For a long time, topological superconductors have received extensive attention for their research in Majorana fermions and potential applications in topological quantum devices. However, intrinsic topological superconducting materials are very rare. In recent years, theoretical and experimental studies have shown that in addition to intrinsic topological superconducting materials, the use of topological insulators and topological semi-metallic materials with non-trivial energy band structures provides a possible way to achieve topological superconductivity. Most research groups use doping, high voltage, or through the proximity effect to induce possible topological superconductivity in topological insulators and topological semimetals. In 2016 and 2017, the Wang Jian research group of Peking University and the Goutam Sheet research group of the Indian Institute of Science and Education independently used point contact methods to induce superconducting signals on topological materials such as Cd3As2 and TaAs. This method of inducing superconductivity through metal needle tips provides new ideas for achieving superconductivity in topological materials. However, the inherent mechanism is still unclear. On the other hand, the superconductivity induced by this method is limited to the vicinity of the needle tip. .
The SC10 group of the State Key Laboratory of Superconductivity, Institute of Physics, Chinese Academy of Sciences / National Research Center for Condensed Matter Physics in Beijing (Former Researcher of the Institute of Physics) The team focuses on the point contact and scanning tunneling studies of superconductivity and topological materials. In recent years, the two teams have cooperated closely and jointly tackled problems in an attempt to achieve superconductivity in a variety of topological materials. The postdoctoral fellow He Junbao and Ph.D. student Chen Dong (graduated), supervised by Chen Genfu, the State Key Laboratory of Superconductivity at the Institute of Physics, have successfully grown topological semimetal tungsten carbide crystals with triple degenerate points near the Fermi surface 95, 195165 (2017)). The research team used point contact methods to successfully induce superconductivity on WC using ordinary metal needle tips or even magnetic metal needle tips. In order to further understand the role of the metal needle tip in the experiment, the team member SC10 group doctoral student Zhu Wenliang, postdoctoral Hou Xingyuan, and doctoral student Li Jing (graduated) etc. under the guidance of two teachers used magnetron sputtering coating method to deposit on WC surface A variety of non-magnetic and magnetic metal films were prepared, and then point contact junctions were prepared with silver glue on the deposited metal films, and the Andreev reflection spectrum of the superconductivity of the mark was observed. The experiment completely ruled out the local pressure of the needle tip and the size limiting effect and other factors, indicating that the coupling between the topological material and the metal is the main mechanism for the occurrence of superconductivity. Moreover, the use of a magnetic needle tip or magnetic thin film to induce superconductivity suggests that the interface superconductivity may have a spin-tristate paired composition. In addition, the method of achieving superconductivity of the metal / topological material interface by coating is simple and easy to use, and may be suitable for other measurement methods in the future, so as to further understand the characteristics and generation mechanism of superconductivity.