Inducing superconductivity in epitaxial topological insulator-based heterostructures

Cequn Li, Department of Physics, Pennsylvania State University

Topological insulator/superconductor heterostructures are a potential platform for topological quantum computing as they may support Majorana zero modes. Pioneered by the confinement heteroepitaxy of 2D metals at Penn State¹, we are able to synthesize high-quality, large-area topological insulator/superconductor heterostructures. In this talk, I will present our work in probing proximity-induced superconductivity in epitaxial (Bi,Sb)₂Te₃ (BST)/graphene (Gr)/2L-Ga heterostructures using transport measurements². We develop clean, lithography-free van der Waals tunnel junctions, which allow mesoscopic transport characterizations in ambient conditions. We perform transport tunneling spectroscopy measurements and observe two superconducting gaps in the tunneling spectra. One gap agrees with the SC gap of the 2L-Ga. We attribute the second gap to proximity-induced superconductivity in the Dirac surface state of the BST film. In 5QL BST/Gr/Ga films, the induced gap is approximately 0.2 meV, which is about 40% of the SC gap in 2L-Ga. In addition, we observe discrete tunneling conductance jumps corresponding to the addition of a single vortex when a magnetic field is applied.

1. Natalie Briggs et al., Nat. Mater. 19, 637–643 (2020)

2. Cequn Li et al., Nat. Mater. 22, 570–575 (2023)

Hosted by Katja Nowack (LASSP) and Valla Fatemi (AEP). Please email kicnano@cornell.edu for the Zoom link.