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

Abstract

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. While signatures of Majorana bound states have been observed in the magnetic vortex cores of bulk FeTe0.55Se0.45, inhomogeneity and disorder from doping makes these signatures unclear and inconsistent between vortices. Here we report superconductivity in monolayer FeTe1-ySey (Fe(Te,Se)) grown on Bi2Te3 by molecular beam epitaxy. Spin and angle resolved photoemission spectroscopy directly resolve the interfacial spin and electronic structure of Fe(Te,Se)/Bi2Te3 heterostructures. We find that for y = 0.25 the Fe(Te,Se) electronic structure overlaps with the topological Bi2Te3 interfacial states which disrupts the desired spin-momentum locking. In contrast, for y = 0.1 a smaller Fe(Te,Se) Fermi surface allows for clear spin-momentum locking observed in the topological states. Hence, we demonstrate the Fe(Te,Se)/Bi2Te3 system is a highly tunable platform for realizing Majorana bound states where reduced doping can improve characteristics important for Majorana interrogation and potential applications.

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• Resilient Growth of Highly Crystalline Topological Insulator-Superconductor Heterostructure Enabled by Ex-situ Nitride Film
• Mystery of superconductivity in FeTe films and the role of neighboring layers
• Interface-Enhanced Superconductivity in Ultrathin TiN Proximitized by Topological Insulators
• Ubiquity of rotational symmetry breaking in superconducting films, from Fe(Te,Se)/Bi${}_2$Te${}_3$ to Nb, and the effect of measurement geometry
• Unveiling In-Gap States and Majorana Zero Modes in Superconductor-Topological Insulator Bilayer model
• Tuning Carrier Type and Density in Highly Conductive and Infrared-Transparent (Bi1-xSbx)2Te3 films