title: Dimensionality control of d-orbital occupation in oxide superlattices.
abstract: Manipulating the orbital state in a strongly correlated electron system is of fundamental and technological importance for exploring and developing novel electronic phases. Here, we report an unambiguous demonstration of orbital occupancy control between t2g and eg multiplets in quasi-two-dimensional transition metal oxide superlattices (SLs) composed of a Mott insulator LaCoO3 and a band insulator LaAlO3. As the LaCoO3 sublayer thickness approaches its fundamental limit (i.e. one unit-cell-thick), the electronic state of the SLs changed from a Mott insulator, in which both t2g and eg orbitals are partially filled, to a band insulator by completely filling (emptying) the t2g (eg) orbitals. We found the reduction of dimensionality has a profound effect on the electronic structure evolution, which is, whereas, insensitive to the epitaxial strain. The remarkable orbital controllability shown here offers a promising pathway for novel applications such as catalysis and photovoltaics, where the energy of d level is an essential parameter.
authors.affiliation: 1] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [2] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: Da Woon
authors.initials: DW
authors.lastname: Jeong
authors.affiliation: 1] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States [2] Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Korea.
authors.forename: Woo Seok
authors.initials: WS
authors.lastname: Choi
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okamoto
authors.affiliation: Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Physics, Chungbuk National University, Cheongju 361-763, Korea.
authors.forename: Kyung Wan
authors.initials: KW
authors.lastname: Kim
authors.affiliation: Department of Physics, Hanyang University, Seoul 133-791, Korea.
authors.forename: Soon Jae
authors.initials: SJ
authors.lastname: Moon
authors.affiliation: 1] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [2] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea [3] Department of Physics, Chonbuk National University, Jeonju 561-756, Korea.
authors.forename: Deok-Yong
authors.initials: DY
authors.lastname: Cho
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
authors.forename: Ho Nyung
authors.initials: HN
authors.lastname: Lee
authors.affiliation: 1] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [2] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: Tae Won
authors.initials: TW
authors.lastname: Noh