Effect of a Compressive Uniaxial Strain on the Critical Current Density of Grain Boundaries in Superconducting YBa2Cu3O7-δ Films

The mechanism by which grain boundaries impede current flow in high-temperature superconductors has resisted explanation for over two decades. We provide evidence that the strain fields around grain boundary dislocations in YBa2Cu3O7-delta thin films substantially suppress the local critical current density J(c). The removal of strain from the superconducting grain boundary channels by the application of compressive strain causes a remarkable increase in J(c). Contrary to previous understanding, the strain-free J(c) of the grain boundary channels is comparable to the intrinsic J(c) of the grains themselves.