Effect of a compressive uniaxial strain on the critical current density of grain boundaries in superconducting YBa2Cu3O7-delta 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 Jc. The removal of strain from the superconducting grain boundary channels by the application of compressive strain causes a remarkable increase in Jc. Contrary to previous understanding, the strain-free Jc of the grain boundary channels is comparable to the intrinsic Jc of the grains themselves.