Gapless Dirac surface states in the antiferromagnetic topological insulator MnBi2 Te4

Swatek, Przemyslaw; Wu, Yun; Wang, Lin-Lin; Lee, Kyungchan; Schrunk, Benjamin; Yan, Jiaqiang; Kaminski, Adam

Gapless Dirac surface states in the antiferromagnetic topological insulator MnBi2 Te4

File

IS_J_9990.pdf (1.36 MB)

Date

2020-04-15

Authors

Swatek, Przemyslaw

Wu, Yun

Wang, Lin-Lin

Lee, Kyungchan

Schrunk, Benjamin

Yan, Jiaqiang

Kaminski, Adam

Organizational Units

Organizational Unit

Ames National Laboratory

Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.

For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.

Organizational Unit

Physics and Astronomy

Physics and astronomy are basic natural sciences which attempt to describe and provide an understanding of both our world and our universe. Physics serves as the underpinning of many different disciplines including the other natural sciences and technological areas.

Department

Ames National LaboratoryPhysics and Astronomy

Abstract

We used angle-resolved photoemission spectroscopy (ARPES) and density functional theory calculations to study the electronic properties of MnBi2Te4, a material that was predicted to be an intrinsic antiferromagnetic (AFM) topological insulator. In striking contrast to earlier literature showing a full gap opening between two surface band manifolds on the (0001) surface, we observed a gapless Dirac surface state with a Dirac point sitting at EB=−280meV. Furthermore, our ARPES data revealed the existence of a second Dirac cone sitting closer to the Fermi level. Surprisingly, these surface states remain intact across the AFM transition. The presence of gapless Dirac states in this material may be caused by different ordering at the surface from the bulk or weaker magnetic coupling between the bulk and surface. Whereas the surface Dirac cones seem to be remarkably insensitive to the AFM ordering most likely due to weak coupling to magnetism, we did observe a splitting of the bulk band accompanying the AFM transition. With a moderately high ordering temperature and interesting gapless Dirac surface states, MnBi2Te4 provides a unique platform for studying the interplay between magnetic ordering and topology.