Resistive state triggered by vortex entry in YBa₂Cu₃O_7−δ nanostructures

Highlights: • We have fabricated YBCO nanowires with cross sections down to 50 × 50 nm². • We measured the R(T) of these nanowires close to the superconducting transition. • We analyzed the transition broadening with a thermally activated vortex entry model. • We extracted reasonable values of λ₀ = 270 nm and ξ₀ = 2 nm. • The λ₀ value is confirmed by the analyses of I_C(B) modulations in Dayem bridge nanoSQUIDs. - Abstract: We have realized YBa₂Cu₃O_7−δ nanowires and nano Superconducting Quantum Interference Devices (nanoSQUID). The measured temperature dependence of the wire resistances below the superconducting transition temperature has been analyzed using a thermally activated vortex entry model valid for wires wider than the superconducting coherence length. The extracted zero temperature values of the London penetration depth, λ₀≃270±15nm, are in good agreement with the value obtained from critical current modulations as a function of an externally applied magnetic field in a nanoSQUID implementing two nanowires