Epitaxial strain driven crossover from Drude to Drude-Smith terahertz conductivity dynamics in LaNiO thin films.

We investigate the hetero-epitaxial strain driven low-energy charge dynamics in compressive and tensile strained LaNiO thin films employing terahertz (THz) time-domain spectroscopy. The complex THz conductivity exhibits a crossover from Drude type metallic behavior for the compressive film to a Drude-Smith type disordered behavior for the tensile film. This demonstration of strain driven crossover in THz conductivity dynamics, while the two films have qualitatively similar dc conductivities, (i) brings out the potential of THz technology in distinguishing between similar dc electronic phases and (ii) suggests that LaNiO under compressive strain is a better candidate for applications as electrodes in oxides electronics.