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

TL;DR

This study demonstrates that monolayer Fe(Te,Se) grown on Bi2Te3 exhibits tunable superconductivity and topological electronic structures, providing a promising platform for realizing Majorana bound states crucial for quantum computing.

Contribution

The paper reports the growth and characterization of monolayer Fe(Te,Se)/Bi2Te3 heterostructures, revealing tunable electronic and spin structures conducive to Majorana states, advancing interface engineering for topological quantum devices.

Findings

Superconductivity observed in monolayer Fe(Te,Se) on Bi2Te3.

Tuning doping levels alters the electronic structure and spin-momentum locking.

Reduced doping enhances conditions for Majorana bound states.

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.