APS -APS March Meeting 2017 - Event - Vanadium impurity state in the doped Sb$_{2}$Te$_{3}$ quantum anomalous Hall system

摘要

The quantum anomalous Hall (QAH) effect has recently been reported in the ferromagnetic topological insulator V-doped (Sb,Bi)$_{2}$Te$_{3}$. However, the microscopic origin of the insulating ferromagnetic ground state is unclear. We employed scanning tunnelling microscopy and spectroscopy on (Sb$_{1-x}$V$_{x}$)$_{2}$Te$_{3}$, and identified two types of V substitutions, in the first and second Sb layers beneath the surface. We found that, second-layer V substitutions? induce a peak within the bulk gap, which may form an impurity band at high impurity concentration. However, first-layer V substitutions suppress the impurity state and locally induce a gap in the surface state. Our results clarified the contribution of the V impurity state to the electronic structure of this QAH system.