Strain-Induced Electric Fields in Superconducting Aluminum

Abstract
Electromagnetic waves are excited in Al-Pb superconducting tunnel junctions by compressional 9.3-GHz acoustic waves when the acoustic wave front makes a small angle with the plane of the tunnel junction. The electromagnetic waves are induced by the electrostatic field in the superconducting Al film which is due to the compressional strain gradient in the Al. This result provides experimental confirmation of the theories of Dessler et al. and Herring developed for the case of gravitation-induced strains.