Nonequilibrium superconductivity based on quasithermal phonon and quasiparticle distributions

A new phenomenological model describing nonequilibrium superconductivity is proposed which is characterized by the introduction of a quasithermal distribution of phonons with energies of 0–∞. The model exhibits ${\mu }^{\mathrm{*}}$-model-like and $T^{\mathrm{*}}$-model-like Δ vs n and ${\mu }^{\mathrm{*}}$ vs n characteristics when the excess quasiparticle density n is low and high, respectively. The estimated critical density $n_c$ for the onset of instability is much lower than that of the ${\mu }^{\mathrm{*}}$ model. These results are in fairly good agreement with the experimental results reported by Willemsen and Gray, and Akoh and Kajimura.