Flux flow of Abrikosov-Josephson vortices along grain boundaries in high-temperature superconductors

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We show that low-angle grain boundaries (GB) in high-temperature superconductors exhibit intermediate Abrikosov vortices with Josephson cores, whose length l along GB is smaller that the London penetration depth, but larger than the coherence length. We found an exact solution for a periodic vortex structure moving along GB in a magnetic field H and calculated the flux flow resistivity RF(H), and the nonlinear voltage-current characteristics. The predicted RF(H) dependence describes well our experimental data on 7∘ unirradiated and irradiated YBa₂Cu₃O₇ bicrystals, from which the core size l(T), and the intrinsic depairing density Jb(T) on nanoscales of few GB dislocations were measured for the first time. The observed temperature dependence of Jb(T)=Jb₀(1-T/Tc)² indicates a significant order parameter suppression in current channels between GB dislocation cores.