Optical probe of strong correlations in LaNiO3 thin films

The optical properties of LaNiO3 thin films are investigated over a wide energy and temperature range. Thin films of varying thickness were grown by pulsed laser deposition on LaAlO3 and SrTiO3 substrates. The optical conductivity data of the films reveal a number of interband transitions above 1 eV, which are in good agreement with band structure calculations. No well defined Drude peak is observed; however, in stark contrast with local-density approximation theory 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, highlights the importance of strong electronic correlations in LaNiO3.