Kagome Magnet RMn₆Sn₆: First-principles study
Hung-Ju Tien1*, Jia-Xin Yin2, Zi-Jia Cheng2, Tay-Rong Chang1,3, Shuang Jia4, M. Zahid Hasan2,5
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
2Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey, USA
3Center for Quantum Frontiers of Research and Technology (QFort), Taiwan
4International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
5Lawrence Berkeley National Laboratory, Berkeley, CA, USA
* Presenter:Hung-Ju Tien, email:tien12918@gmail.com
Kagome lattice is a two-dimensional honeycomb structure network with triangular corner sharing. Its band structure has been theoretically predicted to possess both flat bands and Dirac states in the Brillouin zone. In addition, the band degeneracy will be lifted and present a topological nontrival gap as considering time-invariant intersite spin-orbit coupling. Recently, a new kagome family RMn₆Sn₆ has been found to provide a tunable magnetic configuration by replacing different rare earth elements R. For example, TbMn₆Sn₆ (R=Tb) shows a ferrimagnetic state with our-of-plane spin orientation. Based on first-principles calculations, we identify a highly orbital-selective massive Dirac state forming by Mn dx²-y²/dxy with 35 meV large energy gap at K point, which is well consistent with our tunneling measurement. Remarkably, our calculation exhibits the strong Berry curvature in this gapped Dirac state, supporting TbMn₆Sn₆ may be an intrinsic Chern insulator. In GdMn6Sn6, our first-principles calculations demonstrate a tunable gap via changing the magnetic configuration. Experimentally, through doping the Tb atoms in GdMn₆Sn₆, the out of plane magnetic configuration can be realized. Our calculation reveals an orbital-selective and a tunable topological gap in kagome magnet RMn6Sn6 and provide a natural platform to investigate the interplay between topology and magnetism.

Keywords: Kagome lattice, Topological materials, First principle calculation