Optimization of the intrinsic magnetic topological insulator MnBi₂Te₄ and transport study

Magnetic topological insulators (MTIs) offer a combination of topologically nontrivial characteristics and magnetic order and show promise in terms of potentially interesting physical phenomena such as quantum anomalous Hall (QAH) effect. However, the understanding of their properties and potential applications have been limited due to a lack of suitable MTIs. Here, we grow single crystals of Mn(Sb,Bi)₂Te₄ to search for intrinsic MTIs. We perform angle-resolved photoemission spectroscopy, transport measurements, and first-principles calculations to investigate the band structure, transport properties, and magnetism, as well as the evolution of their topological properties. We find that there exists an optimized MTI zone in the Mn(Sb,Bi)₂Te₄ phase diagram, which could possibly host a high-temperature QAH phase. We also report the reserved anomalous Hall effect (AHE) in the MnBi₂Te₄ thin film. By employing the top/bottom gate, a negative AHE loop gradually decreases to zero and changes to a reversed sign. The reversed AHE exhibits distinct coercive fields and temperature dependence from the previous AHE. It reaches the maximum inside the gap of the Dirac cone. The reversed AHE is attributed to the competition of intrinsic Berry curvature and extrinsic skew scattering.