COHERENCE EFFECTS IN A NORMAL-METAL-INSULATOR-SUPERCONDUCTOR JUNCTION

Coherence effects arising due to Andreev reflections in a superconductor-insulator-normal-metal junction are considered. It is shown that in the absence of electron-electron interaction in the metal at low temperatures, the electrical potential drop on the insulator I(O)R(1), caused by the current density I-O through the junction, vanishes, although the resistance of the device R(infinity) measured by the two-probe method can be large. The electron-electron interaction determines the zero-temperature value of R(I). The implications of these effects for the theory of the superconductor-normal-metal-superconductor junction are discussed.