Energy Gap, Microwave-Assisted Tunneling, and Josephson Steps in Thin-Film Weak Links at 63 and 302 GHz

We present experimental evidence for the occurrence of energy-gap structure and microwave-assisted tunneling in the $\mathrm{IV}$ curves for superconducting thin-film weak links. From measurements of the power and the temperature dependence of the Josephson steps we argue that also the Riedel peak is observable in weak links.