Pr-based perovskite cobaltites such as (Pr_1-yY_y)_1-xCa_xCoO_3-δ exhibit coupled structural/spin-state/metal-insulator transitions driven by a unique Pr valence shift. This can be controlled via heteroepitaxial strain and even enhanced to room temperature [1]. Here, we explore structural and transport behavior of epitaxial heterostructures of these materials, such as (Pr_1-yY_y)_1-xCa_xCoO_3-δ/Pr_1-xCa_xCoO_3-δ bilayers. The individual layers are found to exhibit decoupled transition temperatures for the valence/structural/spin-state/metal-insulator transitions. Surprisingly, however, bilayers have much lower low-temperature resistivity than the single-layer components, implying that metallic states arise at their interfaces. We study this behavior as a function of composition and layer thicknesses, discussing the results in terms of novel temperature-dependent interfacial charge transfer arising due to Pr valence shifts.   

[1] Chaturvedi et al., Nat. Commun. 13, 7774 (2022).