Resistances that exceed the Mott-Ioffe-Regel limit, known as bad metal
behavior, and non-Fermi liquid behavior are ubiquitous features of the normal
state of many strongly correlated materials. Here we establish the conditions
that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a
prototype, bandwidth-controlled metal-insulator transition. We show that
resistance saturation is determined by the magnitude of the Ni eg orbital
splitting, which can be tuned by strain in epitaxial films, causing the
appearance of bad metal behavior under certain conditions. The results shed
light on the nature of a crossover to non-Fermi liquid metal phase and provide
a predictive criterion for strong localization. They elucidate a seemingly
complex phase behavior as a function of film strain and confinement and provide
guidelines for orbital engineering and novel devices.Comment: Manuscript text, 5 figures and supplemen
