Nonlinear Proximity Effect in a Hybrid Normal Metal-Superconductor Structure

Effective-field microscopic approach has been applied to a hybrid structure “normal metal-superconductor” in order to describe a nonlinear proximity effect. It is shown that at high barrier transparency, the phase transition to a superconducting state disappears abruptly. The existence of two gaps points out the intermediate state typical for a firstorder phase transition. The incoherent electron tunneling enlarges the temperature region of the nonequilibrium superconductivity.