Phonon Generation and Detection in Superconducting Lead Diodes

Abstract
We present a detailed experimental study of the behavior of Pb-Pb superconducting diodes in phonon generation and detection. It is shown that the detection process occurs via pair breaking as well as phonon-assisted tunneling. The present experimental results do not resolve the distribution in energy of the phonons emitted by the generator. However, the derivative of the detected signal with respect to the generator current contains well-defined structure coincident with the phonon density of states of Pb calculated by McMillan and Rowell.