Gate Tunable Supercurrent in Lateral Josephson Junctions Based on Epitaxial Topological Insulator Thin Films

A topological insulator (TI) coupled to a superconductor is predicted to harbor an unusual form of superconductivity known as topological superconductivity (TSC). Over the past decade, the possibility of realizing the excitation of TSCs, i.e. Majorana zero modes, has generated much excitement, mainly due to its potential use in fault-tolerant topological quantum computations. The Majorana physics in TI/superconductor hybrid structures can be probed by fabricating a Josephson junction device in which the Dirac surface states of the TI layer serve as a weak connection. To date, most TI-based Josephson junctions are based on exfoliated TI flakes. However, for device fabrication and potential application in topological quantum computations, the molecular beam epitaxy (MBE)-grown wafer-scale TI films are much preferred. In this talk, we will introduce our recent progress on fabricating the lateral Josephson junction devices based on our MBE-grown (Bi,Sb)₂Te₃ films. By performing systematic measurements, we demonstrated that the induced superconductivity indeed arises in the TI’s Dirac surface states and found that the Josephson supercurrent can be altered by varying the bottom gates of the TI layer. Our findings advance the fundamental inquiries into Majorana physics in TI/superconductor hybrid devices.