Shaping the superconducting properties of nanoscale junctions by electromigration

High current densities in small metallic junctions can produce electron-assisted atomic diffusion known since the 60’s as responsible for failures in metallic interconnections. Controlling and using this phenomena permits one to tune the material superconducting properties at the nanoscale. Here we demonstrate the control and the reversibility of such phenomena for three types of superconductors: Al, Nb and LCCO. For the latter material, we show that selective migration of oxygen atoms and the consequent doping modification induces a transition from a superconducting state to an insulating state in a reversible way. For the case of Nb, high level control of the electromigration allowed us to locally change the material properties (superconducting critical temperature and normal state resistance) and, at the end, to generate the in situ formation of tunable weak links. Numerical simulations within the Ginzburg-Landau formalism are also presented and show excellent agreement with the experimental data. These findings provide an easy method for the in situ fabrication of weak links and pave the way for a reversible control of local properties of nanowires