Synthesis and Fabrication of A15 Compounds for Superconducting Quantum Electronics

Recent advances in quantum technology have sparked interest in compound superconductors for fault-tolerant quantum circuits and superconducting detectors. Here, we review the potential for A15 superconductors to be integrated into quantum electronics. A15 intermetallic compounds are a family of cubic superconductors with critical temperatures up to 23 K. A15s were subjected to intensive research until interest waned due to the discovery of superconductivity in cuprates in the 1970s. In our work, we revisit A15s as promising superconducting alloys for applications where high kinetic inductance is required. We surveyed the literature for the various growth and characterization data available on 20+ A15 compounds, and we found that more than half of them were grown as single crystals, but thin film samples were able to achieve the highest critical temperatures. Additionally, A15 materials exhibit high disorder as evidenced by large critical fields, although this information is mostly available for bulk crystals. To fully assess the compatibility of A15s with superconducting circuits, further studies on their thin-film growth and cryogenic microwave characterization will be essential.