Imaging of electromagnetic resonances in a ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ bicrystal grain-boundary Josephson junction

We report on spatially resolved measurements of dynamic states of a high-critical-temperature superconductor Josephson junction. The experiments were performed with a ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ thin-film grain-boundary Josephson junction fabricated on an yttria-stabilized zirconia bicrystal substrate. We identified the excitation of one-dimensional self-resonant cavity modes (Fiske resonances) with a spatial resolution of about 1–3 μm using low-temperature scanning electron microscopy. Our imaging results with this Josephson junction are in fair agreement with results obtained with high-quality Nb/${\mathrm{AlO}}_{\mathit{x}}$/Nb tunnel junctions having a uniform dielectric tunnel barrier.