Nonequilibrium superconductivity in spin-polarized superconducting tunneling junctions

The presence of an applied magnetic field can lead to important effects as regards the nonequilibrium properties of a superconductor when spin-flip scattering processes are taken into account. Here we consider spin-flip transitions due to spin-orbit scattering of the quasiparticles by impurities, and introduce the kinetic equations governing the quasiparticle and phonon excitations. We solve the kinetic equations for the case of a superconducting film in a magnetic field driven out of equilibrium by quasiparticle injection. We consider also two identical phonon-coupled superconducting tunneling junctions and calculate the current-voltage characteristics as a function of the applied magnetic field and the spin-orbit scattering rate. Our results provide a natural and simple interpretation of a recently reported experiment.