Visualizing the interplay of Dirac mass gap and magnetism at nanoscale in intrinsic magnetic topological insulators
Abstract
In intrinsic magnetic topological insulators, Dirac surface-state gaps are prerequisites for quantum anomalous Hall and axion insulating states. Unambiguous experimental identification of these gaps has proved to be a challenge, however. Here, we use molecular beam epitaxy to grow intrinsic MnBi 2 Te 4 thin films. Using scanning tunneling microscopy/spectroscopy, we directly visualize the Dirac mass gap and its disappearance below and above the magnetic order temperature. We further reveal the interplay of Dirac mass gaps and local magnetic defects. We find that, in high defect regions, the Dirac mass gap collapses. Ab initio and coupled Dirac cone model calculations provide insight into the microscopic origin of the correlation between defect density and spatial gap variations. This work provides unambiguous identification of the Dirac mass gap in MnBi 2 Te 4 and, by revealing the microscopic origin of its gap variation, establishes a material design principle for realizing exotic states in intrinsic magnetic topological insulators.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 10, 2022
- Source ID
- 10.1073/pnas.2207681119
Entities
People
- Allan H. MacDonald
- Chao Lei
- Chih-Kang Shih
- Hyunsue Kim
- Jiaqiang Yan
- Lisa Frammolino
- Mengke Liu
- Yanxing Li
Organizations
- Air Force Office of Scientific Research
- National Science Foundation
- Oak Ridge National Laboratory
- University of Texas at Austin