Transport properties of Bi₄Br₄ based Josephson weak links

Josephson weak links can host Andreev bound states that mediate the tunnelling of Cooper pairs through the barrier. Topological insulators are key hosting platforms of dissipationless carrier transport where electrons can flow through the edge states without any backscattering. In this work, we theoretically analyse a Josephson weak link based on the edges of monolayer Bi₄Br₄ connecting two superconducting leads. The monolayer Bi₄Br₄ is a unique two-dimensional topological insulator with negligible quantum confinement and highly stable edge states at room temperature. To explore quantum transport properties of this potential Josephson weak link, we carry out density functional theory, quantum transport modeling, and density functional perturbation theory based first-principles calculations. We calculate Andreev bound-state spectra as a function of phase difference to explore the topological superconductivity and bound states regime. Based on these data, we compute current–phase relation to demonstrate a variety of transport regimes. We also simulate microwave spectroscopy to explore the quantum tunnelling process through the Josephson weak link.