Microwave Nonlinearities of an Isolated Long YBa_2Cu_3O_(7-d) Bi-crystal Grain Boundary

TL;DR

This study investigates the local microwave nonlinearities in an YBCO bi-crystal grain boundary by measuring harmonic generation, modeling vortex dynamics, and identifying a characteristic nonlinearity scaling current density.

Contribution

It provides spatially resolved harmonic measurements and a model-based analysis of vortex dynamics in YBCO grain boundaries, revealing the nonlinear behavior and a key scaling current density.

Findings

Harmonic signals are spatially mapped along the grain boundary.

The ERSJ model agrees qualitatively with experimental data.

A characteristic nonlinearity scaling current density JNL is identified.

Abstract

We measure the local harmonic generation from an YBa_2Cu_3O_(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 10^5 A/cm^2 for the Josephson nonlinearity is also extracted.