title: Dimensionality Controlled Octahedral Symmetry-Mismatch and Functionalities in Epitaxial LaCoO₃/SrTiO₃ Heterostructures.
abstract: Epitaxial strain provides a powerful approach to manipulate physical properties of materials through rigid compression or extension of their chemical bonds via lattice-mismatch. Although symmetry-mismatch can lead to new physics by stabilizing novel interfacial structures, challenges in obtaining atomic-level structural information as well as lack of a suitable approach to separate it from the parasitical lattice-mismatch have limited the development of this field. Here, we present unambiguous experimental evidence that the symmetry-mismatch can be strongly controlled by dimensionality and significantly impact the collective electronic and magnetic functionalities in ultrathin perovskite LaCoO3/SrTiO3 heterojunctions. State-of-art diffraction and microscopy reveal that symmetry breaking dramatically modifies the interfacial structure of CoO6 octahedral building-blocks, resulting in expanded octahedron volume, reduced covalent screening, and stronger electron correlations. Such phenomena fundamentally alter the electronic and magnetic behaviors of LaCoO3 thin-films. We conclude that for epitaxial systems, correlation strength can be tuned by changing orbital hybridization, thus affecting the Coulomb repulsion, U, instead of by changing the band structure as the common paradigm in bulks. These results clarify the origin of magnetic ordering for epitaxial LaCoO3 and provide a route to manipulate electron correlation and magnetic functionality by orbital engineering at oxide heterojunctions.
authors.affiliation: †School of Materials, The University of Manchester, Manchester, M13 9PL, United Kingdom.
authors.forename: Liang
authors.initials: L
authors.lastname: Qiao
authors.forename: Jae Hyuck
authors.initials: JH
authors.lastname: Jang
authors.forename: David J
authors.initials: DJ
authors.lastname: Singh
authors.forename: Zheng
authors.initials: Z
authors.lastname: Gai
authors.forename: Haiyan
authors.initials: H
authors.lastname: Xiao
authors.affiliation: ⊥Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States.
authors.forename: Apurva
authors.initials: A
authors.lastname: Mehta
authors.forename: Rama K
authors.initials: RK
authors.lastname: Vasudevan
authors.forename: Alexander
authors.initials: A
authors.lastname: Tselev
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Feng
authors.forename: Hua
authors.initials: H
authors.lastname: Zhou
authors.affiliation: ○School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, NSW Australia.
authors.forename: Sean
authors.initials: S
authors.lastname: Li
authors.affiliation: ◆Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, Normandie Université, 6 Bd Maréchal Juin, F-14050 Caen Cedex 4, France.
authors.forename: Wilfrid
authors.initials: W
authors.lastname: Prellier
authors.forename: Xiaotao
authors.initials: X
authors.lastname: Zu
authors.affiliation: ¶Department of Physics, Lanzhou City University, Lanzhou 730070, China.
authors.forename: Zijiang
authors.initials: Z
authors.lastname: Liu
authors.forename: Albina
authors.initials: A
authors.lastname: Borisevich
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Baddorf
authors.forename: Michael D
authors.initials: MD
authors.lastname: Biegalski
keywords: LaCoO3; octahedral distortion; oxide heterostructures; symmetry mismatch