Transfer characteristics of phonon coupled superconducting tunnel junctions

Abstract

Abstract Results of theroretical and experimental investigations of the form of the transfer characteristics of phonon-coupled superconducting tunnel junctions are presented. In the ‘linear’ regime when quasiparticle densities are little deviated from their thermal values, the only outstanding feature is a gradient discontinuity which occurs when the generator voltage is large enough for quasiparticle relaxation processes to contribute to the density of detectable phonons. A fundamental theoretical treatment for this case gives an adequate qualitative description of observed structure and quantitative differences are tentatively attributed to inelastic scattering. Results in the ‘overinjection’ régime are much more complex. Some of the processes which may be expected to modify the spectrum of generated phonons and the detector response are discussed, and are shown to account qualitatively for the various features of the characteristics observed.