RESEARCH

Achievements

Prof. Jian Wang and collaborators discovered the interface superconductivity in topological-kagome-magnet/metal heterostructure

Time：2023-11-03Author：王健ClickTimes：_showDynClicks("wbnews", 1634188721, 5771)

In 2016, for the first time, Prof. Jian Wang’s group at Peking University and collaborators reported the observation of superconductivity at the interface between three-dimensional topological Dirac semimetal Cd_{3}As_{2} crystals and non-superconducting metallic tips. Subsequently, Prof. Jian Wang’s group detected superconductivity at the interfaces between topological Weyl semimetals and non-superconducting metallic tips. Due to the topological non-trivial band structures of topological metals and semimetals, the superconducting states emerging at their surfaces may inherit the topological non-trivial properties and become topological superconducting states, which have important potential applications in topological quantum computing.

Recently, the Kagome magnet TbMn_{6}Sn_{6 }has attracted extensive attention. In TbMn_{6}Sn_{6}, the Kagome lattice formed by Mn atoms has the opposite magnetic moments of Tb atoms along the out-of-plane direction, exhibiting a ferrimagnetic ground state with a Curie temperature of 423 K. Previous theoretical works proposed that in the Kagome lattice, strong spin-orbit coupling and out-of-plane ferromagnetic ordering would generate Chern gapped Dirac fermions, which has been detected by experiments. As a typical magnetic Kagome topological metal, TbMn_{6}Sn_{6} is non-superconducting.

Recently, Prof. Jian Wang, Prof. X. C. Xie, Prof. Shuang Jia and Prof. Peng Gao at Peking University, in collaboration with Dr. He Wang at Capital Normal University, Prof. Hua Jiang at Soochow University, and Prof. Ziqiang Wang at Boston College, discovered emergent superconductivity at the interface between topological-kagome-magnet TbMn_{6}Sn_{6} and non-superconducting metal heterostructures. Experimental results indicate that the emergence of superconductivity at the interface is closely related to the ferrimagnetism of TbMn_{6}Sn_{6}, and the superconducting state is quasi-two-dimensional. Taking into account the spin-orbit coupling, the observed interface superconductivity can be a surprising and more realistic realization of the *p*-wave topological superconductors theoretically proposed for two-dimensional semiconductors proximity-coupled to *s*-wave superconductors and insulating ferromagnets, providing a new direction for studying spin-triplet pairing and topological superconductivity.

As shown in Fig. 1a, Prof. Jian Wang’s group successfully detected the superconducting signal by depositing non-superconducting metallic thin films on the (001) surface of TbMn_{6}Sn_{6} samples via interface engineering. The superconducting state emerging on the (001) surface after film deposition shows hysteretic magnetoresistance, indicating that this superconducting state can coexist with ferromagnetism (Fig. 1b). Furthermore, the quasi-two-dimensional superconductivity of TbMn_{6}Sn_{6}/metal heterostructure is revealed by angle-dependent transport experiments(Fig. 1c and 1d). In addition, the emergent superconductivity was also detected in the heterostructures formed by different types of non-superconducting metallic tips and TbMn_{6}Sn_{6} through point contact spectroscopy (Fig. 1e). Consistent with the TbMn_{6}Sn_{6}/metal film heterostructure, the superconducting state at the point contact also shows the magnetic hysteresis (Fig. 1f).

**Figure 1 The emergent superconductivity at the interface of TbMn _{6}Sn_{6}/metal heterostructures.**

The observation of superconductivity in topological-kagome-magnet/metal heterostructures has important physical significance for studying topological superconductivity. Theoretically, the topological superconductivity can be induced by stacking an *s*-wave superconductor, a two-dimensional semiconductor with Rashba spin-orbit coupling, and a ferromagnetic insulator to form a heterostructure (Fig. 2a). However, this proposal has not been experimentally realized yet. In this work, these challenges are overcome in the TbMn_{6}Sn_{6}/metal heterostructures (Fig. 2b), since the quasi-two-dimensional superconductivity coupled with the magnetization and strong SOC are all established at the interface, thus providing a more realistic material platform for realizing chiral topological superconductivity (Fig. 2c). Moreover, it is worth mentioning that TbMn_{6}Sn_{6} is a typical topological magnetic material with a Curie temperature as high as 423 K. Our work is the first report of emergent superconductivity in a material system with a Curie temperature above room temperature.

**Figure 2 The theoretical scenario for the interface superconductivity of TbMn _{6}Sn_{6}/metal heterostructure. a** The strategy of the proximity-induced topological superconductivity in stacked layers formed by an

The paper was published online by *Nature Communications* on November 2, 2023. Link to the paper: https://www.nature.com/articles/s41467-023-42779-1. Jian Wang and Ziqiang Wang are the corresponding authors. He Wang, Yanzhao Liu, Ming Gong, and Hua Jiang contributed equally to this work. This work was supported by Beijing Natural Science Foundation, National Key Research and Development Program of China, National Natural Science Foundation of China, China Postdoctoral Science Foundation, Capacity Building for Sci-Tech Innovation-Fundamental Scientific Research Funds, U.S. Department of Energy, Basic Energy Sciences, and the Cottrell SEED Award from Research Corporation for Science Advancement.