Schedule Feb 12, 2010
Optical Probe of Strong Correlations in LaNiO3 Thin Films and Superlattices
Maggie Stewart (UCSD)

M. K. Stewart1, J. Liu2, R. K. Smith1, B. C. Chapler1, C. Yee3, K. Haule3, J. Chakhalian2, and D. N. Basov1
1Department of Physics, University of California-San Diego
2Department of Physics, University of Arkansas
3Department of Physics, Rutgers University

We present an optical study of LaNiO3 in the range between 10 meV and 6 eV. Thin films of varying thickness were epitaxially grown by pulsed laser deposition on LaAlO3 and SrTiO3 substrates. The samples were investigated using near-normal incidence reflectance and variable angle spectroscopic ellipsometry at temperatures ranging from 20 K to 298 K. Several interband transitions are evident in the optical conductivity above 1 eV, in good agreement with band structure calculations. No Drude peak is observed however, in stark contrast with theoretical works predicting a finite density of states at the Fermi energy. This experimental finding of a vanishing Drude spectral weight, compared to a finite electron kinetic energy obtained from band structure calculations, is indicative of strong electronic correlations in LaNiO3. Optical conductivity of LaNiO3/LaAlO3 superlattices reveals small changes in the band structure of LaNiO3 induced by heterostructuring.

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