Investigation of long-range superconducting proximity effects in Sb2Te3/FeSe0.5Te0.5 heterostructures with topological surface states

Abstract

This study investigates the interplay between superconductivity and topological surface states in heterostructures formed by combining the well-known three-dimensional topological insulator Sb2Te3 with the iron chalcogenide superconductor FeSe0.5Te0.5, which is characterized by its simple crystal structure and high critical field. Remarkably, even with a certain lattice mismatch between Sb2Te3 and FeSe0.5Te0.5, superconductivity is successfully induced on the surface of Sb2Te3 film, as demonstrated by the observation of a zero-resistance state. Based on this observation, we conducted a detailed investigation into the impact of Sb2Te3 film thickness on superconductivity in these heterostructures. Our results show that the superconducting transition temperature (Tc) decreases as the Sb2Te3 film thickness increases, yet remains unexpectedly high, even for films as thick as about 670 nm. This suggests that the long-range superconducting proximity effects in Sb2Te3 films are likely due to the topological surface states, which possess long mean free paths. The Sb2Se3/FeSe0.5Te0.5 heterostructure formed using Sb2Se3 without topological surface states, along with angle-resolved photoemission spectroscopy of Sb2Te3/FeSe0.5Te0.5, further suggested the possible coexistence of topological surface states and superconductivity in the Sb2Te3/FeSe0.5Te0.5 heterostructure. These findings offer an excellent platform for exploring the properties of topological superconductivity and detecting Majorana fermions.