title: Orbital reflectometry of oxide heterostructures.
abstract: The occupation of d orbitals controls the magnitude and anisotropy of the inter-atomic electron transfer in transition-metal oxides and hence exerts a key influence on their chemical bonding and physical properties. Atomic-scale modulations of the orbital occupation at surfaces and interfaces are believed to be responsible for massive variations of the magnetic and transport properties, but could not thus far be probed in a quantitative manner. Here we show that it is possible to derive quantitative, spatially resolved orbital polarization profiles from soft-X-ray reflectivity data, without resorting to model calculations. We demonstrate that the method is sensitive enough to resolve differences of ~3% in the occupation of Ni e(g) orbitals in adjacent atomic layers of a LaNiO(3)-LaAlO(3) superlattice, in good agreement with ab initio electronic-structure calculations. The possibility to quantitatively correlate theory and experiment on the atomic scale opens up many new perspectives for orbital physics in transition-metal oxides.
authors.forename: Eva
authors.initials: E
authors.lastname: Benckiser
authors.forename: Maurits W
authors.initials: MW
authors.lastname: Haverkort
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brück
authors.forename: Eberhard
authors.initials: E
authors.lastname: Goering
authors.forename: Sebastian
authors.initials: S
authors.lastname: Macke
authors.forename: Alex
authors.initials: A
authors.lastname: Frañó
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Yang
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
authors.forename: Georg
authors.initials: G
authors.lastname: Cristiani
authors.forename: Hanns-Ulrich
authors.initials: HU
authors.lastname: Habermeier
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Boris
authors.forename: Ioannis
authors.initials: I
authors.lastname: Zegkinoglou
authors.forename: Peter
authors.initials: P
authors.lastname: Wochner
authors.forename: Heon-Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Vladimir
authors.initials: V
authors.lastname: Hinkov
authors.forename: Bernhard
authors.initials: B
authors.lastname: Keimer