Contributed by: Jun Zhu, Cui-Zu Chang, Joshua Robinson, Danielle Hickey, and Yuval Oreg (Weitzmann Inst. of Sci.)
C. Li, Y.-F. Zhao, A. Vera, O. Lesser, H. Yi, S. Kumari, Z. Yan, C. Dong, T. Bowen, K. Wang, H. Wang, J. L. Thompson, K. Watanabe, T. Taniguchi, D. Reifsnyder Hickey Y. Oreg, J. A. Robinson, C.-Z. Chang, J. Zhu, "Proximity-Induced Superconductivity in Epitaxial Topological Insulator/Graphene/Gallium Heterostructures", Nature Materials, https://doi.org/10.1038/s41563-023-01478-4
The search for an unusual form of superconductivity known as topological superconductivity has attracted a great deal of attention of the quantum materials community because of its fundamental novelty and potential applications in fault-tolerant quantum computing technology. A hybrid structure of a topological insulator and an s-wave superconductor is expected to host topological superconductivity. A thin-film material platform is particularly useful in building devices and device applications.
An IRG team has developed a new synthetic approach to overcome prior growth challenges to realize a thin-film topological insulator/superconductor hybrid structure. This approach produced high-quality epitaxial (Bi,Sb)2Te3/graphene/two-atomic-layer gallium heterostructures with atomically abrupt interfaces that shows robust proximity-induced superconductivity in the Dirac surface states of the (Bi,Sb)2Te3 film, thus fulfilling a necessary step to the creation of a topological superconductor. This work paves the path to explorations of topological superconductivity and quantum computing circuitry in a scalable material platform.
What Has Been Achieved: The synthesis and measurement of epitaxial thin-film topological insulator/superconductor heterostructure leading to evidence for proximity-induced superconductivity in the surface states of the topological insulator. This combines confinement heteroepitaxy, a growth technique pioneered by members of the IRG, to synthesize graphene/Ga superconducting films, followed by the MBE growth of (Bi,Sb)2Te3 films. Van der Waals techniques are used to construct a clean, lithography-free tunnel junction and transport tunneling spectroscopy is used to obtain evidence for proximity-induced superconducting gap opening in the surface states of the (Bi,Sb)2Te3 film. Evidence of single vortex motion is observed. These measurements lay a foundation for the future exploration of topological superconductivity in this novel, large-area heterostructure.
Importance of the Achievement: A thin-film topological insulator-based hybrid structure that enables the studies of topological superconductivity and a potential quantum computing platform
How is the achievement related to the IRG, and how does it help it achieve its goals? The pursuit of topological superconductivity in scalable material platforms is a central objective of this IRG. Results demonstrated in this work is a significant step towards this goal. The combination of key expertise (confinement heteroepitaxy, MBE and van der Waals transport techniques from different team members is crucial to the success of this project.
News and Views on this result by Xiu, F. “Atomic heteroepitaxy for topological superconductivity” Nat. Materials (2023). https://doi.org/10.1038/s41563-023-01533-0