Spatially Resolved Nonlinearity Measurements of YBa$_2$Cu$_3$O$_{7-d}$ Bi-crystal Grain Boundaries

Sheng-Chiang Lee; Steven M. Anlage

doi:10.1063/1.1561152

paper

Spatially Resolved Nonlinearity Measurements of YBa $_{2}$ Cu $_{3}$ O $_{7 - d}$ Bi-crystal Grain Boundaries

arXiv:cond-mat/0210055 · doi:10.1063/1.1561152

Abstract

We have developed a near-field microwave microscope to locally excite a superconducting film and measure second and third harmonic responses at microwave frequencies. We study the local nonlinear response of a YBa $_{2}$ Cu $_{3}$ O $_{7 - d}$ thin film grown on a bi-crystal SrTiO $_{3}$ substrate. The location of the bi-crystal grain boundary is clearly identified by the microscope through higher harmonic response, and the spatial resolution is on the order of the magnetic loop probe size, about 500 $μ m$ . The harmonic power and spatial resolution are successfully modeled with a one-dimensional extended Josephson junction simulation. From the model, the 2nd order harmonic response is dominated by Josephson vortex generation and flow. A geometry-free nonlinear scaling current density $J_{N L} ≃ 1 0^{4} \sim 1 0^{5} A / c m^{2}$ is also exstracted from the data, indicating that the grain boundary weak link is the dominant nonlinear source in this case.

arXiv comment4pages, 4figures

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Nonlinear Meissner Effect in CuO Superconductors

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Abstract

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Spatially Resolved Nonlinearity Measurements of YBa $_{2}$ Cu $_{3}$ O $_{7 - d}$ Bi-crystal Grain Boundaries