Josephson Junctions with Two-Dimensional van der Waals Tunnel Barrier

Better device structure and materials control have contributed to the performance improvement of the Al/AlO_x/Al-based superconducting qubits, allowing the technology to initiate practical applications in quantum computing. However, one current limitation of such qubits is the use of amorphous alumina as the tunnel barrier, which is known to have defects that may compromise the qubit coherent time and performance stability. Here, we report novel Josephson Junctions with 2D van der Waals tunnel barriers made with stacked N-layer MoS₂ that has minimal number of defects. We first generate a MoS₂ membrane with controlled layer number N by vacuum stacking monolayer MoS₂ as the tunneling barrier, and then depositing Al superconductor on either side to form the Josephson junctions. We show that we can reliably fabricate large numbers of Josephson junction devices on a single chip, and they show critical supercurrent that can be directly tuned by changing the N. We also characterize the microwave properties of Al/MoS2/Al junctions in a bulk superconducting cavity. Our work offers a new, powerful platform for generating and studying novel qubits with diverse 2D materials, and thus may provide an additional route to further improve the qubit performance for advancing the quantum technology.