Distribution of nonequilibrium excitations and phonon generation in superconducting tunnel junctions
Abstract
On the basis of the complete system of equations which describe the nonequilibrium states of S1–I–S2 tunnel junctions caused by a quasiparticle current, distributions are obtained of the electron excitations in S-films of a symmetric junction (identical films forming a tunnel junction) for arbitrary transparencies of the tunnel barrier in the case T⪡Δ,eV—2Δ ⪡2Δ (eV is the applied voltage, and Δ is the energy gap). The effect of suppressing the superconductivity in the nonequilibrium state (eV > 2Δ) is considered. A theory is given for the generation of phonons with the frequency ω ≥ 2Δ by quasiparticle tunneling. Results of already known experiments are explained and new features of the distribution of recombination phonons being generated are predicted.