New types of instabilities in nonequilibrium excitation of a superconductor
Baru V.G. , Sukhanov A.A.
It is shown that when the nonequilibrium quasiparticles reach a critical density, a superconductor becomes unstable against a transition to an inhomogeneous state with a periodically modulated gap Δ. At the same time, an instability of a different type arises and corresponds to a transition to a homogeneous state with superconducting velocity Vs.