Abstract
The interplay of nontrivial band topology and magnetism gives rise to a series of exotic quantum phenomena, such as the emergent quantum anomalous Hall (QAH) effect and topological magnetoelectric effect. Many of these quantum phenomena have local manifestations when the global symmetry is broken. Here, we report local signatures of the thickness-dependent topology in intrinsic magnetic topological insulator MnBi2Te4 (MBT), using scanning tunneling microscopy and spectroscopy on molecular beam epitaxy grown MBT thin films. A thickness-dependent band gap is revealed, which we reproduce with theoretical calculations. Our theoretical results indicate a topological quantum phase transition beyond a film thickness of one monolayer, with alternating QAH and axion insulating states for odd and even layers, respectively. At step edges, we observe localized electronic states, in general agreement with axion insulator and QAH edge states, respectively, indicating topological phase transitions across the steps. The demonstration of thickness-dependent topological properties highlights the role of nanoscale control over novel quantum states, reinforcing the necessity of thin film technology in quantum information science applications.
| Original language | English |
|---|---|
| Article number | 035423 |
| Journal | Physical Review B |
| Volume | 105 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jan 15 2022 |
Funding
This research was conducted at the Center for Nanophase Materials Sciences, which is a Department of Energy (DOE) Office of Science User Facility. F.L. acknowledges funding from the Alexander von Humboldt foundation through a Feodor Lynen postdoctoral fellowship. A.D.P.'s initial calculations were financially supported by the Oak Ridge National Laboratory's Laboratory Directed Research and Development project (Project ID No.7448, PI: P.G.). Subsequent computations by A.D.P. were supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as part of the Computational Materials Sciences Program and Center for Predictive Simulation of Functional Materials. The vasp calculations used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. DOE Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. All computations using wannier90 code used resources of the Computer and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. DOE under Contract No. DE-AC05-00OR22725. The development of RMG was funded by the DOE Exascale Computing Project and the National Science Foundation Grant No. OAC-1740309. RMG based computations used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. DOE under Contract No. DE-AC05-00OR22725. The film growth done at Penn State is supported by the Gordon and Betty Moore Foundation's EPiQS Initiative (Grant No. GBMF9063 to C.Z.C.) and ARO Young Investigator Program Award (W911NF1810198). A portion of the research (A.-P.L.) is supported by the U.S. DOE, Office of Science, National Quantum Information Science Research Centers.
| Funders | Funder number |
|---|---|
| CADES | DE-AC05-00OR22725 |
| Data Environment for Science | |
| National Quantum Information Science Research Centers | |
| Oak Ridge National Laboratory | 7448 |
| National Science Foundation | OAC-1740309 |
| U.S. Department of Energy | |
| Army Research Office | W911NF1810198 |
| Gordon and Betty Moore Foundation | GBMF9063 |
| Alexander von Humboldt-Stiftung | |
| Office of Science | DE-AC02-05CH11231 |
| Basic Energy Sciences | |
| Division of Materials Sciences and Engineering |