Effects of epitaxial strain and oxygen underdoping on order parameter competition in manganite/cuprate thin-film heterostructures*

To distinguish the role of magnetism from other factors that affect superconductivity in c-axis La_2/3Ca_1/3MnO₃/YBa₂Cu₃O_7-δ(LCMO/YBCO) heterostructures, we grow and characterize various perovskite/YBCO/perovskite trilayers, using ferromagnetic LCMO, paramagnetic LaNiO₃ (LNO), and orthorhombic PrBa₂Cu₃O_7-δ (PBCO) as the sandwiching layers. LCMO and LNO trilayers show similarly large superconducting T_c reductions with decreasing YBCO layer thickness, whereas this T_c reduction is not seen in the PBCO trilayers. Our results indicate that epitaxial strain has a stronger effect on the T_c of LCMO/YBCO heterostructures than any long-range magnetic proximity effect present. Using this system, we also study how the T_c reduction varies with oxygen underdoping by deoxygenating the cuprate layer. [1] We discuss our results in the wider context of multiple competing orders, in particular the recent observation by resonant x-ray scattering of robust charge-density-wave order in LCMO/YBCO multilayers. [2]
[1] H. Zhang et al., arXiv:1710.10668v1 [cond-mat.supr-con]
[2] A. Frano et. al., Nat. Materials 15:831 (2016)