Nonlocal in-plane Resistance in High-T c Superconducting Films in the Vicinity of a Kosterlitz-Thouless-Type Transition

We have measured the nonlocal in-plane resistance in high-T_csuperconducting Yba₂Cu₃O_7–dfilms. The results obtained in zero magnetic field show a negative nonlocal resistance in the vicinity of the Kosterlitz-Thouless-type vortex-antivortex unbinding transition, as it was predicted recently by Wortis and Huse [Phys. Rev. B54, 12413 (1996)]. We also found that the negative nonlocal resistance takes place within a certain domain of the current-temperature diagram. Our findings indicate that nonlocal measurements in planar geometry can be a new method to study vortex dynamics in superconductors.