Transformer Configuration in Three Dimensional Josephson Lattices at Zero Magnetic Field

Recent experiments on Bi₂Sr₂CaCu₂O_8-y superconductors at zero magnetic field have been performed with a transformer configuration of contacts. We interpret the experimental data on the basis of large-scale Langevin dynamical simulations of a three dimensional (3D) Josephson lattice with a current bias through a single plane. We show that the experimentally observed effects can be attributed to linking thermal vortex loop excitations that cause voltages in neighboring superconducting planes to lock in a narrow temperature range near the 3D phase transition.