Asymmetric vortex entry and nonreciprocal supercurrents in a proximitized Mo–Re two-band/two-gap superconductor

Nonreciprocity refers to a phenomenon in which a system’s response, such as wave transmission or current flow, depends on the direction of propagation. In superconductors, this manifests as the superconducting diode effect, where the maximum critical supercurrent differs for opposite directions of flow. Here, we report the first observation of such an effect in a two-gap transition-metal alloy, achieving a 17% diode efficiency through a single-step process using molybdenum–rhenium thin films with asymmetric silver overlayer deposition. Our results establish multigap superconductors as a promising platform for realizing superconducting diodes, which offer access to unique physical regimes arising from distinct proximity couplings of the normal overlayer with large- and small-gap condensates. Furthermore, we demonstrate that simple proximity engineering with noble metals can yield competitive superconducting diode efficiencies compatible with standard thin-film fabrication techniques. This work not only raises fundamental questions about the interplay between two-gap superconductivity and nonreciprocal transport but also outlines a practical route toward new cryogenic electronic applications.