The fractional Josephson effect in FeTe_0.55Se_0.45-based van der Waals Josephson junctions

Recently, FeTe_0.55Se_0.45 has emerged as a potential candidate for a topological superconductor. Its topologically non-trivial characteristics are expected to host Majorana zero-modes, making it an attractive platform for implementing fault-tolerant quantum computing. In this study, we fabricated FeTe_0.55Se_0.45-based van der Waals Josephson junctions using a micro-cleaving and stacking technique on a Peltier-cooled transfer stage. This fabrication ensures the high quality of the junction interfaces, confirmed by transmission electron microscopy. We observed the first odd-step missing of Shapiro steps, a signature of the fractional Josephson effect, which arises from a 4π-periodic supercurrent between Majorana zero-modes. Numerical calculations show good agreement with the experimental results, providing a quantitative estimate of the 4π-periodic supercurrent.