Electrolyte Gating of YBCO Josephson Junctions

We report low-temperature transport measurements of electrolyte-gated Josephson junctions in thin films of YBa$_{2}$Cu$_{3}$O$_{7-d}$. The junctions are formed using ion damage from a 0.5 nm focused He-ion beam, allowing for junction barriers down to a few nm in length. The barrier can be tuned continuously from a reduced T$_{C}$ superconductor to a normal metal to an insulator by varying the ion dose. We use an ionic liquid electrolyte combined with a thin protective layer of hexagonal Boron Nitride to reversibly modify the junction properties.