Strain-driven attenuation of superconductivity in heteroepitaxial perovskite/YBCO/perovskite thin films

To distinguish between the effects of strain and magnetism on the superconductivity in c-axis La_2/3Ca_1/3MnO₃/YBa₂Cu₃O_7-δ (LCMO/YBCO) heterostructures, we study perovskite/YBCO/perovskite thin films using either ferromagnetic LCMO or paramagnetic LaNiO₃ (LNO) as perovskite. For a lattice-symmetry matched comparison, we also use orthorhombic PrBa₂Cu₃O_7-δ (PBCO) in place of the pseudocubic perovskites. Unlike PBCO/YBCO/PBCO, both LCMO/YBCO/LCMO and LNO/YBCO/LNO trilayers show strong attenuation of the superconducting T_c as YBCO layer thickness is reduced from 21.4 to 5.4 nm. Our results indicate that heteroepitaxial strain, rather than long-range proximity effect, is responsible for the long length scales of T_c attenuation observed in c-axis LCMO/YBCO heterostructures [1].
[1] H. Zhang et al., https://arxiv.org/abs/1710.10668