Abstract
The kinetic equation is used to compute the elastic and inelastic quasiparticle branch mixing rates for a superconducting film into which quasiparticles are injected via a tunnel barrier from a second superconducting film. Representative graphs are presented of the steady-state quasiparticle distribution, the quasiparticle charge imbalance versus injection current, the charge relaxation rate vs for several values of elastic scattering rate, and the quasiparticle branch relaxation rate as a function of energy. The quasiparticle potential developed in the injection film is related to and thence to a characteristic electron-phonon scattering time. Detailed measurements of are reported for films of superconducting A1, some of which were doped with oxygen to give a range of transition temperatures from 1.2 to 2.1 K. From the dependence of on , values are deduced for the gap anisotropy of the films. In the cleanest samples, μ sec, a value that is in good agreement with energy-gap relaxation and - phonon (phonons of energy ) mean-free-path measurements, but a factor of about 4 smaller than that obtained from recombination time measurements and theoretical calculations. The value of in the A1 films increases with the transition temperature as or , instead of as predicted by simple theory. It is suggested that the rapid increase of with may arise from either a strong dependence of on or from a small concentration of magnetic impurities.
- Received 26 September 1978
DOI:https://doi.org/10.1103/PhysRevB.19.4495
©1979 American Physical Society