M. van Veenendaal

Orbital reconstruction and covalent bonding at an oxide interface.

Orbital reconstructions and covalent bonding must be considered as important factors in the rational design of oxide heterostructures with engineered physical properties. We have investigated the interface between high-temperature superconducting (Y,Ca)Ba2Cu3O7 and metallic La0.67Ca0.33MnO3 by resonant x-ray spectroscopy. A charge of about –0.2 electron is transferred from Mn to Cu ions across the interface and induces a major reconstruction of the orbital occupation and orbital symmetry in the interfacial CuO2 layers. In particular, the Cu d3z2–r2 orbital, which is fully occupied and electronically inactive in the bulk, is partially occupied at the interface. Supported by exact-diagonalization calculations, these data indicate the formation of a strong chemical bond between Cu and Mn atoms across the interface. Orbital reconstructions and associated covalent bonding are thus important factors in determining the physical properties of oxide heterostructures.

Magnetic excitation spectra of Sr2IrO4 probed by resonant inelastic x-ray scattering: establishing links to cuprate superconductors.

Jungho Kim, D. Casa, M. H. Upton, T. Gog, Young-June Kim, J. F. Mitchell, M. van Veenendaal, M. Daghofer, J. van den Brink, G. Khaliullin, B. J. Kim Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7 Material Science Division, Argonne National Laboratory, Argonne, IL 60439, USA Department of Physics, Northern Illinois University, De Kalb, IL 60115, USA Institute for Theoretical Solid Sate Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany and Max Planck Institute for Solid State Research, Heisenbergstrae 1, D-70569 Stuttgart, Germany (Dated: December 11, 2012)

Soft x-ray resonant diffraction study of magnetic and orbital correlations in a manganite near half doping

We have utilized resonant x-ray diffraction at the Mn L(II,III) edges in order to directly compare magnetic and orbital correlations in Pr0.6Ca0.4MnO3. Comparing the widths of the magnetic and orbital diffraction peaks, we find that the magnetic correlation length exceeds that of the orbital order by nearly a factor of 2. Furthermore, we observe a large (approximately 3 eV) spectral weight shift between the magnetic and orbital resonant line shapes, which cannot be explained within the classic Goodenough picture of a charge-ordered ground state. To explain the shift, we calculate the orbital and magnetic resonant diffraction line shapes based on a relaxed charge-ordered model.

Quantum confinement of Mott electrons in ultrathin LaNiO3/LaAlO3 superlattices

We investigate the electronic reconstruction in (LaNiO3)n/(LaAlO3)3 (n =3, 5 and 10) superlattices due to the quantum confinement (QC) by d.c. transport and resonant soft x-ray absorption spectroscopy. In proximity to the QC limit, a Mott-type transition from an itinerant electron behavior to a localized state is observed. The system exhibits tendency towards charge-order during the transition. ab initio cluster calculations are in good agreement with the absorption spectra, indicating that the apical ligand hole density is highly suppressed resulting in a strong modification of the electronic structure. At the dimensional crossover cellular dynamicalmean- field calculations support the emergence of a Mott insulator ground state in the heterostructured ultra-thin slab of LaNiO3.

Doping dependence ofNi 2px-ray-absorption spectra ofMxNi1−xO(M=Li,Na)

In this paper we give a description of the doping dependence of the Ni 2p x-ray-absorption spectra of MxNi1−xO (M=Li,Na). We will show that a description beyond an atomic-multiplet calculation is required. To study intermediate doping levels use will be made of a two-metal-site cluster, where one side functions as a hole reservoir. From this study it follows that holes are most likely on the oxygen atoms of the NiO6 units around the Li impurities

Pressure tuning of bond-directional exchange interactions and magnetic frustration in the hyperhoneycomb iridate β−Li2IrO3

We explore the response of Ir

Determining the electron-phonon coupling strength from Resonant Inelastic X-ray Scattering at transition metal L-edges

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Observation of phonons with resonant inelastic x-ray scattering

orbitals to pressure in

Using Nonequilibrium Dynamics to Probe Competing Orders in a Mott-Peierls System.

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BRANCHING RATIOS OF THE CIRCULAR DICHROISM AT RARE EARTH L23 EDGES

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