A new lead alloy for Josephson junctions

We have investigated a new ternary superconducting alloy applicable to Josephson junction circuit fabrication. The alloy is composed of lead, chromium, and gold. The energy gap of the alloy, based on derivative measurements on tunneling junctions, is approximately 2.64 meV at 4.2 K and the superconducting transition temperature is 7.6 K. Tunneling-junction characteristics based on this new alloy show very low subgap leakage and are suitable for logic and mixing applications. The alloy is strongly corrosion-resistant and adheres well to silicon and glass substrates.