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

Low-angle grain boundaries (GBs) in superconductors exhibit intermediate Abrikosov vortices with Josephson cores, whose length l along GB is smaller than the London penetration depth, but larger than the coherence length. We found an exact solution for a periodic vortex structure moving along GBs in a magnetic field H and calculated the flux flow resistivity RFH, and the nonlinear voltage-current characteristics. The predicted RFH dependence describes well our experimental data on 7± unirradiated and irradiated YBa2Cu3O7 bicrystals, from which the core size lT, and the intrinsic depairing density JbT on nanoscales of a few GB dislocations were measured for the first time. The observed J_bT= J_b01 (T-Tc)^2 indicates a significant order parameter suppression on GB.