Transients in nonequilibrium superconductors

The superconducting gap and the quasiparticle and phonon-distribution functions are studied as functions of time following the sudden turning on or off of tunneling current or microwaves. They are studied by numerical integration of the Boltzmann equations which Chang and Scalapino have solved for the steady state. The initial response times show no temperature dependence in the range $(0.9\mathrm{}-0.96)T_c$. The initial response times of the gap are different when the drive is turned on and when it is turned off. This shows the effect of an additional time scale: the time scale for saturation of the driving mechanism. Finally, the possibility of the sample overshooting the steady state is demonstrated.