Matching in YBCO nanobridges due to surface barrier effects

The critical current density jc of YBa2Cu3O7−δ (YBCO) nanobridges (width ≈200 nm) is measured as a function of the magnetic flux density B, applied perpendicular to the YBCO-film plane. The resulting jc-vs-B characteristics, when analyzed in detail, exhibit a periodic modulation, which can be attributed to an enhanced stability of specific flux-line configurations. Such an increased stability is found for magnetic fields leading to a vortex lattice being commensurable with the width of the bridge and, thus, with the surface barriers at its edges. The magnitude of this new type of matching with perpendicular field orientation appears to be significantly smaller than what has been found in previously reported cases of parallel fields.