Precise control of the doping in cuprate high-Tc superconductors is fundamental for studying the phase diagram of these materials, and can have a crucial role for technological applications. We recently developed a novel procedure, in order to tune the doping of YBCO nanostructures by using an ex-situ electromigration (EM). On this topic, we have recently published two papers.
In the first work, published on Physical Review Applied and featured as editors’ suggestion (link), we have shown that an AC biasing scheme allows to fine tune the oxygen content in our nanowires. A phase diagram, in good agreement with that of bulk YBCO, can be built using a single nanowire and successive steps of EM. Kelvin Probe Atomic Force Microscopy, used to investigate homogeneity of the nanowires after EM, confirmed the uniform distribution of oxygen atoms within the nanowires.
In the second work, published on Superconductor Science and Technology (link), we have used EM to tune the superconducting properties of nanowires-based SQUIDs. Here, EM is instrumental to suppress the critical current of the SQUID, therefore enhancing the voltage modulation depth by factors as high as 8. This result shows that EM can be used to significantly improve the nanoSQUIDs performances. Moreover, this technique can be extended to a large range of devices: indeed, it is particularly well suited for constriction type weak links and grooved Dayem bridges, where EM is expected to occur locally.
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