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.
Author entry (protected)