High critical current densities observed in PrBa_2Cu_3O_(7-δ)/YBa_2Cu_3O_(7-δ)/PrBa_2Cu_3O_(7-δ) ultrathin film constrictions

摘要

An original process has been developed for fabricating 0.45 X 0.45 μm~2 constrictions with normal metal banks using stacked YBa_2Cu_3O_(7-δ) and PrBa_2Cu_3O_(7-δ) ultrathin films. High values of critical temperature T_c ≈ 89 K and critical current densities J_C ≈ 2 X 10~7 A/cm~2 at 77 K were measured on 17 nm thick YBa_2Cu_3O_(7-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 PrBa_2Cu_3O_(7-δ) buffer and overlayer in YBa_2Cu_3O_(7-δ) constrictions is confirmed. Such YBa_2Cu_3O_(7-δ) nanowires are shown well adapted to phase-slip based devices and expected to fulfill the performances required in high frequency applications.