Improved conduction and orbital polarization in ultrathin LaNiO₃ sublayer by modulating octahedron rotation in LaNiO₃/CaTiO₃ superlattices.

ABSTRACT: Artificial oxide heterostructures have provided promising platforms for the exploration of emergent quantum phases with extraordinary properties. Here, we demonstrate an approach to stabilize a distinct oxygen octahedron rotation (OOR) characterized by a - a - c + in the ultrathin LaNiO₃ sublayers of the LaNiO₃/CaTiO₃ superlattices. Unlike the a - a - c - OOR in the LaNiO₃ bare film, the a - a - c + OOR favors high conductivity, driving the LaNiO₃ sublayer to a metallic state of ~100 K even when the layer thickness is as thin as 2 unit cells (u.c.). Simultaneously, strongly preferred occupation of d x 2 - y 2 orbital is achieved in LaNiO₃ sublayers. The largest change of occupancy is as high as 35%, observed in the 2 u.c.-thick LaNiO₃ sublayers sandwiched between 4 u.c.-thick CaTiO₃ sublayers. X-ray absorption spectra indicate that the a - a - c + OOR pattern of LaNiO₃ achieved in the LaNiO₃/CaTiO₃ heterostructures has significantly enhanced the Ni-3d/O-2p hybridization, stabilizing the metallic phase in ultrathin LaNiO₃ sublayers. The present work demonstrates that modulating the mode of OOR through heteroepitaxial synthesis can modify the orbital-lattice correlations in correlated perovskite oxides, revealing hidden properties of the materials.

SUBMITTER: Shi W 

PROVIDER: S-EPMC11567965 | biostudies-literature | 2024 Nov

REPOSITORIES: biostudies-literature