Abstract
The interplay between magnetism and nontrivial topology in magnetic topological insulators (MTIs) is expected to give rise to exotic topological quantum phenomena like the quantum anomalous Hall effect and the topological axion states. A key to assessing these novel properties is to realize gapped topological surface sates. MnBi2Te4 possesses nontrivial band topology with an intrinsic antiferromagnetic state. However, the highly electron-doped nature of the MnBi2Te4 crystals obstructs the exhibition of the surface band gap. Here, we tailor the material through Sb substitution to reveal the gapped surface states in MnBi2-xSbxTe4. By shifting the Fermi level into the bulk band gap, we access the surface states and show a band gap of 50 meV at the Dirac point from quasiparticle interference measured by scanning tunneling microscopy (STM). Surface-dominant conduction is confirmed through transport spectroscopy measured by multiprobe STM below the Néel temperature. The surface band gap is robust against the out-of-plane magnetic field despite the promotion of field-induced ferromagnetism. The realization of bulk-insulating MTIs with the large exchange gap offers a promising platform for exploring emergent topological phenomena.
| Original language | English |
|---|---|
| Article number | 115402 |
| Journal | Physical Review B |
| Volume | 102 |
| Issue number | 11 |
| DOIs | |
| State | Published - Sep 2020 |
Funding
This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The research by J.Y. and S.O. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. A.D.P. was financially supported by the Oak Ridge National Laboratory's Laboratory Directed Research and Development project (Project ID 7448, PI: P.G.). Part of the research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. F.L. acknowledges funding from the Alexander von Humboldt foundation through a Feodor Lynen postdoctoral fellowship. We acknowledge the assistance of J. Burns and J. Poplawsky for focused ion beam milling of the STM tips.
| Funders | Funder number |
|---|---|
| Oak Ridge National Laboratory | ID 7448 |
| U.S. Department of Energy | DE-AC02-05CH11231 |
| Alexander von Humboldt-Stiftung | |
| Office of Science | |
| Basic Energy Sciences | |
| Division of Materials Sciences and Engineering |