Superconducting transition in wire network under spatially modulated magnetic field

Superconducting wire network subjected to a uniform and a checkerboard-patterned magnetic field is investigated. The checkerboard field is created by an array of ferromagnetic dots placed on top of the superconducting network. The superconducting transition at α=1/2α=1/2 (α being the frustration parameter) is studied in detail by measuring the current–voltage (I–V) characteristics. The vortex configuration in this case is doubly degenerate. We investigated the change of the transition according to lifting this degeneracy by applying the checkerboard field. The results are consistent with the scenario proposed by Korshnov [S.E. Korshnov, Phys. Rev. Lett. 88 (2002) 167007].