Quasiparticle-energy distributions in optically illuminated Al-PbBi superconducting tunnel junctions

Nonequilibrium quasiparticle-energy distributions in weakly illuminated aluminum-aluminum-oxide-lead-bismuth tunnel junctions are obtained from current-voltage characteristics. A highly accurate method of unfolding $I\left(V\right)\mathrm{}$ to deduce $f\left(E\right)\mathrm{}$ is presented which is applicable for asymmetric-tunnel-junction analysis. Illumination from either side of the tunnel junction was performed, with differing resulting tunneling behavior. The unfolded results in both cases are in good agreement with a $T^{*}$ description of the nonequilibrium quasiparticle distribution on the aluminum side.