Proximity-Effect-Induced Superconductivity In Bi2te3/Fese0.5te0.5 Thin-Film Heterostructures With Different Interface Conditions

Proximity-effect-induced superconductivity is studied for high-quality Bi2Te3/FeSe0.5Te0.5 (FST) thin-film heterostructures with atomically sharp interfaces and for Bi2Te3/TiO2/FST heterostructures where TiO2 is the ultrathin buffer layer. Adjusting the buffer layer thickness from zero to several nanometers is used to simulate different interface conditions: strongly, weakly, and zero-coupled interfaces. It is found that, for the strongly coupled interface, both the Bi2Te3 thin film and the FST have almost the same magnitude as the superconducting pair potential; for the weakly coupled interface, the pairing potential of the Bi2Te3 thin film exhibits an approximately exponential decay with the TiO2 buffer layer thickness. Our experimental results can be explained qualitatively by several theories under different interface conditions.