Proximity-Induced Superconductivity in Epitaxial Topological Insulator/Graphene/Gallium Heterostructures

TL;DR

This paper demonstrates the growth of high-quality heterostructures combining topological insulators, graphene, and gallium, which exhibit proximity-induced superconductivity and potential Majorana zero modes for topological quantum computing.

Contribution

It introduces a scalable, atomically precise heterostructure platform that enables proximity-induced superconductivity in topological surface states, advancing topological quantum computing research.

Findings

Robust superconducting gap observed in heterostructures

Detection of a single Abrikosov vortex indicating Majorana modes

Development of a lithography-free tunneling spectroscopy method

Abstract

The introduction of superconductivity to the Dirac surface states of a topological insulator leads to a topological superconductor, which may support topological quantum computing through Majorana zero modes. The development of a scalable material platform is key to the realization of topological quantum computing. Here we report on the growth and properties of high-quality (Bi,Sb)2Te3/graphene/gallium heterostructures. Our synthetic approach enables atomically sharp layers at both hetero-interfaces, which in turn promotes proximity-induced superconductivity that originates in the gallium film. A lithography-free, van der Waals tunnel junction is developed to perform transport tunneling spectroscopy. We find a robust, proximity-induced superconducting gap formed in the Dirac surface states in 5-10 quintuple-layer (Bi,Sb)2Te3/graphene/gallium heterostructures. The presence of a single Abrikosov vortex, where the Majorana zero modes are expected to reside, manifests in discrete conductance changes. The present material platform opens up opportunities for understanding and harnessing the application potential of topological superconductivity.