Universal gapless Dirac cone and tunable topological states in (MnBi2Te4)m(Bi2Te3)n heterostructures

The newly discovered magnetic topological insulators (MnBi2Te4)(m)(Bi2Te3)(n) are predicted to be a versatile platform for exploring novel topological states. Here, we report angle-resolved photoemission spectroscopy studies on a series of (MnBi2Te4)(m)(Bi2Te3)(n) heterostructures. An unexpected but universal gapless Dirac cone is observed on the (MnBi2Te4) terminated (0001) surfaces in all systems, indicating an altered magnetic structure near the surface. The specific band dispersion of the surface states, presumably dominated by the top surface, is found to be sensitive to different stackings of the underlying MnBi2Te4 and Bi2Te3 layers. Our results suggest the high tunability of both magnetic and electronic structures of the topological surface states in (MnBi2Te4)(m)(Bi2Te3)(n) heterostructures, which is essential in realizing and manipulating various topological states.