Determination of the Superconductor-Insulator Phase Diagram for One-Dimensional Wires

We establish the superconductor-insulator phase diagram for quasi-one-dimensional wires by measuring a large set of MoGe nanowires. This diagram is roughly consistent with the Chakravarty-Schmid-Bulgadaev phase boundary, namely, with the critical resistance being equal to R(Q)=h/4e(2). Deviations from this boundary for a small fraction of the samples prompt us to suggest an alternative phase diagram, which matches the data exactly. Transport properties of wires in the superconducting phase are dominated by phase slips, whereas insulating nanowires exhibit a weak Coulomb blockade behavior.