Monolayer superconductivity and tunable topological electronic structure at the Fe(Te,Se)/Bi₂Te₃ heterojunction

The interface between two-dimensional topological Dirac states and an s-wave superconductor is expected to support Majorana bound states that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin-orbit coupling to achieve spin-momentum locked topological surface states which are simultaneously superconducting. Here we investigate superconductivity in FeTe_1-xSe_x grown on Bi₂Te₃ by molecular beam epitaxy and present the interfacial spin and electronic structure with photoemission spectroscopy. We will show how superconductivity exists at the FeTe_1-xSe_x monolayer limit and describe how to systematically tune the interfacial topological and superconducting electronic structure through control over film growth conditions. We will describe how reducing Se doping not only reduces disorder from chemical inhomogeneities but improves the spin-momentum locking of the interfacial topological states. We will discuss how this platform can be optimized to advance efforts in Majorana interrogation and potential applications.