Interface‐Engineered Oxygen Reordering for Boosting Superconductivity in Ultrathin YBa ₂ Cu ₃ O 7–δ Nanostructures

Realizing high performance cuprate high‐temperature superconducting nanostructures for quantum devices requires overcoming the intrinsic instability of oxygen sublattices during nanofabrication. In cuprates, the disruption of oxygen stoichiometry and ordering represents a critical bottleneck, often resulting in suppression of superconductivity at the nanoscale. Here, we present an interface‐engineered strategy utilizing a dense Al 2 O 3 barrier layer for recovering superconductivity in ultrathin YBa 2 Cu 3 O 7–δ (YBCO) nanostructures via post‐annealing. This interfacial architecture creates a confined environment that effectively suppresses oxygen out‐diffusion while allowing oxygen redistribution within the YBCO lattice during annealing. The resulting nanostructures exhibit superior superconducting properties, highlighted by a two‐fold enhancement of the critical current in 5‐nm‐thick YBCO nanostructures and the achievement of a record‐low 12 nm lateral damage width. Notably, this strategy is validated across diverse geometries of the ultrathin YBCO nanostructures. Combined transport and structural characterizations point to improved oxygen ordering within the YBCO lattice as the modulation mechanism. More broadly, this versatile strategy for oxygen‐specific manipulation via interface design provides a general route to preserve electronic integrity in complex oxide nanodevices, opening new avenues for the exploration of correlated electron physics at the extreme nanoscale.