Superconducting diode as high-frequency sound detector

The properties of a broadband sound detector utilising microwave-phonon-assisted tunnelling in superconductors are described. Using Al¿Pb tunnel diodes at 1.3°K, the sensitivity of the detector to 9.3 × 109 c/s sound waves was found to be approximately 2 × 10¿4 V/W cm¿2. At high frequencies the sensitivity is expected to increase as the square of the sound frequency.