AC LONG-RANGE PHASE-COHERENT EFFECTS IN MESOSCOPIC SUPERCONDUCTOR NORMAL-METAL STRUCTURES

We calculate the conductance of a normal metal film (N) in contact wit h two superconductors (S) in the presence of a constant ((V) over bar S) and oscillating (V-omega cos omega t) bias voltage between N and S. It is shown that the conductance as a function of (V) over bar(S) has a Shapiro-like step at (V) over bar(S) = HBAR omega/2e. This exists e ven in the case when the spacing between two superconductors largely e xceeds the coherence length in the normal metal, and the critical Jose phson current is exponentially small. The amplitude of the Shapiro ste p decreases slowly with increasing temperature T in the form of T-1.