High critical current densities observed in PrBa2Cu3O7−δ∕YBa2Cu3O7−δ∕PrBa2Cu3O7−δ ultrathin film constrictions

Abstract

An original process has been developed for fabricating 0.45×0.45μm2 constrictions with normal metal banks using stacked YBa2Cu3O7−δ and PrBa2Cu3O7−δ ultrathin films. High values of critical temperature Tc≈89K and critical current densities Jc≈2×107A∕cm2 at 77K were measured on 17nm thick YBa2Cu3O7−δ, after the complete fabrication on MgO substrate. The observed robust superconducting properties of the device under applied magnetic field are attributed to large edge barriers opposed to vortex entry inside the nanobridge section. As there is no apparent degradation of the superconducting properties after long time storage, the benefit of using ultrathin PrBa2Cu3O7−δ buffer and overlayer in YBa2Cu3O7−δ constrictions is confirmed. Such YBa2Cu3O7−δ nanowires are shown well adapted to phase-slip based devices and expected to fulfill the performances required in high frequency applications.