Ab initio identification of two-dimensional square-octagonal bismuthene doped with 3d transition metals as potential spin gapless semiconductor, bipolar magnetic semiconductor, and quantum anomalous Hall insulator

The electronic structures and magnetic properties of square-octagonal bismuthene embedded with 3d transition elements were studied systematically by the first-principles calculations. The formation energies of all the cases are negative, indicating the feasibility and practicability for these doped monolayer bismuthene. No considerable spin splitting appears in Sc-, Co-, and Zn-doped compounds. After doping, Scand Co-doped compounds are semiconductors while Zn-doped compound is metal. Ti-, V-, Cr-, Mn-, Fe-, Ni-, and Cu-doped systems behave as magnetic semiconductors. Among them, Cu-doped system exhibits both desirable spin gapless and bipolar magnetic semiconducting characteristics. In addition, Fe-doped system is a wonderful candidate for realizing quantum anomalous Hall insulating state.