title: Orbital engineering in symmetry-breaking polar heterostructures.
abstract: We experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. In contrast to methods using strain or confinement, this orbital tuning is achieved by exploiting charge transfer and inversion symmetry breaking using atomically layered heterostructures. We illustrate the technique in the LaTiO_{3}-LaNiO_{3}-LaAlO_{3} system; a combination of x-ray absorption spectroscopy and ab initio theory reveals electron transfer and concomitant polar fields, resulting in a ∼50% change in the occupation of Ni d orbitals. This change is sufficiently large to remove the orbital degeneracy of bulk LaNiO_{3} and creates an electronic configuration approaching a single-band Fermi surface. Furthermore, we theoretically show that such three-component heterostructuring is robust and tunable by choice of insulator in the heterostructure, providing a general method for engineering orbital configurations and designing novel electronic systems.
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
authors: Ankit S
authors: AS
authors: Disa
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
authors: Divine P
authors: DP
authors: Kumah
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
authors: Andrei
authors: A
authors: Malashevich
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA and Department of Physics, Columbia University, New York, New York 10027, USA and Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.
authors: Hanghui
authors: H
authors: Chen
authors: National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors: Dario A
authors: DA
authors: Arena
authors: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Eliot D
authors: ED
authors: Specht
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA and Departments of Physics and Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors: Sohrab
authors: S
authors: Ismail-Beigi
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
authors: F J
authors: FJ
authors: Walker
authors: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA and Departments of Physics and Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06511, USA.
authors: Charles H
authors: CH
authors: Ahn