Investigation of Dynamic Behaviors of Low-Level Dissipation at ${rm YBa}_{2}{rm Cu}_{3}{rm O}_{7}$ Grain Boundaries Using Low-Temperature Near-Field Scanning Microwave Microscopy

摘要

Near-field scanning microwave microscopy (NSMM) provides a unique nondestructive approach for detection of local dissipation with high sensitivity and high spatial resolution. With recently improved NSMM probes of spatial resolution of up to 400 nm ($sim 10^{-6}$ wavelength), detection of dissipation was achieved on YBCO microbridges at currents more than three orders of magnitude below the $J_{c}(T)$. In this work, we report characterization of the dynamic behavior of low-level dissipation at the grain boundary of ${rm YBa}_{2}{rm Cu}_{3}{rm O}_{7-delta}$ microbridges as function of time and applied electrical current. On higher-angle grain boundary, the dissipation develops rapidly with increasing current and shows approximately linear dependence on current. On lower-angle grain boundary, nonlinear features were observed and attributed to bi-modal pattern of dissipation evolution of nucleation of isolated hot spots and their evolution. Comparison with the similar ${rm NSMM}+IV$ measurement made on the “bulk” part of the same ${rm YBa}_{2}{rm Cu}_{3}{rm O}_{7-delta}$ microbridges on a reduced temperature scale shows higher dissipation on the grain boundary can be mostly attributed to the lower $T_{c}$ values on grain boundaries.