Tunneling Characteristics of a Nonequilibrium Double Junction

The use of a double tunnel junction to investigate the nonequilibrium quasiparticle distribution due to tunnel injection has been studied. I give quantitative explanations of the sharp structures and the asymmetric effects observed by Kaplan, Kirtley, and Langenberg in the second derivative of the $I\left(V\right)\mathrm{}$ characteristics of the driven detector junction. It is suggested that the energy- and temperature-dependent inelastic quasiparticle relaxation time, as well as the elastic-scattering branch-mixing time, can be extracted from these sharp structures and the asymmetric effects.