Realization of tunable gaps in minimal topological electronic structure of MnBi2Te4 via synergistic Sb doping and surface K modification

Topological materials with minimized topological surface states and tunable energy gaps serve as an ideal platform for investigating topological quantum phenomena. In this study, we engineered a minimized topological electronic structure with controllable gaps in the intrinsic magnetic topological insulator MnBi2Te4, through a synergistic strategy combining bulk antimony (Sb) doping and surface potassium (K) modification. Systematic investigations were performed using high-resolution angle-resolved photoemission spectroscopy at 80 K. Bulk Sb doping effectively induces the formation of topological surface state gaps, with their magnitude dramatically increasing from 10 meV in Mn(Bi0.95Sb0.05)2Te4 to 103 meV in Mn(Bi0.76Sb0.24)2Te4, while simultaneously reducing carrier concentration and shifting the Dirac point toward the Fermi level. Subsequent K surface modification induces a non-monotonic Fermi level shift, accompanied by a distinctive “closure-reopening” evolution of the topological surface state gap. We attribute this phenomenon to the transition of surface termination types induced by low-dose K modification and surface potential reconstruction caused by high-dose K deposition. This synergistic doping strategy establishes an effective pathway to achieve the high-temperature quantum anomalous Hall effect.