Observing structural distortions in a LaMnO3 bilayer heterostructure on various [111] oriented substrates

Structural coupling in oxide perovskite heterostructures provides a route for engineering electronic properties. Additionally, alternative crystal orientations, such as the [111] direction, offer an additional degree of freedom for tuning these properties. These concepts merge in the experimental realization of a [111]-oriented bilayer, which, assuming a cubic crystal structure, is theoretically predicted to exhibit a Chern insulating phase due to the C3v symmetry. However, deviations from the cubic crystal structure in the form of crystal distortions, such as the Jahn-Teller distortions, break the C3v symmetry and suppress the Chern insulating phase. Here, we investigate the structural properties of LaMnO3 bilayer heterostructures, and thin films on LaAlO3, SrTiO3, and DyScO3 [111]-oriented substrates deposited by pulsed laser deposition. Scanning transmission electron microscopy confirms the bilayer structure and reveals the presence of distortions from the cubic symmetry, indirectly suggesting the presence of Jahn-Teller distortions, on LaAlO3 and DyScO3. On SrTiO3 the observed distortions are significantly suppressed. We quantify these distortions and demonstrate that their magnitude varies with strain and substrate coupling.