In this talk, I will show kagome electronic bands in post-annealed MoTe₂ monolayers. A coloring-triangle (CT) latticed MoTe₂ monolayer [1], termed CT-MoTe₂, was constructed by controllably introducing uniform and ordered mirror-twin-boundaries into a pristine monolayer. This CT-MoTe₂ monolayer has an electronic Janus lattice, i.e., an energy-dependent atomic-lattice and a pseudo-Te sublattice, and shares the identical geometry with the Mo₅Te₈ layer. Dirac-like and flat electronic bands inherently existing in the CT lattice are identified by two broad and two prominent peaks in STS spectra, respectively, and verified with DFT calculations. Further explore this category of post-annealed MoTe₂ monolayers, we found another defective monolayer [2], namely Mo₃₃Te₅₆, which is the most stable monolayer in a certain range of the chemical potential of Te. This monolayer contains two sets of kagome bands across the Fermi level, while the nominal flat band of one of the two sets shows a corelated gap with inequivalent responses to external magnetic fields. We next present a “surface” kagome states found on the Sn terminated surface of Co₃Sn₂S₂, although atoms of the surface are arranged in a triangular lattice [3]. Finally, I will demonstrate the constriction of an antiferromagnetic single-atomic chain, namely CrCl₃, using a specially selected substrate and well controlled chemical potentials of the Cl vapor [4]. If I still have time, I will comment on the validity of the type-II multiferroicity in the NiI₂ monolayer [5].
 

[1] L. Lei, et. al. arXiv:2302.06166 (2023).
[2] Z. Pan, et. al. arXiv: 2307.06001 (2023). 
[3] L. Huang, et. al. arXiv:2305.00826 (2023).
[4] S. Lu, et. al. Nature Communications 14, 2465 (2023)
[5] N. Liu, et al. arXiv: 2211.14423v3 (2023)
 

Ji, Wei (季威) is a computational physicist, working in the field of surface and interface modelling of low-dimensional materials. His recent research interests include theoretical modelling of electronic, magnetic and optical properties, as well as growth and exfoliation of two-dimensional materials. He received his Ph.D in condensed matter physics from the Institute of Physics, Chinese Academy of Science in 2008. Prior to joining Renmin University of China, he spent four years in McGill University as a visiting scholar and then a postdoctoral fellow. He was originally appointed as an Associate Professor by Renmin University in 2010 and was early promoted to Full Professor in 2014. He was supported by or awarded with four national innovative projects or professorships in 2014, 2015, 2016 and 2021. He also serves as an Associated Editor of ACS Applied Electronic Materials, an Editorial Board Member of Science Bulletin, Chinese Physics B, Frontiers of Physics and 2D Materials, as well as a committee member of the computational materials science division of the Chinese Materials Research Society. He published over 200 papers in scientific journals like Science, Nature Materials, and Nature Nanotechnology, which have received over 13,000 citations (WoS).

Please contact phweb@ust.hk should you have questions about the talk.