  Charge transport in a high-transmission single-mode long SINIS junction (S
stands for superconductor, I is an insulator, and N is a normal metal) is
considered in the limit of low bias voltages and low temperatures. The kinetic
equation for the quasiparticle distribution on the Andreev levels is derived
taking into account both inelastic relaxation and voltage-driven Zener
transitions between the levels. We show that, for a long junction when the
number of levels is large, the Zener transitions enhance the action of each
other and lead to a drastic increase of the dc current far above the critical
Josephson current of the junction.
