Using the ARPES system at HLS, Profs. Ding Hong and Qian Tian (the Institute of Physics, CAS), Yang Lexian and Chen Yulin (Tsinghua University) have conducted systematic studies on the topological electronic structures in magnetic topological insulator MnBi₂Te₄, and for the first time, topological surface states have been unambiguously observed in a magnetic topological insulator. Prof. Song Fengqi (Nanjing University) substituted Sb for Bi and found that the Fermi level in Mn(Sb_0.3Bi_0.7)₂Te₄ is located in the band gap of the bulk, suggesting this material a platform for device exploration. These studies were published in Physical Review X [9(4):041039(2019); 9(4):041040(2019)] and Nature Communications [10:4469(2019)]. The work published in Physical Review X was selected as Feature in Physics and was reported by Physics of the American Physical Society.

The evolution of band structure with photon energy (Above) ; the effect of Sb doping on the band structure (Below)