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Chinese Academy of Sciences scientists make progress in the study of magnetic topological semi-metal materials

  The team of scientists from the Chinese Academy of Sciences, researcher Zhang Changjin and the research team of the Strong Magnetic Field Science Center of the Hefei Institute of Material Science, have made new progress in the study of magnetic topological semi-metal materials. The researchers conducted in-depth studies on the magnetic systems of lanthanide metal lanthanides such as NdSb and DySb through magnetic, transport measurements and first-principles calculations under strong magnetic fields, and found magnetic topological semi-metallic states.


  Topological semi-metal is a new class of topological materials with low-energy excited states similar to elementary particles, which is of great significance in scientific cognition and practical application. Among them, Dirac's semi-metal Dirac point has both crystal symmetry and time-reversal symmetry, and is called "three-dimensional graphene". If the crystal symmetry or time inversion symmetry breaks, the Dirac point becomes a foreign point and forms a foreign semi-metal. The foreign semi-metals with crystal symmetry breaking have been found in TaAs, WTe2 and other systems, while the time-reversed symmetry-broken foreign semi-metals have not been discovered for a long time. The main reason is that the angular resolution photoelectron spectroscopy has great limitations in the study of magnetic materials, and cannot provide a clear electronic structure in the magnetic ordered state. Theoretically predicting systems that may have magnetic topological semimetal states include lanthanide metal tellurides, tellurides, and GdPtBi, Mn3Sn, and the like.


  In this work, the researchers used magnetic and transport measurements under strong magnetic fields to study the magnetic structure transitions of NdSb, DySb and other materials, and analyzed the basic information and carrier characteristics of electron transport under different magnetic structures. The principle of energy can be calculated. It is found that the antiferromagnetic state of NdSb is a semi-metallic state of Dirac, and the ferromagnetic state of DySb is a semi-metallic state of the outer phase. In particular, the negative magnetoresistance caused by the chiral anomalies observed on NdSb provides solid evidence for the existence of topological semi-metallic states. NdSb and DySb also provide an ideal carrier for studying the relationship between magnetism and topology with its tunable magnetic structure.


  The transport measurements for this series of work were performed on the No. 1 water-cooled magnet WM1 and the hybrid magnet of the steady-state strong magnetic field experimental setup. The magnetic measurements were made on the magnetic measurement system (VSM) of the No. 2 water-cooled magnet WM2.


  The work was supported by the National Key R&D Program and the National Natural Science Foundation. The main completions were artificial graduates Wang Yongjian and Liang Dandan. Relevant research was published in Physical Review B and APL Materials.

  NdSb high field susceptibility, magnetoresistance measurement (top) and negative reluctance measurement (below) (WM2 on the upper left provides the highest field 25T, and WM1 on the upper right provides the highest field 38T)

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