ac Long-range phase-coherent effects in mesoscopic superconductor normal metal structures

We calculate the conductance of a normal metal film (N) in contact with 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 even in the case when the spacing between two superconductors largely exceeds the coherence length in the normal metal, and the critical Josephson current is exponentially small. The amplitude of the Shapiro step decreases slowly with increasing temperature T in the form of T-1.