Kagome structure originated as an old Asian bamboo basket with both trigonal and hexagonal structures. Recently, the coexistence of charge density wave state and superconductivity has been discovered in a new type of quasi-two-dimensional Kagome system AV₃Sb₅ with the kagome lattice of V atoms. Although the charge density wave and superconductivity have been investigated intensively, the non-trivial electronic band structure have been rarely studied.

Researchers led by Prof. ZHU Xiangde from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences and Prof. LEI Heichang from Renmin University recently studied the quantum transport properties of CsV₃Sb₅ and proved the topological non-mediocre electronic structure in it. Their findings have been published on Physical Review Letters.

The researchers analyzed the quantum oscillation of Shubnikov-de Haas (SdH) and compared them with theoretical calculations from the Stable High Magnetic Field Laboratory of HFIPS.  

Although the superconductivity with Tc = 2.8K (-270.3OC) has been discovered, the predicted nontrivial topological band structures still have not confirmed experimentally. SdH oscillations (which means the resistivity has an oscillation part versus magnetic field) of CsV₃Sb₅ were observed by magnetic resistance measurements up to 35 Tesla at low temperatures, which clearly proved the non-trivial topological band structure of CsV₃Sb₅.  All the experimental results are consistent with the theoretical ones.

These results show that in addition to the reported charge-density waves and superconductivity, the Kagome material CsV₃Sb₅ exhibits a non-trivial topological electronic band structure.  

(a) a traditional Asian bamboo basket; (b) the fine structure of bamboo knitting; (c) The crystal structure of CsV₃Sb₅ viewed from c-axis. (Image by ZHU Xiangde)

Quantum resistivity SdH osillation under high magnetic field. (Image by ZHU Xiangde)