Superconducting properties of YBCO/LaNiO3 bilayers grown on (100) SrTiO3 substrates

High-Tc superconducting YBa2Cu3Oy/ LaNiO3 (YBCO/LNO) bilayers were grown by off axis magnetron sputtering on (100) SrTiO3 substrates. Patterned samples with YBCO thicknesses of 50–100 nm and a fixed 20 nm LNO capping layer were measured with magnetic fields applied parallel to the c axis and within the ab plane. Relative to well-studied single-layer YBCO, the bilayers exhibit a systematic suppression of superconductivity. Both the superconducting transition temperature (Tc) and the thermally activated flux-flow (TAFF) activation energy (U) decrease with decreasing YBCO thickness. The scaling of U(H) together with the temperature dependence of Hc2(T) near Tc is consistent with quasi-two-dimensional superconductivity confined at the YBCO/LNO interface. We attribute this behavior to interfacial strain- and redox–driven oxygen redistribution during LNO deposition, possibly accompanied by limited Ni intermixing, which together create a nanometer-scale region of reduced dimensionality and lower Tc. Interfacial superconductivity is established in oxide heterostructures and often shows quasi-two-dimensional behavior. Within this context, we present evidence consistent with quasi-2D behavior near Tc and discuss an interface-driven scenario in cuprate–nickelate bilayers. Given theoretical proposals that LaNiO3 heterostructures could host nontrivial band topology under suitable conditions, these results motivate further tests for possible topological superconductivity in this platform.