Superconductivity at Pd/Bi₂Se₃ Interfaces Due to Self-Formed PdBiSe Interlayers

Understanding the physical and chemical processes at the interfaces of metals and topological insulators is crucial for the development of the next generation of topological quantum devices. Here, we report the discovery of robust superconductivity in Pd/Bi₂Se₃ bilayers fabricated by sputtering Pd on the surface of Bi₂Se₃. Through transmission electron microscopy measurements, we identify that the observed interfacial superconductivity originates from the diffusion of Pd into Bi₂Se₃. In the diffusion region, Pd chemically reacts with Bi₂Se₃ and forms a layer of PdBiSe, a known superconductor with a bulk transition temperature of 1.5 K. Our work provides a method for the introduction of superconductivity into Bi₂Se₃, laying the foundation for the development of sophisticated Bi₂Se₃-based topological devices.