Microwave Nonlinearities of an Isolated Long YBa₂Cu₃O(7-d) Bi-crystal Grain Boundary

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We measure the local harmonic generation from an YBa₂Cu₃O(7-d)(YBCO) bi-crystal grain boundary to examine the local Josephson nonlinearities. Spatially resolved images of second and third harmonic signals generated by the grain boundary are shown. The harmonic generation and the vortex dynamics along the grain boundary are modeled with the Extended Resistively Shunted Josephson (ERSJ) array model, which shows reasonable agreement with the experimental data. The model also gives qualitative insight into the vortex dynamics induced in the junction by the probing current distribution. A characteristic nonlinearity scaling current density JNL 1.5 x 10⁵ A/cm² for the Josephson nonlinearity is also extracted.