum and the electronic properties of TI’s undergo a drastic change. We investigated the local density of states(LDOS) of Cr doped TI (Cr_0.08(Bi_0.1Sb_0.9)_1.92Te₃) using the spectroscopic imaging scanning tunneling microscopy(SI-STM) and found that there are two types of impurities: one kind from the 1^st Bi-Sb layer and another kind from the 2^nd Bi-Sb layer. We found that the local Dirac gap magnitude are more correlated to the position of impurities from the 2^nd layer and the quasi-particle interference shows a trace of the back scattering which is prohibited in the undoped TI’s. We will also present a Spectroscopic feature near the Fermi energy and its possible implication.