Heterostructures

Interfacing ferromagnetic insulators with 3D topological insulators offers the potential to engineer heterostructures that can host the Quantum Anomalous Hall (QAH) insulator and Topological Magnetoelectric effect phases. These phases are realised as a result of magnetisation that breaks time reversal symmetry and opens up an exchange gap. Single septuple layer (SL) of MnBi₂Te₄ (MBT) has recently been reported to be a 2D ferromagnetic insulator possessing a bandgap >700 meV with long-range ferromagnetic order.¹ Its chemical and structural similarity to the 3D topological insulator Bi₂Te₃, has led to predictions that MBT/BT/MBT heterostructures may yield robust QAH insulator phases with bandgaps >50 meV.² Here we demonstrate the growth of 1SL MnBi₂Te₄ and 4QL Bi₂Te₃ heterostructures via MBE, and probe the electronic structure using angle resolved photoelectron spectroscopy. We observe massive Dirac Fermions with band gaps >50meV and strong hexagonal warping of the Dirac cone, in excellent agreement with theory. The engineering of massive Dirac Fermions and the QAH insulator phase in MBT/BT/MBT heterostructures has potential applications in spintronics and quantum computing.
¹ Trang et al., arXiv:2009.06175
² Otrokov et al., 2D Mater. 4, 025082 (2017)