ANDREEV TUNNELING INTO A ONE-DIMENSIONAL JOSEPHSON-JUNCTION ARRAY

In this letter we consider Andreev tunnelling between a normal metal and a one-dimensional Josephson junction array with finite-range Coulomb energy. The I-V characteristics strongly deviate from the classical linear Andreev current. We show that the non-linear conductance possesses interesting scaling behaviour when the chain undergoes a T = 0 superconductor-insulator transition. When the chain is superconducting, the low-lying excitations are gapless and the I-V curves are power law. When the chain is insulating the Andreev current is blocked up to a threshold voltage, proportional to the inverse correlation length of the chain, which vanishes at the transition point.