Phase transitions in nonequilibrium superconductors induced by quasiparticle injection

We discuss the phase transitions induced by the injection of quasiparticles in nonequilibrium superconductors, based upon the equations of Scalapino and Huberman and including nonlinear effects. When the effect of the reaction of quasiparticles with phonons is small the system shows a first-order transition to an inhomogeneous state. As the effect of the reaction becomes larger, the transition becomes of second order. When the effect of the reaction is further increased, the system shows the first-order transition to the homogeneous normal state as was predicted by Owen and Scalapino. The results are in qualitative agreement with the recent experiments of Iguchi. The relation of the present problem to the spinodal decomposition is discussed