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Originally published in Science Express on 11 October 2007
Science 16 November 2007:
Vol. 318. no. 5853, pp. 1114 - 1117
DOI: 10.1126/science.1149338
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Research Articles

Orbital Reconstruction and Covalent Bonding at an Oxide Interface

J. Chakhalian,1,2* J. W. Freeland,3 H.-U. Habermeier,2 G. Cristiani,2 G. Khaliullin,2 M. van Veenendaal,3,4 B. Keimer2

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.

1 University of Arkansas, Fayetteville, AR 72701, USA.
2 Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany.
3 Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
4 Department of Physics, Northern Illinois University, Dekalb, IL 60115, USA.

* To whom correspondence should be addressed. E-mail: jchakhal{at}uark.edu

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