Layer Stacking Dependent Suppression of Metallicity and Superconductivity in Sr ₂ IrO ₄ /YBa ₂ Cu ₃ O ₇ Bilayers

Abstract Epitaxial thin‐film heterostructures of the strongly spin‐orbit coupled Mott‐insulator Sr ₂ IrO ₄ (SIO) and the cuprate high temperature superconductor YBa ₂ Cu ₃ O _{7 − δ} (YBCO) are grown with pulsed laser deposition (PLD). A high crystalline quality is confirmed with X ray diffraction. The magnetic order of single SIO layers is studied with dc magnetization and low‐energy muon spin rotation measurements and resembles that of the bulk material with a canted antiferromagnetic order. The electronic normal state and superconducting properties of YBCO (10, 12, or 14 nm)–SIO (20 nm) and inversely stacked SIO (20nm)–YBCO (10, 12, or 14 nm) bilayers are studied with dc resistivity measurements and found to be strongly dependent on the sequence of the layer stacking. The YBCO–SIO bilayers with d ( YBCO ) = 14nm, 12 nm, and 10 nm are all metallic and superconducting with an onset temperature around 85K and zero resistivity below 65K. To the contrary, for the inversely stacked SIO–YBCO bilayers a metallic and superconducting response occurs only at d ( YBCO ) = 14 nm, whereas and 10 nm are electronic insulators. This highlights that a long‐ranged localization and/or depletion of the YBCO charge carriers occurs at the SIO–YBCO interface that is very anomalous and remains to be understood.