Mapping the phase diagram of a YBa$_2$Cu$_3$O$_{7-\delta}$ nanowire through electromigration

We use electromigration (EM) to tune the oxygen content of YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) nanowi\-res. During EM, the dopant oxygen atoms in the nanowire are moved under the combined effect of electrostatic force and Joule heating. The EM current can be tuned to either deplete or replenish nanowires with oxygen, allowing fine tuning of its hole doping level. Electrical transport measurements and Kelvin probe microscopy corroborate good homogeneity of the doping level along the electromigrated nanowires. Thus, EM provides an effective method to study transport properties of YBCO in a wide doping range at the nanoscale in one and the same device.