Massive Dirac fermions and strong Shubnikov-de Haas oscillations in single crystals of the topological insulator Bi2Se3 doped with Sm and Fe

Topological insulators (TIs) are emergent materials with unique band structure, which allow the study of quantum effect in solids, as well as contribute to high-performance quantum devices. To achieve the better performance of TIs, here, we present a codoping strategy using synergistic rare-earth (RE) Sm and transition-metal Fe dopants in Bi2Se3 single crystals, which combine the advantages of both a transition-metal-doped TI [high ferromagnetic ordering temperature and observed quantum anomalous Hall effect (QAHE)], and a RE doped TI (large magnetic moments and significant spin-orbit coupling). In the as-grown single crystals, clear evidences of ferromagnetic ordering were observed. The angle-resolve photoemission spectroscopy indicates the ferromagnetism opens a ∼44 meV band gap at the surface Dirac point. Moreover, the mobility of the carriers at 3 K is ∼7400cm2/Vs, and we thus observed an ultra-strong Shubnikov-de Haas oscillation in the longitudinal resistivity, as well as the Hall steps in transverse resistivity <14 T. Our transport and angular-resolved photoemission spectroscopy results suggest that the RE and transition metal codoping in the Bi2Se3 system is a promising avenue to implement the QAHE, as well as harnessing the massive Dirac fermion in electrical devices.