Session B34: Focus Session: Interfaces in Complex Oxides - Spectroscopy and Growth

11:15 AM–2:15 PM, Monday, March 21, 2011
Room: C141

Chair: John Hill, Brookhaven National Laboratory

Abstract ID: BAPS.2011.MAR.B34.4

Abstract: B34.00004 : Orbital Control in single unit cell LaNiO3/LaAlO3 superlattices

11:51 AM–12:03 PM

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Authors:

J.W. Freeland
(Argonne National Laboratory)

J. Liu
B. Gray
(University of Arkansas)

M. Kareev
(University of Arkansas)

J.W. Kim
(Argonne National Laboratory)

P.J. Ryan
(Argonne National Laboratory)

R. Pentcheva
(University of Munich)

J. Chakhalian
(University of Arkansas)

Oxide heterostructures built from strongly correlated electron materials offers unique opportunity to generate new ground-states by altering the balance of competing energies in the system. In pursuit of rational control of orbital polarization, we present a combined experimental and theoretical study of single unit cell LaNiO$_3$/LaAlO$_3$ superlattices[1]. Polarized x-ray absorption spectra show a distinct asymmetry in the orbital response under tensile vs. compressive strain. A splitting of orbital energies $\sim$100 meV with octahedral distortions is found for the case of compressive strain which is much smaller than the $3d$ bandwidth. In sharp contrast, for tensile strain, no splitting is found although a strong orbital polarization is still present. Density functional theory calculations of the electronic properties reveal that the asymmetry results from a combination of strain effects and altered covalency in the bonding across the interfacial apical oxygen to the Al site, leading to the opening of a pseudogap in the heterostructure for tensile strain. Work at Argonne, including the Advanced Photon, is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. [1] J.W. Freeland et. al. arXiv:1008.5618

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.B34.4