The effect of quasiparticle self-generation on the performance of small gap multiple tunnelling STJs

Due to the slowness of the electron–phonon interaction in small gap STJs currently being developed as the latest generation of photon detectors, during the device operation a broad statistical distribution of interacting quasiparticles and phonons is established. This gives rise to new physical phenomena and also renders the traditional Rothwarf–Taylor model completely inadequate for the analysis of quasiparticle and phonon dynamics for all traditional superconductors except unproximised Nb. We have developed a new kinetic approach replacing the Rothwarf–Taylor scheme. We demonstrate the results of experimental and theoretical studies of the new physical phenomenon of quasiparticle self-generation in a heavily proximised multiple tunneling Ta/Al STJ and discuss the implications of the observed quasiparticle self-generation for photon detection.